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Sci.Electronics.Basics -> high-side current sensing chips

There are 24 messages in this thread.
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Author: gearhead
Date: 12:40 08-04-08

Hi all, I'd like to help out some friends on an antique motorcycle
forum that have a 6 volt regulator project. One of them built a
regulator on perfboard and posted the schematic. It has a couple of
things I'd tweak, but it works.
The main challenge: his regulator design doesn't incorporate current
limiting. Even the original relay-style mechanical regulators
incorporated current limiting, because the generators required it.
Somebody on the forum suggested the zxct1009, but it only comes in
surface mount which means we can't rejigger the existing perfboard
project to include the new chip. It would mean having a custom-
printed circuit board, and soldering techniques perhaps a little too
demanding for somebody building his first circuit -- which probably
describes a lot of the guys on the forum.
pdf of the circuit:
http://www.hydra-glide.com/phpBB2/download.php?id=1173
I've tried to find a through-hole component that fits the bill, but
can't seem to come up with anything just right. I saw the micrel
MIC5021, but it supposedly operates on 12 volts and up.
http://www.micrel.com/_PDF/mic5021.pdf
Now, perhaps they make that statement on the datasheet because the
chip actually also has a voltage doubler and the high side drive needs
that kind of voltage to turn on a mosfet, and it's possible the chip
itself will actually run on a much lower voltage. But the datasheet
doesn't say anything to this effect. Has anybody used the MIC5021 and
know if it might actually turn on at say 5 volts or perhaps know of
any other through hole chips for current sensing?

Author: Tim Wescott
Date: 13:03 08-04-08

gearhead wrote:
> Hi all, I'd like to help out some friends on an antique motorcycle
> forum that have a 6 volt regulator project. One of them built a
> regulator on perfboard and posted the schematic. It has a couple of
> things I'd tweak, but it works.
> The main challenge: his regulator design doesn't incorporate current
> limiting. Even the original relay-style mechanical regulators
> incorporated current limiting, because the generators required it.
> Somebody on the forum suggested the zxct1009, but it only comes in
> surface mount which means we can't rejigger the existing perfboard
> project to include the new chip. It would mean having a custom-
> printed circuit board, and soldering techniques perhaps a little too
> demanding for somebody building his first circuit -- which probably
> describes a lot of the guys on the forum.
> pdf of the circuit:
> http://www.hydra-glide.com/phpBB2/download.php?id=1173
> I've tried to find a through-hole component that fits the bill, but
> can't seem to come up with anything just right. I saw the micrel
> MIC5021, but it supposedly operates on 12 volts and up.
> http://www.micrel.com/_PDF/mic5021.pdf
> Now, perhaps they make that statement on the datasheet because the
> chip actually also has a voltage doubler and the high side drive needs
> that kind of voltage to turn on a mosfet, and it's possible the chip
> itself will actually run on a much lower voltage. But the datasheet
> doesn't say anything to this effect. Has anybody used the MIC5021 and
> know if it might actually turn on at say 5 volts or perhaps know of
> any other through hole chips for current sensing?

This is just a suggestion, but consider the circuit below. If the
transistors are well matched Vchg should come pretty close to Vgen/10 +
47 * 0.02 * Ibatt -- and you can jigger your component values around to
change the numbers. You'll _probably_ be able to make this work OK with
any two unmatched (but like part-number) PNP transistors, like 2N3904's,
but you'd do better to get a matched pair (DigiKey has some Zetex parts
that would do, if there are any through-hole ones).

Try this out with SPICE before you run with it: I just threw it down off
the top of my head, it's not exactly like anything I've done before nor
is it tested at all.

Vgen ___ Vbatt
o-----o---|___|---o-----o
| | ----->
| 0.02 | Ibatt
.-. .-.
| |100 | |100
| | | |
'-' '-'
| |
| |
>| |<
|---o---|
/| | |\
| | |
| | |
Vchg | '-----o
o-----o |
| |
.-. .-.
| |4.7K | |47K
| | | |
'-' '-'
| |
| |
=== ===
GND GND
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

Author: petrus bitbyter
Date: 16:30 08-04-08

"gearhead" <nospam@billburg.com> schreef in bericht
news:e66fa9e8-d621-4ba3-8c47-fc5752b3f045@m36g2000hse.googlegroups.com...
> Hi all, I'd like to help out some friends on an antique motorcycle
> forum that have a 6 volt regulator project. One of them built a
> regulator on perfboard and posted the schematic. It has a couple of
> things I'd tweak, but it works.
> The main challenge: his regulator design doesn't incorporate current
> limiting. Even the original relay-style mechanical regulators
> incorporated current limiting, because the generators required it.
> Somebody on the forum suggested the zxct1009, but it only comes in
> surface mount which means we can't rejigger the existing perfboard
> project to include the new chip. It would mean having a custom-
> printed circuit board, and soldering techniques perhaps a little too
> demanding for somebody building his first circuit -- which probably
> describes a lot of the guys on the forum.
> pdf of the circuit:
> http://www.hydra-glide.com/phpBB2/download.php?id=1173
> I've tried to find a through-hole component that fits the bill, but
> can't seem to come up with anything just right. I saw the micrel
> MIC5021, but it supposedly operates on 12 volts and up.
> http://www.micrel.com/_PDF/mic5021.pdf
> Now, perhaps they make that statement on the datasheet because the
> chip actually also has a voltage doubler and the high side drive needs
> that kind of voltage to turn on a mosfet, and it's possible the chip
> itself will actually run on a much lower voltage. But the datasheet
> doesn't say anything to this effect. Has anybody used the MIC5021 and
> know if it might actually turn on at say 5 volts or perhaps know of
> any other through hole chips for current sensing?

That Micrel chip is not a current sensor, it is a mosfet driver. Looking for
a highside current sensor, try the MAX4374. A ZXCT1008 or ZXCT1009 may be
even better. But I doubt you to need that special (and expensive) chips.

Can't be sure what current you want to limit, but usually the field current
is limited to limit the output voltage of the generator. Which in turn
prevents the battery from being overloaded. This is exactly what the circuit
of your schematic is supposed to do. Just use R1 to set the correct voltage.
For a 6V lead-accid battery this will be about 6,9V. So even for fully
loaded battery the voltage should never exceed that value. You may have to
take some voltage loss accross D6 into account which is about 0.2V for this
particular diode.

petrus bitbyter

Author: gearhead
Date: 16:34 08-04-08

On Apr 8, 10:03=A0am, Tim Wescott <t...@seemywebsite.com> wrote:
> gearhead wrote:
> > Hi all, I'd like to help out some friends on an antique motorcycle
> > forum that have a 6 volt regulator project. =A0One of them built a
> > regulator on perfboard and posted the schematic. =A0It has a couple of
> > things I'd tweak, but it works.
> > The main challenge: =A0his regulator design doesn't incorporate current
> > limiting. =A0Even the original relay-style mechanical regulators
> > incorporated current limiting, because the generators required it.
> > Somebody on the forum suggested the zxct1009, but it only comes in
> > surface mount which means we can't rejigger the existing perfboard
> > project to include the new chip. =A0It would mean having a custom-
> > printed circuit board, and soldering techniques perhaps a little too
> > demanding for somebody building his first circuit -- which probably
> > describes a lot of the guys on the forum.
> > pdf of the circuit:
> >http://www.hydra-glide.com/phpBB2/download.php?id=3D1173
> > I've tried to find a through-hole component that fits the bill, but
> > can't seem to come up with anything just right. =A0I saw the micrel
> > MIC5021, but it supposedly operates on 12 volts and up.
> >http://www.micrel.com/_PDF/mic5021.pdf
> > Now, perhaps they make that statement on the datasheet because the
> > chip actually also has a voltage doubler and the high side drive needs
> > that kind of voltage to turn on a mosfet, and it's possible the chip
> > itself will actually run on a much lower voltage. =A0But the datasheet
> > doesn't say anything to this effect. =A0Has anybody used the MIC5021 and=

> > know if it might actually turn on at say 5 volts or perhaps know of
> > any other through hole chips for current sensing?
>
> This is just a suggestion, but consider the circuit below. =A0If the
> transistors are well matched Vchg should come pretty close to Vgen/10 +
> 47 * 0.02 * Ibatt -- and you can jigger your component values around to
> change the numbers. =A0You'll _probably_ be able to make this work OK with=

> any two unmatched (but like part-number) PNP transistors, like 2N3904's,
> but you'd do better to get a matched pair (DigiKey has some Zetex parts
> that would do, if there are any through-hole ones).
>
> Try this out with SPICE before you run with it: I just threw it down off
> the top of my head, it's not exactly like anything I've done before nor
> is it tested at all.
>
> =A0 =A0 =A0 Vgen =A0 =A0 =A0 =A0___ =A0 =A0 =A0 =A0Vbatt
> =A0 =A0 =A0 =A0o-----o---|___|---o-----o
> =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 | =A0 ----->
> =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 0.02 =A0 =A0| =A0 =A0Ibatt
> =A0 =A0 =A0 =A0 =A0 =A0 .-. =A0 =A0 =A0 =A0 .-.
> =A0 =A0 =A0 =A0 =A0 =A0 | |100 =A0 =A0 =A0| |100
> =A0 =A0 =A0 =A0 =A0 =A0 | | =A0 =A0 =A0 =A0 | |
> =A0 =A0 =A0 =A0 =A0 =A0 '-' =A0 =A0 =A0 =A0 '-'
> =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 |
> =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 |
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 >| =A0 =A0 =A0 |<
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0|---o---|
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 /| =A0 | =A0 |\
> =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 | =A0 =A0 |
> =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 | =A0 =A0 |
> =A0 =A0 =A0Vchg =A0 =A0| =A0 =A0 '-----o
> =A0 =A0 =A0 =A0o-----o =A0 =A0 =A0 =A0 =A0 |
> =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 |
> =A0 =A0 =A0 =A0 =A0 =A0 .-. =A0 =A0 =A0 =A0 .-.
> =A0 =A0 =A0 =A0 =A0 =A0 | |4.7K =A0 =A0 | |47K
> =A0 =A0 =A0 =A0 =A0 =A0 | | =A0 =A0 =A0 =A0 | |
> =A0 =A0 =A0 =A0 =A0 =A0 '-' =A0 =A0 =A0 =A0 '-'
> =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 |
> =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 |
> =A0 =A0 =A0 =A0 =A0 =A0 =3D=3D=3D =A0 =A0 =A0 =A0 =3D=3D=3D
> =A0 =A0 =A0 =A0 =A0 =A0 GND =A0 =A0 =A0 =A0 GND

I've done plenty of scheming about how to do it with discretes. But
like you said, I'd still want to use a chip in the end, to get matched
transistors. Pairs and arrays, I see ony surface mount, including
zetex.
If I have to go that way, might as well use the ZXCT1009F in SOT-23
with pins 1.9 mm apart according to the diagram. Almost a tenth of an
inch, could probably solder it right onto the pads of a perfboard, eh?

Author: gearhead
Date: 17:06 08-04-08

On Apr 8, 1:30=A0pm, "petrus bitbyter"
<pieterkraltlaatdit...@enditookhccnet.nl> wrote:
> "gearhead" <nos...@billburg.com> schreef in
berichtnews:e66fa9e8-d621-4ba3=
-8c47-fc5752b3f045@m36g2000hse.googlegroups.com...
>
>
>
>
>
> > Hi all, I'd like to help out some friends on an antique motorcycle
> > forum that have a 6 volt regulator project. =A0One of them built a
> > regulator on perfboard and posted the schematic. =A0It has a couple of
> > things I'd tweak, but it works.
> > The main challenge: =A0his regulator design doesn't incorporate current
> > limiting. =A0Even the original relay-style mechanical regulators
> > incorporated current limiting, because the generators required it.
> > Somebody on the forum suggested the zxct1009, but it only comes in
> > surface mount which means we can't rejigger the existing perfboard
> > project to include the new chip. =A0It would mean having a custom-
> > printed circuit board, and soldering techniques perhaps a little too
> > demanding for somebody building his first circuit -- which probably
> > describes a lot of the guys on the forum.
> > pdf of the circuit:
> >http://www.hydra-glide.com/phpBB2/download.php?id=3D1173
> > I've tried to find a through-hole component that fits the bill, but
> > can't seem to come up with anything just right. =A0I saw the micrel
> > MIC5021, but it supposedly operates on 12 volts and up.
> >http://www.micrel.com/_PDF/mic5021.pdf
> > Now, perhaps they make that statement on the datasheet because the
> > chip actually also has a voltage doubler and the high side drive needs
> > that kind of voltage to turn on a mosfet, and it's possible the chip
> > itself will actually run on a much lower voltage. =A0But the datasheet
> > doesn't say anything to this effect. =A0Has anybody used the MIC5021 and=

> > know if it might actually turn on at say 5 volts or perhaps know of
> > any other through hole chips for current sensing?
>
> That Micrel chip is not a current sensor, it is a mosfet driver. Looking f=
or
> a highside current sensor, try the MAX4374. A ZXCT1008 or ZXCT1009 may be
> even better. But I doubt you to need that special (and expensive) chips.
>
> Can't be sure what current you want to limit, but usually the field curren=
t
> is limited to limit the output voltage of the generator. Which in turn
> prevents the battery from being overloaded. This is exactly what the circu=
it
> of your schematic is supposed to do. Just use R1 to set the correct voltag=
e.
> For a 6V lead-accid battery this will be about 6,9V. So even for fully
> loaded battery the voltage should never exceed that value. You may have to=

> take some voltage loss accross D6 into account which is about 0.2V for thi=
s
> particular diode.
>
> petrus bitbyter- Hide quoted text -
>
> - Show quoted text -

Current limiting protects the generator, not the battery.

Author: gearhead
Date: 17:12 08-04-08

On Apr 8, 1:30=A0pm, "petrus bitbyter"
<pieterkraltlaatdit...@enditookhccnet.nl> wrote:
> "gearhead" <nos...@billburg.com> schreef in
berichtnews:e66fa9e8-d621-4ba3=
-8c47-fc5752b3f045@m36g2000hse.googlegroups.com...
>
>
>
>
>
> > Hi all, I'd like to help out some friends on an antique motorcycle
> > forum that have a 6 volt regulator project. =A0One of them built a
> > regulator on perfboard and posted the schematic. =A0It has a couple of
> > things I'd tweak, but it works.
> > The main challenge: =A0his regulator design doesn't incorporate current
> > limiting. =A0Even the original relay-style mechanical regulators
> > incorporated current limiting, because the generators required it.
> > Somebody on the forum suggested the zxct1009, but it only comes in
> > surface mount which means we can't rejigger the existing perfboard
> > project to include the new chip. =A0It would mean having a custom-
> > printed circuit board, and soldering techniques perhaps a little too
> > demanding for somebody building his first circuit -- which probably
> > describes a lot of the guys on the forum.
> > pdf of the circuit:
> >http://www.hydra-glide.com/phpBB2/download.php?id=3D1173
> > I've tried to find a through-hole component that fits the bill, but
> > can't seem to come up with anything just right. =A0I saw the micrel
> > MIC5021, but it supposedly operates on 12 volts and up.
> >http://www.micrel.com/_PDF/mic5021.pdf
> > Now, perhaps they make that statement on the datasheet because the
> > chip actually also has a voltage doubler and the high side drive needs
> > that kind of voltage to turn on a mosfet, and it's possible the chip
> > itself will actually run on a much lower voltage. =A0But the datasheet
> > doesn't say anything to this effect. =A0Has anybody used the MIC5021 and=

> > know if it might actually turn on at say 5 volts or perhaps know of
> > any other through hole chips for current sensing?
>
> That Micrel chip is not a current sensor, it is a mosfet driver. Looking f=
or
> a highside current sensor, try the MAX4374. A ZXCT1008 or ZXCT1009 may be
> even better. But I doubt you to need that special (and expensive) chips.
>
> Can't be sure what current you want to limit, but usually the field curren=
t
> is limited to limit the output voltage of the generator. Which in turn
> prevents the battery from being overloaded. This is exactly what the circu=
it
> of your schematic is supposed to do. Just use R1 to set the correct voltag=
e.
> For a 6V lead-accid battery this will be about 6,9V. So even for fully
> loaded battery the voltage should never exceed that value. You may have to=

> take some voltage loss accross D6 into account which is about 0.2V for thi=
s
> particular diode.
>
> petrus bitbyter- Hide quoted text -
>
> - Show quoted text -

Don't say the micrel chip is not a current sensor. It does current
sensing.
And current limiting is for the generator, not the battery.

Author: Wimpie
Date: 17:13 08-04-08

On 8 abr, 22:34, gearhead <nos...@billburg.com> wrote:
> On Apr 8, 10:03 am, Tim Wescott <t...@seemywebsite.com> wrote:
>
>
>
> > gearhead wrote:
> > > Hi all, I'd like to help out some friends on an antique motorcycle
> > > forum that have a 6 volt regulator project. One of them built a
> > > regulator on perfboard and posted the schematic. It has a couple of
> > > things I'd tweak, but it works.
> > > The main challenge: his regulator design doesn't incorporate current
> > > limiting. Even the original relay-style mechanical regulators
> > > incorporated current limiting, because the generators required it.
> > > Somebody on the forum suggested the zxct1009, but it only comes in
> > > surface mount which means we can't rejigger the existing perfboard
> > > project to include the new chip. It would mean having a custom-
> > > printed circuit board, and soldering techniques perhaps a little too
> > > demanding for somebody building his first circuit -- which probably
> > > describes a lot of the guys on the forum.
> > > pdf of the circuit:
> > >http://www.hydra-glide.com/phpBB2/download.php?id=1173
> > > I've tried to find a through-hole component that fits the bill, but
> > > can't seem to come up with anything just right. I saw the micrel
> > > MIC5021, but it supposedly operates on 12 volts and up.
> > >http://www.micrel.com/_PDF/mic5021.pdf
> > > Now, perhaps they make that statement on the datasheet because the
> > > chip actually also has a voltage doubler and the high side drive needs
> > > that kind of voltage to turn on a mosfet, and it's possible the chip
> > > itself will actually run on a much lower voltage. But the datasheet
> > > doesn't say anything to this effect. Has anybody used the MIC5021 and
> > > know if it might actually turn on at say 5 volts or perhaps know of
> > > any other through hole chips for current sensing?
>
> > This is just a suggestion, but consider the circuit below. If the
> > transistors are well matched Vchg should come pretty close to Vgen/10 +
> > 47 * 0.02 * Ibatt -- and you can jigger your component values around to
> > change the numbers. You'll _probably_ be able to make this work OK with
> > any two unmatched (but like part-number) PNP transistors, like 2N3904's,
> > but you'd do better to get a matched pair (DigiKey has some Zetex parts
> > that would do, if there are any through-hole ones).
>
> > Try this out with SPICE before you run with it: I just threw it down off
> > the top of my head, it's not exactly like anything I've done before nor
> > is it tested at all.
>
> > Vgen ___ Vbatt
> > o-----o---|___|---o-----o
> > | | ----->
> > | 0.02 | Ibatt
> > .-. .-.
> > | |100 | |100
> > | | | |
> > '-' '-'
> > | |
> > | |
> > >| |<
> > |---o---|
> > /| | |\
> > | | |
> > | | |
> > Vchg | '-----o
> > o-----o |
> > | |
> > .-. .-.
> > | |4.7K | |47K
> > | | | |
> > '-' '-'
> > | |
> > | |
> > === ===
> > GND GND
>
> I've done plenty of scheming about how to do it with discretes. But
> like you said, I'd still want to use a chip in the end, to get matched
> transistors. Pairs and arrays, I see ony surface mount, including
> zetex.
> If I have to go that way, might as well use the ZXCT1009F in SOT-23
> with pins 1.9 mm apart according to the diagram. Almost a tenth of an
> inch, could probably solder it right onto the pads of a perfboard, eh?

Hello,

When you buy about 10 general purpose PNP transistors from one batch,
you will probably find several transistors that are within some mV
with same Ic. When you design the 2 transistor current sensor at low
bias current, self heating can be neglected and it saves you from
soldering SMD devices like NXP's BCM857. When matching is impossible,
you might add a trimmer potentiometer for nulling.

best regards,

Wim
PA3DJS
www.tetech.nl
please remove abc from the address

Author: gearhead
Date: 17:32 08-04-08

On Apr 8, 2:13=A0pm, Wimpie <wimabc...@tetech.nl> wrote:
> On 8 abr, 22:34, gearhead <nos...@billburg.com> wrote:
>
>
>
>
>
> > On Apr 8, 10:03 am, Tim Wescott <t...@seemywebsite.com> wrote:
>
> > > gearhead wrote:
> > > > Hi all, I'd like to help out some friends on an antique motorcycle
> > > > forum that have a 6 volt regulator project. =A0One of them built a
> > > > regulator on perfboard and posted the schematic. =A0It has a couple
=
of
> > > > things I'd tweak, but it works.
> > > > The main challenge: =A0his regulator design doesn't incorporate
curr=
ent
> > > > limiting. =A0Even the original relay-style mechanical regulators
> > > > incorporated current limiting, because the generators required it.
> > > > Somebody on the forum suggested the zxct1009, but it only comes in
> > > > surface mount which means we can't rejigger the existing perfboard
> > > > project to include the new chip. =A0It would mean having a custom-
> > > > printed circuit board, and soldering techniques perhaps a little
too=

> > > > demanding for somebody building his first circuit -- which probably
> > > > describes a lot of the guys on the forum.
> > > > pdf of the circuit:
> > > >http://www.hydra-glide.com/phpBB2/download.php?id=3D1173
> > > > I've tried to find a through-hole component that fits the bill, but
> > > > can't seem to come up with anything just right. =A0I saw the micrel
> > > > MIC5021, but it supposedly operates on 12 volts and up.
> > > >http://www.micrel.com/_PDF/mic5021.pdf
> > > > Now, perhaps they make that statement on the datasheet because the
> > > > chip actually also has a voltage doubler and the high side drive
nee=
ds
> > > > that kind of voltage to turn on a mosfet, and it's possible the
chip=

> > > > itself will actually run on a much lower voltage. =A0But the
datashe=
et
> > > > doesn't say anything to this effect. =A0Has anybody used the
MIC5021=
and
> > > > know if it might actually turn on at say 5 volts or perhaps know of
> > > > any other through hole chips for current sensing?
>
> > > This is just a suggestion, but consider the circuit below. =A0If the
> > > transistors are well matched Vchg should come pretty close to Vgen/10 =
+
> > > 47 * 0.02 * Ibatt -- and you can jigger your component values around t=
o
> > > change the numbers. =A0You'll _probably_ be able to make this work OK =
with
> > > any two unmatched (but like part-number) PNP transistors, like 2N3904'=
s,
> > > but you'd do better to get a matched pair (DigiKey has some Zetex part=
s
> > > that would do, if there are any through-hole ones).
>
> > > Try this out with SPICE before you run with it: I just threw it down o=
ff
> > > the top of my head, it's not exactly like anything I've done before no=
r
> > > is it tested at all.
>
> > > =A0 =A0 =A0 Vgen =A0 =A0 =A0 =A0___ =A0 =A0 =A0 =A0Vbatt
> > > =A0 =A0 =A0 =A0o-----o---|___|---o-----o
> > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 | =A0 ----->
> > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 0.02 =A0 =A0| =A0 =A0Ibatt
> > > =A0 =A0 =A0 =A0 =A0 =A0 .-. =A0 =A0 =A0 =A0 .-.
> > > =A0 =A0 =A0 =A0 =A0 =A0 | |100 =A0 =A0 =A0| |100
> > > =A0 =A0 =A0 =A0 =A0 =A0 | | =A0 =A0 =A0 =A0 | |
> > > =A0 =A0 =A0 =A0 =A0 =A0 '-' =A0 =A0 =A0 =A0 '-'
> > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 |
> > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 |
> > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 >| =A0 =A0 =A0 |<
> > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0|---o---|
> > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 /| =A0 | =A0 |\
> > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 | =A0 =A0 |
> > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 | =A0 =A0 |
> > > =A0 =A0 =A0Vchg =A0 =A0| =A0 =A0 '-----o
> > > =A0 =A0 =A0 =A0o-----o =A0 =A0 =A0 =A0 =A0 |
> > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 |
> > > =A0 =A0 =A0 =A0 =A0 =A0 .-. =A0 =A0 =A0 =A0 .-.
> > > =A0 =A0 =A0 =A0 =A0 =A0 | |4.7K =A0 =A0 | |47K
> > > =A0 =A0 =A0 =A0 =A0 =A0 | | =A0 =A0 =A0 =A0 | |
> > > =A0 =A0 =A0 =A0 =A0 =A0 '-' =A0 =A0 =A0 =A0 '-'
> > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 |
> > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 |
> > > =A0 =A0 =A0 =A0 =A0 =A0 =3D=3D=3D =A0 =A0 =A0 =A0 =3D=3D=3D
> > > =A0 =A0 =A0 =A0 =A0 =A0 GND =A0 =A0 =A0 =A0 GND
>
> > I've done plenty of scheming about how to do it with discretes. =A0But
> > like you said, I'd still want to use a chip in the end, to get matched
> > transistors. =A0Pairs and arrays, I see ony surface mount, including
> > zetex.
> > If I have to go that way, might as well use the ZXCT1009F in SOT-23
> > with pins 1.9 mm apart according to the diagram. =A0Almost a tenth of an=

> > inch, could probably solder it right onto the pads of a perfboard, eh?
>
> Hello,
>
> When you buy about 10 general purpose PNP transistors from one batch,
> you will probably find several transistors that are within some mV
> with same Ic.

Doesn't gain determine the balance in a current mirror? If so, one
would have to match for gain. I did match for gain last time I
experimented with current mirrors. I'd like to hear from the experts
about the need for this.

> When you design the 2 transistor current sensor at low
> bias current, self heating can be neglected and it saves you from
> soldering SMD devices like NXP's BCM857. =A0When matching is impossible,
> you might add a trimmer potentiometer for nulling.
>
> best regards,
>
> Wim
> PA3DJSwww.tetech.nl

About temperature matching. I calculate that one tenth of a degree
centigrade difference between the transistors in a mirror would add
about one percent error to the current mirror. I wouldn't want
temperature vagaries causing any more error than that. I'm wondering
if you could count on discrete transistors on a board to stay within a
tenth of a degree to each other. More fodder for the experts.

Author: Wimpie
Date: 18:53 08-04-08

On 8 abr, 23:32, gearhead <nos...@billburg.com> wrote:
> On Apr 8, 2:13 pm, Wimpie <wimabc...@tetech.nl> wrote:
>
>
>
> > On 8 abr, 22:34, gearhead <nos...@billburg.com> wrote:
>
> > > On Apr 8, 10:03 am, Tim Wescott <t...@seemywebsite.com> wrote:
>
> > > > gearhead wrote:
> > > > > Hi all, I'd like to help out some friends on an antique
motorcycle
> > > > > forum that have a 6 volt regulator project. One of them built
a
> > > > > regulator on perfboard and posted the schematic. It has a
couple of
> > > > > things I'd tweak, but it works.
> > > > > The main challenge: his regulator design doesn't incorporate
current
> > > > > limiting. Even the original relay-style mechanical regulators
> > > > > incorporated current limiting, because the generators required
it.
> > > > > Somebody on the forum suggested the zxct1009, but it only comes
in
> > > > > surface mount which means we can't rejigger the existing
perfboard
> > > > > project to include the new chip. It would mean having a
custom-
> > > > > printed circuit board, and soldering techniques perhaps a
little too
> > > > > demanding for somebody building his first circuit -- which
probably
> > > > > describes a lot of the guys on the forum.
> > > > > pdf of the circuit:
> > > > >http://www.hydra-glide.com/phpBB2/download.php?id=1173
> > > > > I've tried to find a through-hole component that fits the bill,
but
> > > > > can't seem to come up with anything just right. I saw the
micrel
> > > > > MIC5021, but it supposedly operates on 12 volts and up.
> > > > >http://www.micrel.com/_PDF/mic5021.pdf
> > > > > Now, perhaps they make that statement on the datasheet because
the
> > > > > chip actually also has a voltage doubler and the high side
drive needs
> > > > > that kind of voltage to turn on a mosfet, and it's possible the
chip
> > > > > itself will actually run on a much lower voltage. But the
datasheet
> > > > > doesn't say anything to this effect. Has anybody used the
MIC5021 and
> > > > > know if it might actually turn on at say 5 volts or perhaps
know of
> > > > > any other through hole chips for current sensing?
>
> > > > This is just a suggestion, but consider the circuit below. If the
> > > > transistors are well matched Vchg should come pretty close to
Vgen/10 +
> > > > 47 * 0.02 * Ibatt -- and you can jigger your component values around
to
> > > > change the numbers. You'll _probably_ be able to make this work OK
with
> > > > any two unmatched (but like part-number) PNP transistors, like
2N3904's,
> > > > but you'd do better to get a matched pair (DigiKey has some Zetex
parts
> > > > that would do, if there are any through-hole ones).
>
> > > > Try this out with SPICE before you run with it: I just threw it down
off
> > > > the top of my head, it's not exactly like anything I've done before
nor
> > > > is it tested at all.
>
> > > > Vgen ___ Vbatt
> > > > o-----o---|___|---o-----o
> > > > | | ----->
> > > > | 0.02 | Ibatt
> > > > .-. .-.
> > > > | |100 | |100
> > > > | | | |
> > > > '-' '-'
> > > > | |
> > > > | |
> > > > >| |<
> > > > |---o---|
> > > > /| | |\
> > > > | | |
> > > > | | |
> > > > Vchg | '-----o
> > > > o-----o |
> > > > | |
> > > > .-. .-.
> > > > | |4.7K | |47K
> > > > | | | |
> > > > '-' '-'
> > > > | |
> > > > | |
> > > > === ===
> > > > GND GND
>
> > > I've done plenty of scheming about how to do it with discretes. But
> > > like you said, I'd still want to use a chip in the end, to get matched
> > > transistors. Pairs and arrays, I see ony surface mount, including
> > > zetex.
> > > If I have to go that way, might as well use the ZXCT1009F in SOT-23
> > > with pins 1.9 mm apart according to the diagram. Almost a tenth of an
> > > inch, could probably solder it right onto the pads of a perfboard, eh?
>
> > Hello,
>
> > When you buy about 10 general purpose PNP transistors from one batch,
> > you will probably find several transistors that are within some mV
> > with same Ic.
>
> Doesn't gain determine the balance in a current mirror? If so, one
> would have to match for gain. I did match for gain last time I
> experimented with current mirrors. I'd like to hear from the experts
> about the need for this.
>
> > When you design the 2 transistor current sensor at low
> > bias current, self heating can be neglected and it saves you from
> > soldering SMD devices like NXP's BCM857. When matching is impossible,
> > you might add a trimmer potentiometer for nulling.
>
> > best regards,
>
> > Wim
> > PA3DJSwww.tetech.nl
>
> About temperature matching. I calculate that one tenth of a degree
> centigrade difference between the transistors in a mirror would add
> about one percent error to the current mirror. I wouldn't want
> temperature vagaries causing any more error than that. I'm wondering
> if you could count on discrete transistors on a board to stay within a
> tenth of a degree to each other. More fodder for the experts.

Hello,

For such circuits matching on Vbe with constant collector current is
sufficient. I normally do it by connecting B to C, bias at required
current and measure the voltage across the diode. Of course for high
volume applications I use a matched pair.

When 1% additional tolerance is unacceptable, you also should evaluate
all other components. I think of current sensing resistor, other
resistors, voltage variatons, offsets in control loop etc. Regarding
temperature, put them close together, take some epoxy resin and some
piece of coper/alu, and temperature difference due to environment will
be negligible.

I can hardly imagine that your original application requires that high
accuracy. Last year I designed several current limiting circuits for
hot swap applications and inrush current limiting and less then 5%
accuracy without adjustment and cheap components will be very
difficult.

Best regards,

Wim
PA3DJS
www.tetech.nl
please remove abc from the address.

Author: Franc Zabkar
Date: 20:42 08-04-08

On Tue, 8 Apr 2008 09:40:29 -0700 (PDT), gearhead
<nospam@billburg.com> put finger to keyboard and composed:

>Hi all, I'd like to help out some friends on an antique motorcycle
>forum that have a 6 volt regulator project. One of them built a
>regulator on perfboard and posted the schematic.

>pdf of the circuit:
>http://www.hydra-glide.com/phpBB2/download.php?id=1173

AFAIK, the LM723 requires a minimum supply voltage of 9.5V. The
internal reference zener is 7.15V, typical.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Author: petrus bitbyter
Date: 20:59 08-04-08

"gearhead" <nospam@billburg.com> schreef in bericht
news:7226e6a4-ddd0-4da5-807a-5799069d795d@k13g2000hse.googlegroups.com...
On Apr 8, 1:30 pm, "petrus bitbyter"
<pieterkraltlaatdit...@enditookhccnet.nl> wrote:
> "gearhead" <nos...@billburg.com> schreef in
> berichtnews:e66fa9e8-d621-4ba3-8c47-fc5752b3f045@m36g2000hse.googlegroups.com...
>
>
>
>
>
> > Hi all, I'd like to help out some friends on an antique motorcycle
> > forum that have a 6 volt regulator project. One of them built a
> > regulator on perfboard and posted the schematic. It has a couple of
> > things I'd tweak, but it works.
> > The main challenge: his regulator design doesn't incorporate current
> > limiting. Even the original relay-style mechanical regulators
> > incorporated current limiting, because the generators required it.
> > Somebody on the forum suggested the zxct1009, but it only comes in
> > surface mount which means we can't rejigger the existing perfboard
> > project to include the new chip. It would mean having a custom-
> > printed circuit board, and soldering techniques perhaps a little too
> > demanding for somebody building his first circuit -- which probably
> > describes a lot of the guys on the forum.
> > pdf of the circuit:
> >http://www.hydra-glide.com/phpBB2/download.php?id=1173
> > I've tried to find a through-hole component that fits the bill, but
> > can't seem to come up with anything just right. I saw the micrel
> > MIC5021, but it supposedly operates on 12 volts and up.
> >http://www.micrel.com/_PDF/mic5021.pdf
> > Now, perhaps they make that statement on the datasheet because the
> > chip actually also has a voltage doubler and the high side drive needs
> > that kind of voltage to turn on a mosfet, and it's possible the chip
> > itself will actually run on a much lower voltage. But the datasheet
> > doesn't say anything to this effect. Has anybody used the MIC5021 and
> > know if it might actually turn on at say 5 volts or perhaps know of
> > any other through hole chips for current sensing?
>
> That Micrel chip is not a current sensor, it is a mosfet driver. Looking
> for
> a highside current sensor, try the MAX4374. A ZXCT1008 or ZXCT1009 may be
> even better. But I doubt you to need that special (and expensive) chips.
>
> Can't be sure what current you want to limit, but usually the field
> current
> is limited to limit the output voltage of the generator. Which in turn
> prevents the battery from being overloaded. This is exactly what the
> circuit
> of your schematic is supposed to do. Just use R1 to set the correct
> voltage.
> For a 6V lead-accid battery this will be about 6,9V. So even for fully
> loaded battery the voltage should never exceed that value. You may have to
> take some voltage loss accross D6 into account which is about 0.2V for
> this
> particular diode.
>
> petrus bitbyter- Hide quoted text -
>
> - Show quoted text -

| Don't say the micrel chip is not a current sensor. It does current
| sensing.
| And current limiting is for the generator, not the battery.

Hmm... Did you check the high-side current sensors I mentioned? As you know
the datasheet of the mic5021 can you explain how you get a signal from it
that is proportional to the measured current? I don't see it, but I like to
learn.

I am not aware of an automotive generator with a current limiter other then
the fields. Normaly the generator is big enough to provide the required
power for the vehicles appliances with a wide margin but yes, you can damage
it by overloading it. Most of the times however you will blow one or more
fuses when you try.

petrus bitbyter

Author: gearhead
Date: 21:41 08-04-08

On Apr 8, 5:59=A0pm, "petrus bitbyter"
<pieterkraltlaatdit...@enditookhccnet.nl> wrote:
> "gearhead" <nos...@billburg.com> schreef in
berichtnews:7226e6a4-ddd0-4da5=
-807a-5799069d795d@k13g2000hse.googlegroups.com...
> On Apr 8, 1:30 pm, "petrus bitbyter"
>
>
>
>
>
> <pieterkraltlaatdit...@enditookhccnet.nl> wrote:
> > "gearhead" <nos...@billburg.com> schreef in
> > berichtnews:e66fa9e8-d621-4ba3-8c47-fc5752b3f045@m36g2000hse.googlegroup=
s.com...
>
> > > Hi all, I'd like to help out some friends on an antique motorcycle
> > > forum that have a 6 volt regulator project. One of them built a
> > > regulator on perfboard and posted the schematic. It has a couple of
> > > things I'd tweak, but it works.
> > > The main challenge: his regulator design doesn't incorporate current
> > > limiting. Even the original relay-style mechanical regulators
> > > incorporated current limiting, because the generators required it.
> > > Somebody on the forum suggested the zxct1009, but it only comes in
> > > surface mount which means we can't rejigger the existing perfboard
> > > project to include the new chip. It would mean having a custom-
> > > printed circuit board, and soldering techniques perhaps a little too
> > > demanding for somebody building his first circuit -- which probably
> > > describes a lot of the guys on the forum.
> > > pdf of the circuit:
> > >http://www.hydra-glide.com/phpBB2/download.php?id=3D1173
> > > I've tried to find a through-hole component that fits the bill, but
> > > can't seem to come up with anything just right. I saw the micrel
> > > MIC5021, but it supposedly operates on 12 volts and up.
> > >http://www.micrel.com/_PDF/mic5021.pdf
> > > Now, perhaps they make that statement on the datasheet because the
> > > chip actually also has a voltage doubler and the high side drive needs=

> > > that kind of voltage to turn on a mosfet, and it's possible the chip
> > > itself will actually run on a much lower voltage. But the datasheet
> > > doesn't say anything to this effect. Has anybody used the MIC5021 and
> > > know if it might actually turn on at say 5 volts or perhaps know of
> > > any other through hole chips for current sensing?
>
> > That Micrel chip is not a current sensor, it is a mosfet driver. Looking=

> > for
> > a highside current sensor, try the MAX4374. A ZXCT1008 or ZXCT1009 may b=
e
> > even better. But I doubt you to need that special (and expensive) chips.=

>
> > Can't be sure what current you want to limit, but usually the field
> > current
> > is limited to limit the output voltage of the generator. Which in turn
> > prevents the battery from being overloaded. This is exactly what the
> > circuit
> > of your schematic is supposed to do. Just use R1 to set the correct
> > voltage.
> > For a 6V lead-accid battery this will be about 6,9V. So even for fully
> > loaded battery the voltage should never exceed that value. You may have =
to
> > take some voltage loss accross D6 into account which is about 0.2V for
> > this
> > particular diode.
>
> > petrus bitbyter- Hide quoted text -
>
> > - Show quoted text -
>
> | Don't say the micrel chip is not a current sensor. =A0It does current
> | sensing.
> | And current limiting is for the generator, not the battery.
>
> Hmm... Did you check the high-side current sensors I mentioned? As you kno=
w
> the datasheet of the mic5021 can you explain how you get a signal from it
> that is proportional to the measured current? I don't see it, but I like t=
o
> learn.

The MIC5021 does not put out a proportional signal, it trips at 50mV.
Yes, maybe it would make the lights flicker if it were to toggle on
and off too slowly. And I looked at the sensors you mentioned, okay?
>
> I am not aware of an automotive generator with a current limiter other the=
n
> the fields. Normaly the generator is big enough to provide the required
> power for the vehicles appliances with a wide margin but yes, you can dama=
ge
> it by overloading it. Most of the times however you will blow one or more
> fuses when you try.
>
> petrus bitbyter- Hide quoted text -
>
> - Show quoted text -

You need to know, this isn't an alernator. Are you familiar with the
old-fashioned generators with the long, skinny armatures with
segmented commutators? They are different from modern alternators in
that they will burn themselves up if you overload them.
Is English a second language for you?

Author: gearhead
Date: 21:55 08-04-08

On Apr 8, 3:53=A0pm, Wimpie <wimabc...@tetech.nl> wrote:
> On 8 abr, 23:32, gearhead <nos...@billburg.com> wrote:
>
>
>
>
>
> > On Apr 8, 2:13 pm, Wimpie <wimabc...@tetech.nl> wrote:
>
> > > On 8 abr, 22:34, gearhead <nos...@billburg.com> wrote:
>
> > > > On Apr 8, 10:03 am, Tim Wescott <t...@seemywebsite.com> wrote:
>
> > > > > gearhead wrote:
> > > > > > Hi all, I'd like to help out some friends on an antique
motorcyc=
le
> > > > > > forum that have a 6 volt regulator project. =A0One of them
built=
a
> > > > > > regulator on perfboard and posted the schematic. =A0It has
a cou=
ple of
> > > > > > things I'd tweak, but it works.
> > > > > > The main challenge: =A0his regulator design doesn't
incorporate =
current
> > > > > > limiting. =A0Even the original relay-style mechanical
regulators=

> > > > > > incorporated current limiting, because the generators
required i=
t.
> > > > > > Somebody on the forum suggested the zxct1009, but it only
comes =
in
> > > > > > surface mount which means we can't rejigger the existing
perfboa=
rd
> > > > > > project to include the new chip. =A0It would mean having a
custo=
m-
> > > > > > printed circuit board, and soldering techniques perhaps a
little=
too
> > > > > > demanding for somebody building his first circuit -- which
proba=
bly
> > > > > > describes a lot of the guys on the forum.
> > > > > > pdf of the circuit:
> > > > > >http://www.hydra-glide.com/phpBB2/download.php?id=3D1173
> > > > > > I've tried to find a through-hole component that fits the
bill, =
but
> > > > > > can't seem to come up with anything just right. =A0I saw
the mic=
rel
> > > > > > MIC5021, but it supposedly operates on 12 volts and up.
> > > > > >http://www.micrel.com/_PDF/mic5021.pdf
> > > > > > Now, perhaps they make that statement on the datasheet
because t=
he
> > > > > > chip actually also has a voltage doubler and the high side
drive=
needs
> > > > > > that kind of voltage to turn on a mosfet, and it's
possible the =
chip
> > > > > > itself will actually run on a much lower voltage. =A0But
the dat=
asheet
> > > > > > doesn't say anything to this effect. =A0Has anybody used
the MIC=
5021 and
> > > > > > know if it might actually turn on at say 5 volts or
perhaps know=
of
> > > > > > any other through hole chips for current sensing?
>
> > > > > This is just a suggestion, but consider the circuit below.
=A0If t=
he
> > > > > transistors are well matched Vchg should come pretty close to
Vgen=
/10 +
> > > > > 47 * 0.02 * Ibatt -- and you can jigger your component values
arou=
nd to
> > > > > change the numbers. =A0You'll _probably_ be able to make this
work=
OK with
> > > > > any two unmatched (but like part-number) PNP transistors, like
2N3=
904's,
> > > > > but you'd do better to get a matched pair (DigiKey has some
Zetex =
parts
> > > > > that would do, if there are any through-hole ones).
>
> > > > > Try this out with SPICE before you run with it: I just threw it
do=
wn off
> > > > > the top of my head, it's not exactly like anything I've done
befor=
e nor
> > > > > is it tested at all.
>
> > > > > =A0 =A0 =A0 Vgen =A0 =A0 =A0 =A0___ =A0 =A0 =A0 =A0Vbatt
> > > > > =A0 =A0 =A0 =A0o-----o---|___|---o-----o
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 | =A0
----->
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 0.02 =A0 =A0| =A0 =A0Ibatt
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 .-. =A0 =A0 =A0 =A0 .-.
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 | |100 =A0 =A0 =A0| |100
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 | | =A0 =A0 =A0 =A0 | |
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 '-' =A0 =A0 =A0 =A0 '-'
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 |
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 |
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 >| =A0 =A0 =A0 |<
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0|---o---|
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 /| =A0 | =A0 |\
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 | =A0 =A0 |
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 | =A0 =A0 |
> > > > > =A0 =A0 =A0Vchg =A0 =A0| =A0 =A0 '-----o
> > > > > =A0 =A0 =A0 =A0o-----o =A0 =A0 =A0 =A0 =A0 |
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 |
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 .-. =A0 =A0 =A0 =A0 .-.
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 | |4.7K =A0 =A0 | |47K
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 | | =A0 =A0 =A0 =A0 | |
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 '-' =A0 =A0 =A0 =A0 '-'
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 |
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 |
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 =3D=3D=3D =A0 =A0 =A0 =A0 =3D=3D=3D
> > > > > =A0 =A0 =A0 =A0 =A0 =A0 GND =A0 =A0 =A0 =A0 GND
>
> > > > I've done plenty of scheming about how to do it with discretes.
=A0B=
ut
> > > > like you said, I'd still want to use a chip in the end, to get
match=
ed
> > > > transistors. =A0Pairs and arrays, I see ony surface mount,
including=

> > > > zetex.
> > > > If I have to go that way, might as well use the ZXCT1009F in SOT-23
> > > > with pins 1.9 mm apart according to the diagram. =A0Almost a tenth
o=
f an
> > > > inch, could probably solder it right onto the pads of a perfboard,
e=
h?
>
> > > Hello,
>
> > > When you buy about 10 general purpose PNP transistors from one batch,
> > > you will probably find several transistors that are within some mV
> > > with same Ic.
>
> > Doesn't gain determine the balance in a current mirror? =A0If so, one
> > would have to match for gain. =A0I did match for gain last time I
> > experimented with current mirrors. =A0I'd like to hear from the experts
> > about the need for this.
>
> > > When you design the 2 transistor current sensor at low
> > > bias current, self heating can be neglected and it saves you from
> > > soldering SMD devices like NXP's BCM857. =A0When matching is impossibl=
e,
> > > you might add a trimmer potentiometer for nulling.
>
> > > best regards,
>
> > > Wim
> > > PA3DJSwww.tetech.nl
>
> > About temperature matching. =A0I calculate that one tenth of a =A0degree=

> > centigrade difference between the transistors in a mirror would add
> > about one percent error to the current mirror. =A0I wouldn't want
> > temperature vagaries causing any more error than that. =A0I'm wondering
> > if you could count on discrete transistors on a board to stay within a
> > tenth of a degree to each other. =A0More fodder for the experts.
>
> Hello,
>
> For such circuits matching on Vbe with constant collector current is
> sufficient. I normally do it by connecting B to C, bias at required
> current and measure the voltage across the diode. =A0Of course for high
> volume applications I use a matched pair.
>
> When 1% additional tolerance is unacceptable, you also should evaluate
> all other components. I think of current sensing =A0resistor, other
> resistors, voltage variatons, offsets in control loop etc. Regarding
> temperature, put them close together, take some epoxy resin and some
> piece of coper/alu, and temperature difference due to environment will
> be negligible.
>
> I can hardly imagine that your original application requires that high
> accuracy. =A0 Last year I designed several current limiting circuits for
> hot swap applications and inrush current limiting and less then 5%
> accuracy without adjustment and cheap components will be very
> difficult.
>
> Best regards,
>
> Wim
> PA3DJSwww.tetech.nl
> please remove abc from the address.- Hide quoted text -
>
> - Show quoted text -

My first dog was named Wimpie.
And there was a Wimpie character in the old Popeye comic that used to
say,
"I will gladly pay you Thursday for a hamburger today!"
Ah, Saturday mornings in front of the TV.

Thanks for the tip about testing Vbe, it makes sense. I guess putting
a bunch of diode-connected transistors in series would really be the
best way, you could go down the line testing voltage and sort them out
right quick.

73 de KF2HI

Author: Scott Seidman
Date: 09:34 09-04-08

gearhead <nospam@billburg.com> wrote in news:e66fa9e8-d621-4ba3-8c47-
fc5752b3f045@m36g2000hse.googlegroups.com:

> if it might actually turn on at say 5 volts or perhaps know of
> any other through hole chips for current sensing?
>

I'd pick up a surfboard and give up on the thruhole idea.

--
Scott
Reverse name to reply

Author: petrus bitbyter
Date: 14:28 09-04-08

"gearhead" <nospam@billburg.com> schreef in bericht
news:b694b51d-ac34-4e3b-9886-18e95b7ea735@e39g2000hsf.googlegroups.com...
On Apr 8, 5:59 pm, "petrus bitbyter"
<pieterkraltlaatdit...@enditookhccnet.nl> wrote:
> "gearhead" <nos...@billburg.com> schreef in
> berichtnews:7226e6a4-ddd0-4da5-807a-5799069d795d@k13g2000hse.googlegroups.com...
> On Apr 8, 1:30 pm, "petrus bitbyter"
>
>
>
>
>
> <pieterkraltlaatdit...@enditookhccnet.nl> wrote:
> > "gearhead" <nos...@billburg.com> schreef in
> >
berichtnews:e66fa9e8-d621-4ba3-8c47-fc5752b3f045@m36g2000hse.googlegroups.com...
>
> > > Hi all, I'd like to help out some friends on an antique motorcycle
> > > forum that have a 6 volt regulator project. One of them built a
> > > regulator on perfboard and posted the schematic. It has a couple of
> > > things I'd tweak, but it works.
> > > The main challenge: his regulator design doesn't incorporate current
> > > limiting. Even the original relay-style mechanical regulators
> > > incorporated current limiting, because the generators required it.
> > > Somebody on the forum suggested the zxct1009, but it only comes in
> > > surface mount which means we can't rejigger the existing perfboard
> > > project to include the new chip. It would mean having a custom-
> > > printed circuit board, and soldering techniques perhaps a little too
> > > demanding for somebody building his first circuit -- which probably
> > > describes a lot of the guys on the forum.
> > > pdf of the circuit:
> > >http://www.hydra-glide.com/phpBB2/download.php?id=1173
> > > I've tried to find a through-hole component that fits the bill, but
> > > can't seem to come up with anything just right. I saw the micrel
> > > MIC5021, but it supposedly operates on 12 volts and up.
> > >http://www.micrel.com/_PDF/mic5021.pdf
> > > Now, perhaps they make that statement on the datasheet because the
> > > chip actually also has a voltage doubler and the high side drive needs
> > > that kind of voltage to turn on a mosfet, and it's possible the chip
> > > itself will actually run on a much lower voltage. But the datasheet
> > > doesn't say anything to this effect. Has anybody used the MIC5021 and
> > > know if it might actually turn on at say 5 volts or perhaps know of
> > > any other through hole chips for current sensing?
>
> > That Micrel chip is not a current sensor, it is a mosfet driver. Looking
> > for
> > a highside current sensor, try the MAX4374. A ZXCT1008 or ZXCT1009 may
> > be
> > even better. But I doubt you to need that special (and expensive) chips.
>
> > Can't be sure what current you want to limit, but usually the field
> > current
> > is limited to limit the output voltage of the generator. Which in turn
> > prevents the battery from being overloaded. This is exactly what the
> > circuit
> > of your schematic is supposed to do. Just use R1 to set the correct
> > voltage.
> > For a 6V lead-accid battery this will be about 6,9V. So even for fully
> > loaded battery the voltage should never exceed that value. You may have
> > to
> > take some voltage loss accross D6 into account which is about 0.2V for
> > this
> > particular diode.
>
> > petrus bitbyter- Hide quoted text -
>
> > - Show quoted text -
>
> | Don't say the micrel chip is not a current sensor. It does current
> | sensing.
> | And current limiting is for the generator, not the battery.
>
> Hmm... Did you check the high-side current sensors I mentioned? As you
> know
> the datasheet of the mic5021 can you explain how you get a signal from it
> that is proportional to the measured current? I don't see it, but I like
> to
> learn.
|
| The MIC5021 does not put out a proportional signal, it trips at 50mV.
| Yes, maybe it would make the lights flicker if it were to toggle on
| and off too slowly. And I looked at the sensors you mentioned, okay?
>
> I am not aware of an automotive generator with a current limiter other
> then
> the fields. Normaly the generator is big enough to provide the required
> power for the vehicles appliances with a wide margin but yes, you can
> damage
> it by overloading it. Most of the times however you will blow one or more
> fuses when you try.
>
> petrus bitbyter- Hide quoted text -
>
> - Show quoted text -
|
| You need to know, this isn't an alernator. Are you familiar with the
| old-fashioned generators with the long, skinny armatures with
| segmented commutators? They are different from modern alternators in
| that they will burn themselves up if you overload them.
| Is English a second language for you?

I remember those old things and the electromecanical circuits that
controlled them, though I never got into their inner workings. So I do not
know about current control and how it was done.

English is not my native tongue.

Consider a ZDX1009. It is SMD but large enough to be mounted on perf board.
The datasheet shows the internal schematic which is very simple so you can
also build it using discretes. You have to use matched transistors as others
stated already.

petrus bitbyter

Author: gearhead
Date: 19:09 09-04-08

> > > > Hi all, I'd like to help out some friends on an antique motorcycle
> > > > forum that have a 6 volt regulator project. One of them built a
> > > > regulator on perfboard and posted the schematic. It has a couple of
> > > > things I'd tweak, but it works.
> > > > The main challenge: his regulator design doesn't incorporate current
> > > > limiting. Even the original relay-style mechanical regulators
> > > > incorporated current limiting, because the generators required it.

(snip)
>
> I remember those old things and the electromecanical circuits that
> controlled them, though I never got into their inner workings. So I do not
> know about current control and how it was done.
>
> English is not my native tongue.
>
> Consider a ZDX1009. It is SMD but large enough to be mounted on perf board.
> The datasheet shows the internal schematic which is very simple so you can
> also build it using discretes. You have to use matched transistors as others
> stated already.
>
> petrus bitbyter

You mean the ZDS1009, petrus.
Check out that circuit in the datasheet -- if it doesn't leak, it
won't turn on.
The circuit below shouldn't have any problem starting up.
Below Ilimit, the collector output will not source any current. Just
as load current passes Ilimit the output collector should start
sourcing a small current. I can use this collector current in a
feedback loop with the voltage regulator and make the load current
settle at Ilimit.

V+----+-----Rs-------+-----+---load
| | |
Re | |
| | |
| | |
\ PN2907 / |
>| x2 |< |
|---+----| |
/| | |\ |
/ | \ |
| | | |
+------' | /
| | |<
| ,-------+--|
| | | |
\ | / \
\| | |/ \
|---+----| '---out
/| |\
< PN2222x2 >
| |
'------+-------'
|
current sink
I = 2 Ilimit Rs / Re
|
|
gnd

For example, Isink = 200 uA, Re = 1k, Rs = .01, Ilimit = 10 A
The current mirrors reach an equilibrium at Ilimit, with 100 uA on
each side.
Below Ilimit, the right side of the current mirror pulls up and the
left side pulls down. The output transistor stays turned off.
Above Ilimit, the left side pulls up and the ride side pulls down,
drawing some current from the base of the output transistor.

Whaddya think, it might work?

Author: gearhead
Date: 09:39 10-04-08

On Apr 9, 4:09=A0pm, gearhead <nos...@billburg.com> wrote:
> > > > > Hi all, I'd like to help out some friends on an antique
motorcycle=

> > > > > forum that have a 6 volt regulator project. One of them built a
> > > > > regulator on perfboard and posted the schematic. It has a
couple o=
f
> > > > > things I'd tweak, but it works.
> > > > > The main challenge: his regulator design doesn't incorporate
curre=
nt
> > > > > limiting. Even the original relay-style mechanical regulators
> > > > > incorporated current limiting, because the generators required
it.=

>
> (snip)
>
>
>
> > I remember those old things and the electromecanical circuits that
> > controlled them, though I never got into their inner workings. So I do n=
ot
> > know about current control and how it was done.
>
> > English is not my native tongue.
>
> > Consider a ZDX1009. It is SMD but large enough to be mounted on perf boa=
rd.
> > The datasheet shows the internal schematic which is very simple so you c=
an
> > also build it using discretes. You have to use matched transistors as ot=
hers
> > stated already.
>
> > petrus bitbyter
>
> You mean the ZDS1009, petrus.
> Check out that circuit in the datasheet -- if it doesn't leak, it
> won't turn on.
> The circuit below shouldn't have any problem starting up.
> Below Ilimit, the collector output will not source any current. =A0Just
> as load current passes Ilimit the output collector should start
> sourcing a small current. =A0I can use this collector current in a
> feedback loop with the voltage regulator and make the load current
> settle at Ilimit.
>
> =A0V+----+-----Rs-------+-----+---load
> =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 |
> =A0 =A0 =A0 =A0Re =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A0 |
> =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 |
> =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A0 |
> =A0 =A0 =A0 =A0 \ =A0 PN2907 =A0 / =A0 =A0 =A0|
> =A0 =A0 =A0 =A0 =A0>| =A0 x2 =A0 |< =A0 =A0 =A0 |
> =A0 =A0 =A0 =A0 =A0 |---+----| =A0 =A0 =A0 =A0|
> =A0 =A0 =A0 =A0 =A0/| =A0 | =A0 =A0|\ =A0 =A0 =A0 |
> =A0 =A0 =A0 =A0 / =A0 =A0 | =A0 =A0 =A0\ =A0 =A0 =A0|
> =A0 =A0 =A0 =A0| =A0 =A0 =A0| =A0 =A0 =A0 | =A0 =A0 |
> =A0 =A0 =A0 =A0+------' =A0 =A0 =A0 | =A0 =A0/
> =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0|<
> =A0 =A0 =A0 =A0| =A0 =A0 =A0,-------+--|
> =A0 =A0 =A0 =A0| =A0 =A0 =A0| =A0 =A0 =A0 | =A0|
> =A0 =A0 =A0 =A0 \ =A0 =A0 | =A0 =A0 =A0/ =A0 =A0\
> =A0 =A0 =A0 =A0 =A0\| =A0 | =A0 =A0|/ =A0 =A0 =A0\
> =A0 =A0 =A0 =A0 =A0 |---+----| =A0 =A0 =A0 =A0'---out
> =A0 =A0 =A0 =A0 =A0/| =A0 =A0 =A0 =A0|\
> =A0 =A0 =A0 =A0 < =A0PN2222x2 =A0>
> =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0 =A0 =A0|
> =A0 =A0 =A0 =A0'------+-------'
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 |
> =A0 =A0 =A0 =A0 =A0current sink
> =A0 =A0 =A0I =3D 2 Ilimit Rs / Re
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 |
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 |
> =A0 =A0 =A0 =A0 =A0 =A0 =A0gnd
>
> For example, Isink =3D 200 uA, Re =3D 1k, Rs =3D .01, Ilimit =3D 10 A
> The current mirrors reach an equilibrium at Ilimit, with 100 uA on
> each side.
> Below Ilimit, the right side of the current mirror pulls up and the
> left side pulls down. =A0The output transistor stays turned off.
> Above Ilimit, the left side pulls up and the ride side pulls down,
> drawing some current from the base of the output transistor.
>
Correction: instead of a mirror it needs separate current sinks on
the ground in order to work.

> V+----+-----Rs-------+-----+---load
> | | |
> Re | |
> | | |
> | | |
> \ PN2907 / |
> >| x2 |< |
> |---+----| |
> /| | |\ |
> / | \ |
> | | | |
> +------' | /
> | | |<
> | +--|
> | | |
> | | \
> | | \
> Isink =3D 100uA =3D Isink '---out
> | |
> '------+-------'
> |
> gnd
>
And another transistor on the output for more gain, if necessary.

Author: petrus bitbyter
Date: 18:56 11-04-08

"gearhead" <nospam@billburg.com> schreef in bericht
news:b7436a31-6637-45cf-a2f8-b549a7a91935@c65g2000hsa.googlegroups.com...
On Apr 9, 4:09 pm, gearhead <nos...@billburg.com> wrote:
> > > > > Hi all, I'd like to help out some friends on an antique
motorcycle
> > > > > forum that have a 6 volt regulator project. One of them built a
> > > > > regulator on perfboard and posted the schematic. It has a
couple
> > > > > of
> > > > > things I'd tweak, but it works.
> > > > > The main challenge: his regulator design doesn't incorporate
> > > > > current
> > > > > limiting. Even the original relay-style mechanical regulators
> > > > > incorporated current limiting, because the generators required
it.
>
> (snip)
>
>
>
> > I remember those old things and the electromecanical circuits that
> > controlled them, though I never got into their inner workings. So I do
> > not
> > know about current control and how it was done.
>
> > English is not my native tongue.
>
> > Consider a ZDX1009. It is SMD but large enough to be mounted on perf
> > board.
> > The datasheet shows the internal schematic which is very simple so you
> > can
> > also build it using discretes. You have to use matched transistors as
> > others
> > stated already.
>
> > petrus bitbyter
>
> You mean the ZDS1009, petrus.
> Check out that circuit in the datasheet -- if it doesn't leak, it
> won't turn on.
> The circuit below shouldn't have any problem starting up.
> Below Ilimit, the collector output will not source any current. Just
> as load current passes Ilimit the output collector should start
> sourcing a small current. I can use this collector current in a
> feedback loop with the voltage regulator and make the load current
> settle at Ilimit.
>
> V+----+-----Rs-------+-----+---load
> | | |
> Re | |
> | | |
> | | |
> \ PN2907 / |
> >| x2 |< |
> |---+----| |
> /| | |\ |
> / | \ |
> | | | |
> +------' | /
> | | |<
> | ,-------+--|
> | | | |
> \ | / \
> \| | |/ \
> |---+----| '---out
> /| |\
> < PN2222x2 >
> | |
> '------+-------'
> |
> current sink
> I = 2 Ilimit Rs / Re
> |
> |
> gnd
>
> For example, Isink = 200 uA, Re = 1k, Rs = .01, Ilimit = 10 A
> The current mirrors reach an equilibrium at Ilimit, with 100 uA on
> each side.
> Below Ilimit, the right side of the current mirror pulls up and the
> left side pulls down. The output transistor stays turned off.
> Above Ilimit, the left side pulls up and the ride side pulls down,
> drawing some current from the base of the output transistor.
>
Correction: instead of a mirror it needs separate current sinks on
the ground in order to work.

> V+----+-----Rs-------+-----+---load
> | | |
> Re | |
> | | |
> | | |
> \ PN2907 / |
> >| x2 |< |
> |---+----| |
> /| | |\ |
> / | \ |
> | | | |
> +------' | /
> | | |<
> | +--|
> | | |
> | | \
> | | \
> Isink = 100uA = Isink '---out
> | |
> '------+-------'
> |
> gnd
>
And another transistor on the output for more gain, if necessary.

Yes, I meant the ZDS1009.

I gave a quick glance and I doubt this circuit will work. The way the
outputtransistor is connected will ruin whatever the others might do. For
instance, most of the current through the right current source will come
through the BE-junction of that transistor. So the balancing for the PN2907
will be gone. Besides, you will have to match both current sources which
brings you directly to the original schematic. Sure, it will not start
without leakage. As a matter of fact, that leakage is specified in the
datasheet. All bipolar transistors I met so far, had some leakage. It's
inherent to to physics of the transistor. Once amplified, it will become
serious current which brings the circuit to live. I ever build a current
sensor like that and it wordked though not very accurate. I used no matched
or twins transistors and did not bother to make them thermal connected. At
the time, it was good enough for my application.

petrus bitbyter

Author: NewsGroups
Date: 19:54 11-04-08

"gearhead" <nospam@billburg.com> wrote in message
news:ffa75aed-3fad-437c-8ad6-0d7d9f907b81@m44g2000hsc.googlegroups.com...
On Apr 8, 2:13 pm, Wimpie <wimabc...@tetech.nl> wrote:
> On 8 abr, 22:34, gearhead <nos...@billburg.com> wrote:
>
>
>
>
>
> > On Apr 8, 10:03 am, Tim Wescott <t...@seemywebsite.com> wrote:
>
> > > gearhead wrote:
> > > > Hi all, I'd like to help out some friends on an antique motorcycle
> > > > forum that have a 6 volt regulator project. One of them built a
> > > > regulator on perfboard and posted the schematic. It has a couple of
> > > > things I'd tweak, but it works.
> > > > The main challenge: his regulator design doesn't incorporate current
> > > > limiting. Even the original relay-style mechanical regulators
> > > > incorporated current limiting, because the generators required it.
> > > > Somebody on the forum suggested the zxct1009, but it only comes in
> > > > surface mount which means we can't rejigger the existing perfboard
> > > > project to include the new chip. It would mean having a custom-
> > > > printed circuit board, and soldering techniques perhaps a little too
> > > > demanding for somebody building his first circuit -- which probably
> > > > describes a lot of the guys on the forum.
> > > > pdf of the circuit:
> > > >http://www.hydra-glide.com/phpBB2/download.php?id=1173
> > > > I've tried to find a through-hole component that fits the bill, but
> > > > can't seem to come up with anything just right. I saw the micrel
> > > > MIC5021, but it supposedly operates on 12 volts and up.
> > > >http://www.micrel.com/_PDF/mic5021.pdf
> > > > Now, perhaps they make that statement on the datasheet because the
> > > > chip actually also has a voltage doubler and the high side drive
> > > > needs
> > > > that kind of voltage to turn on a mosfet, and it's possible the chip
> > > > itself will actually run on a much lower voltage. But the datasheet
> > > > doesn't say anything to this effect. Has anybody used the MIC5021
> > > > and
> > > > know if it might actually turn on at say 5 volts or perhaps know of
> > > > any other through hole chips for current sensing?
>
> > > This is just a suggestion, but consider the circuit below. If the
> > > transistors are well matched Vchg should come pretty close to Vgen/10
> > > +
> > > 47 * 0.02 * Ibatt -- and you can jigger your component values around
> > > to
> > > change the numbers. You'll _probably_ be able to make this work OK
> > > with
> > > any two unmatched (but like part-number) PNP transistors, like
> > > 2N3904's,
> > > but you'd do better to get a matched pair (DigiKey has some Zetex
> > > parts