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Sci.Electronics.Basics -> mosfet as switch
There are 29 messages in this thread.
You are currently looking at messages 1 to 20.
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Author: lerameurDate: 18:26 16-08-08
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hi,
I have two 12v batteries which I am hooking up in parallel using a
mechanical switch (via the ground).
I am attempting to swap the mechanical switch for a mosfet so I can
control them from a distance.
I tried to model in pspice but this is harder then I imagine. I tried
it experimentally, but when I hook up a iRFz44 , the batteries stays
in parallel no matter the voltage in the base. anyone has an idea to
overcome this.
B
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Author: JamieDate: 19:34 16-08-08
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lerameur wrote:
> hi,
>
> I have two 12v batteries which I am hooking up in parallel using a
> mechanical switch (via the ground).
> I am attempting to swap the mechanical switch for a mosfet so I can
> control them from a distance.
> I tried to model in pspice but this is harder then I imagine. I tried
> it experimentally, but when I hook up a iRFz44 , the batteries stays
> in parallel no matter the voltage in the base. anyone has an idea to
> overcome this.
>
> B
If you can't show the circuit then please try to describe its
connections..
My guess is that you're using it incorrectly!.
This Mosfet has a body diode in it, which means if you apply
+ voltage on the source, it'll be there at the drain. And the
Gate is a voltage control device not a current device as you are using
in terms of (BASE). You should at least have a pull down R to ground so
that you keep the gate discharged!. IT's a very high Z input which can
maintain a charge. You also can damage it.
Since this component is a N channel device, you need to pull the
(-) terminal of the battery to common via the Drain connection of
the NMos and the Source goes to common..
The Gate will be switched on via what ever voltage needed.
I didn't look at all of the spec's
http://webpages.charter.net/jamie_5";
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Author: lerameurDate: 21:03 16-08-08
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On Aug 16, 7:34 pm, Jamie
<jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
> lerameur wrote:
> > hi,
>
> > I have two 12v batteries which I am hooking up in parallel using a
> > mechanical switch (via the ground).
> > I am attempting to swap the mechanical switch for a mosfet so I can
> > control them from a distance.
> > I tried to model in pspice but this is harder then I imagine. I tried
> > it experimentally, but when I hook up a iRFz44 , the batteries stays
> > in parallel no matter the voltage in the base. anyone has an idea to
> > overcome this.
>
> > B
>
> If you can't show the circuit then please try to describe its
> connections..
> My guess is that you're using it incorrectly!.
>
> This Mosfet has a body diode in it, which means if you apply
> + voltage on the source, it'll be there at the drain. And the
> Gate is a voltage control device not a current device as you are using
> in terms of (BASE). You should at least have a pull down R to ground so
> that you keep the gate discharged!. IT's a very high Z input which can
> maintain a charge. You also can damage it.
>
> Since this component is a N channel device, you need to pull the
> (-) terminal of the battery to common via the Drain connection of
> the NMos and the Source goes to common..
>
> The Gate will be switched on via what ever voltage needed.
> I didn't look at all of the spec's
>
> http://webpages.charter.net/jamie_5";
the circuit is really simple.
connection the ground of two batteries, the positives are not attached
to anything.
yes I could use an alligator clip and hook up the two grounds
together. But I would like to use a semiconductor. I would need some
sort of mosfet but when the gate is activated, it can let current flow
in both direction, is there anything on the market that can do this?
B
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Author: lerameurDate: 21:09 16-08-08
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On Aug 16, 9:03 pm, lerameur <leram...@yahoo.com> wrote:
> On Aug 16, 7:34 pm, Jamie
>
>
>
> <jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
> > lerameur wrote:
> > > hi,
>
> > > I have two 12v batteries which I am hooking up in parallel using a
> > > mechanical switch (via the ground).
> > > I am attempting to swap the mechanical switch for a mosfet so I can
> > > control them from a distance.
> > > I tried to model in pspice but this is harder then I imagine. I tried
> > > it experimentally, but when I hook up a iRFz44 , the batteries stays
> > > in parallel no matter the voltage in the base. anyone has an idea to
> > > overcome this.
>
> > > B
>
> > If you can't show the circuit then please try to describe its
> > connections..
> > My guess is that you're using it incorrectly!.
>
> > This Mosfet has a body diode in it, which means if you apply
> > + voltage on the source, it'll be there at the drain. And the
> > Gate is a voltage control device not a current device as you are using
> > in terms of (BASE). You should at least have a pull down R to ground so
> > that you keep the gate discharged!. IT's a very high Z input which can
> > maintain a charge. You also can damage it.
>
> > Since this component is a N channel device, you need to pull the
> > (-) terminal of the battery to common via the Drain connection of
> > the NMos and the Source goes to common..
>
> > The Gate will be switched on via what ever voltage needed.
> > I didn't look at all of the spec's
>
> >http://webpages.charter.net/jamie_5";
>
> the circuit is really simple.
> connection the ground of two batteries, the positives are not attached
> to anything.
> yes I could use an alligator clip and hook up the two grounds
> together. But I would like to use a semiconductor. I would need some
> sort of mosfet but when the gate is activated, it can let current flow
> in both direction, is there anything on the market that can do this?
>
> B
I think it is called a UJT, just need to find one in pspice...
B
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Author: JamieDate: 22:34 16-08-08
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lerameur wrote:
> On Aug 16, 7:34 pm, Jamie
> <jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
>
>>lerameur wrote:
>>
>>>hi,
>>
>>>I have two 12v batteries which I am hooking up in parallel using a
>>>mechanical switch (via the ground).
>>>I am attempting to swap the mechanical switch for a mosfet so I can
>>>control them from a distance.
>>>I tried to model in pspice but this is harder then I imagine. I tried
>>>it experimentally, but when I hook up a iRFz44 , the batteries stays
>>>in parallel no matter the voltage in the base. anyone has an idea to
>>>overcome this.
>>
>>>B
>>
>> If you can't show the circuit then please try to describe its
>>connections..
>> My guess is that you're using it incorrectly!.
>>
>> This Mosfet has a body diode in it, which means if you apply
>> + voltage on the source, it'll be there at the drain. And the
>>Gate is a voltage control device not a current device as you are using
>>in terms of (BASE). You should at least have a pull down R to ground so
>>that you keep the gate discharged!. IT's a very high Z input which can
>>maintain a charge. You also can damage it.
>>
>> Since this component is a N channel device, you need to pull the
>>(-) terminal of the battery to common via the Drain connection of
>>the NMos and the Source goes to common..
>>
>> The Gate will be switched on via what ever voltage needed.
>> I didn't look at all of the spec's
>>
>>http://webpages.charter.net/jamie_5";
>
>
> the circuit is really simple.
> connection the ground of two batteries, the positives are not attached
> to anything.
> yes I could use an alligator clip and hook up the two grounds
> together. But I would like to use a semiconductor. I would need some
> sort of mosfet but when the gate is activated, it can let current flow
> in both direction, is there anything on the market that can do this?
>
> B
Are you saying you want to put these batteries in series ?
I think at this point you maybe better off using a relay..
http://webpages.charter.net/jamie_5";
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Author: lerameurDate: 06:36 17-08-08
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On Aug 16, 10:34 pm, Jamie
<jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
> lerameur wrote:
> > On Aug 16, 7:34 pm, Jamie
> > <jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
>
> >>lerameur wrote:
>
> >>>hi,
>
> >>>I have two 12v batteries which I am hooking up in parallel using a
> >>>mechanical switch (via the ground).
> >>>I am attempting to swap the mechanical switch for a mosfet so I can
> >>>control them from a distance.
> >>>I tried to model in pspice but this is harder then I imagine. I tried
> >>>it experimentally, but when I hook up a iRFz44 , the batteries stays
> >>>in parallel no matter the voltage in the base. anyone has an idea to
> >>>overcome this.
>
> >>>B
>
> >> If you can't show the circuit then please try to describe its
> >>connections..
> >> My guess is that you're using it incorrectly!.
>
> >> This Mosfet has a body diode in it, which means if you apply
> >> + voltage on the source, it'll be there at the drain. And the
> >>Gate is a voltage control device not a current device as you are using
> >>in terms of (BASE). You should at least have a pull down R to ground so
> >>that you keep the gate discharged!. IT's a very high Z input which can
> >>maintain a charge. You also can damage it.
>
> >> Since this component is a N channel device, you need to pull the
> >>(-) terminal of the battery to common via the Drain connection of
> >>the NMos and the Source goes to common..
>
> >> The Gate will be switched on via what ever voltage needed.
> >> I didn't look at all of the spec's
>
> >>http://webpages.charter.net/jamie_5";
>
> > the circuit is really simple.
> > connection the ground of two batteries, the positives are not attached
> > to anything.
> > yes I could use an alligator clip and hook up the two grounds
> > together. But I would like to use a semiconductor. I would need some
> > sort of mosfet but when the gate is activated, it can let current flow
> > in both direction, is there anything on the market that can do this?
>
> > B
>
> Are you saying you want to put these batteries in series ?
>
> I think at this point you maybe better off using a relay..
>
> http://webpages.charter.net/jamie_5";
two grounds together, that would be parallel, But the UJT is taking
too much current just to enable it. The problem is that when I put a
MOsfet with source on one grounds and the drain on the other ground,
the batteries are in parallel. no matter what the gate voltage is...
B
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Author: mikedunnDate: 06:37 17-08-08
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On Aug 17, 5:34=A0am, Jamie
<jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
> lerameur wrote:
> > On Aug 16, 7:34 pm, Jamie
> > <jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
>
> >>lerameur wrote:
>
> >>>hi,
>
> >>>I have two 12v batteries which I am hooking up in parallel using a
> >>>mechanical switch (via the ground).
> >>>I am attempting to swap the mechanical switch for a mosfet so I can
> >>>control them from a distance.
> >>>I tried to model in pspice but this is harder then I imagine. I tried
> >>>it experimentally, but when I hook up a iRFz44 , the batteries stays
> >>>in parallel no matter the voltage in the base. anyone has an idea to
> >>>overcome this.
>
> >>>B
>
> >> =A0If you can't show the circuit then please try to describe its
> >>connections..
> >> =A0 My guess is that you're using it incorrectly!.
>
> >> =A0 This Mosfet has a body diode in it, which means if you apply
> >> =A0+ voltage on the source, it'll be there at the drain. And the
> >>Gate is a voltage control device not a current device as you are using
> >>in terms of (BASE). You should at least have a pull down R to ground so
> >>that you keep the gate discharged!. IT's a very high Z input which can
> >>maintain a charge. You also can damage it.
>
> >> =A0 Since this component is a N channel device, you need to pull the
> >>(-) terminal of the battery to common via the Drain connection of
> >>the NMos and the Source goes to common..
>
> >> =A0 =A0The Gate will be switched on via what ever voltage needed.
> >> =A0I didn't look at all of the spec's
>
> >>http://webpages.charter.net/jamie_5";
>
> > the circuit is really simple.
> > connection the ground of two batteries, the positives are not attached
> > to anything.
> > yes I could use an alligator clip and hook up the two grounds
> > together. But I would like to use a semiconductor. I would need some
> > sort of mosfet but when the gate is activated, it can let current flow
> > in both direction, is there anything on the market that can do this?
>
> > B
>
> Are you saying you want to put these batteries in series ?
>
> =A0 =A0I think at this point you maybe better off using a relay..
>
> http://webpages.charter.net/jamie_5";
Remember Occam's razor.
Don't use a transistor when a switch will do; don't use an IC when a
transistor will do........
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Author: Jasen BettsDate: 08:02 17-08-08
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On 2008-08-17, lerameur <lerameur@yahoo.com> wrote:
> On Aug 16, 7:34 pm, Jamie
><jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
>> lerameur wrote:
>> > hi,
>>
>> > I have two 12v batteries which I am hooking up in parallel using a
>> > mechanical switch (via the ground).
>> > I am attempting to swap the mechanical switch for a mosfet so I can
>> > control them from a distance.
>> > I tried to model in pspice but this is harder then I imagine. I tried
>> > it experimentally, but when I hook up a iRFz44 , the batteries stays
>> > in parallel no matter the voltage in the base. anyone has an idea to
>> > overcome this.
>>
>
> the circuit is really simple.
> connection the ground of two batteries, the positives are not attached
> to anything.
Batteries connected like that will do nothing, more details would help.
> yes I could use an alligator clip and hook up the two grounds
> together. But I would like to use a semiconductor. I would need some
> sort of mosfet but when the gate is activated, it can let current flow
> in both direction, is there anything on the market that can do this?
MOSFETs will do that they just have that annoying body diode that
makes them always conduct (like a diode) in the backwards direction.
you may be able to escape this problem by connecting two back-to
back.
connect the gates together and the drains, then connect the sources
to the batteries and the gates to your control signal.
Bye.
Jasen
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Author: Phil AllisonDate: 08:09 17-08-08
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"lerameur"
** = primate relative of the lemur
> But the UJT is taking...
** Huh ?????????
UJT = what ?
Uni - junction transistor ???
The term you want is " BJT " - fuckwit.
..... Phil
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Author: John FieldsDate: 10:49 18-08-08
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On Sun, 17 Aug 2008 03:36:20 -0700 (PDT), lerameur
<lerameur@yahoo.com> wrote:
>On Aug 16, 10:34 pm, Jamie
><jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
>> lerameur wrote:
>> > On Aug 16, 7:34 pm, Jamie
>> > <jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
>>
>> >>lerameur wrote:
>>
>> >>>hi,
>>
>> >>>I have two 12v batteries which I am hooking up in parallel using a
>> >>>mechanical switch (via the ground).
>> >>>I am attempting to swap the mechanical switch for a mosfet so I can
>> >>>control them from a distance.
>> >>>I tried to model in pspice but this is harder then I imagine. I
tried
>> >>>it experimentally, but when I hook up a iRFz44 , the batteries
stays
>> >>>in parallel no matter the voltage in the base. anyone has an idea
to
>> >>>overcome this.
>>
>> >>>B
>>
>> >> If you can't show the circuit then please try to describe its
>> >>connections..
>> >> My guess is that you're using it incorrectly!.
>>
>> >> This Mosfet has a body diode in it, which means if you apply
>> >> + voltage on the source, it'll be there at the drain. And the
>> >>Gate is a voltage control device not a current device as you are using
>> >>in terms of (BASE). You should at least have a pull down R to ground so
>> >>that you keep the gate discharged!. IT's a very high Z input which can
>> >>maintain a charge. You also can damage it.
>>
>> >> Since this component is a N channel device, you need to pull the
>> >>(-) terminal of the battery to common via the Drain connection of
>> >>the NMos and the Source goes to common..
>>
>> >> The Gate will be switched on via what ever voltage needed.
>> >> I didn't look at all of the spec's
>>
>> >>http://webpages.charter.net/jamie_5";
>>
>> > the circuit is really simple.
>> > connection the ground of two batteries, the positives are not attached
>> > to anything.
>> > yes I could use an alligator clip and hook up the two grounds
>> > together. But I would like to use a semiconductor. I would need some
>> > sort of mosfet but when the gate is activated, it can let current flow
>> > in both direction, is there anything on the market that can do this?
>>
>> > B
>>
>> Are you saying you want to put these batteries in series ?
>>
>> I think at this point you maybe better off using a relay..
>>
>> http://webpages.charter.net/jamie_5";
>
>two grounds together, that would be parallel, But the UJT is taking
>too much current just to enable it. The problem is that when I put a
>MOsfet with source on one grounds and the drain on the other ground,
>the batteries are in parallel. no matter what the gate voltage is...
---
Assuming you want to drive some sort of load, this should do it:
Version 4
SHEET 1 1268 944
WIRE -32 48 -352 48
WIRE 144 48 -32 48
WIRE 320 48 144 48
WIRE -352 112 -352 48
WIRE -32 128 -32 48
WIRE 144 128 144 48
WIRE -528 256 -592 256
WIRE -400 256 -528 256
WIRE -192 256 -400 256
WIRE -592 288 -592 256
WIRE 320 288 320 48
WIRE -528 336 -528 256
WIRE -352 336 -352 192
WIRE -192 336 -192 256
WIRE -400 352 -400 256
WIRE -32 448 -32 208
WIRE 144 448 144 208
WIRE -528 496 -528 416
WIRE -400 496 -400 400
WIRE -400 496 -528 496
WIRE -352 496 -352 416
WIRE -192 496 -192 416
WIRE -192 496 -352 496
WIRE -128 496 -192 496
WIRE -96 496 -128 496
WIRE 240 496 208 496
WIRE -128 592 -128 496
WIRE 240 592 240 496
WIRE 240 592 -128 592
WIRE -32 656 -32 544
WIRE 144 656 144 544
WIRE 144 656 -32 656
WIRE 320 656 320 368
WIRE 320 656 144 656
FLAG -592 288 0
SYMBOL voltage -528 432 R180
WINDOW 0 -53 5 Left 0
WINDOW 3 -242 110 Invisible 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value PULSE(0 1 0 1E-6 1E-6 1 2)
SYMBOL sw -352 320 R0
WINDOW 0 32 15 Left 0
WINDOW 3 32 44 Left 0
SYMATTR InstName S2
SYMBOL npn -96 544 M180
SYMATTR InstName Q1
SYMATTR Value 2N2222
SYMBOL voltage -32 112 R0
WINDOW 0 -53 5 Left 0
WINDOW 3 -242 110 Invisible 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 12
SYMBOL res 304 272 R0
SYMATTR InstName R2
SYMATTR Value 24
SYMBOL res -208 320 R0
SYMATTR InstName R1
SYMATTR Value 10k
SYMBOL res -368 96 R0
SYMATTR InstName R3
SYMATTR Value 1k
SYMBOL voltage 144 112 R0
WINDOW 0 -53 5 Left 0
WINDOW 3 -242 110 Invisible 0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V3
SYMATTR Value 12
SYMBOL npn 208 544 R180
SYMATTR InstName Q2
SYMATTR Value 2N2222
TEXT -720 528 Left 0 !.model SW SW(Ron=.01 Roff=10Meg Vt=0.5Vh=0)
TEXT -712 488 Left 0 !.tran 0 10 0
But what are you trying to do?
JF
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Author: lerameurDate: 15:10 18-08-08
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On Aug 18, 10:49 am, John Fields <jfie...@austininstruments.com>
wrote:
> On Sun, 17 Aug 2008 03:36:20 -0700 (PDT), lerameur
>
>
>
> <leram...@yahoo.com> wrote:
> >On Aug 16, 10:34 pm, Jamie
> ><jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
> >> lerameur wrote:
> >> > On Aug 16, 7:34 pm, Jamie
> >> > <jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
>
> >> >>lerameur wrote:
>
> >> >>>hi,
>
> >> >>>I have two 12v batteries which I am hooking up in parallel
using a
> >> >>>mechanical switch (via the ground).
> >> >>>I am attempting to swap the mechanical switch for a mosfet so
I can
> >> >>>control them from a distance.
> >> >>>I tried to model in pspice but this is harder then I imagine.
I tried
> >> >>>it experimentally, but when I hook up a iRFz44 , the batteries
stays
> >> >>>in parallel no matter the voltage in the base. anyone has an
idea to
> >> >>>overcome this.
>
> >> >>>B
>
> >> >> If you can't show the circuit then please try to describe its
> >> >>connections..
> >> >> My guess is that you're using it incorrectly!.
>
> >> >> This Mosfet has a body diode in it, which means if you apply
> >> >> + voltage on the source, it'll be there at the drain. And the
> >> >>Gate is a voltage control device not a current device as you are
using
> >> >>in terms of (BASE). You should at least have a pull down R to
ground so
> >> >>that you keep the gate discharged!. IT's a very high Z input which
can
> >> >>maintain a charge. You also can damage it.
>
> >> >> Since this component is a N channel device, you need to pull
the
> >> >>(-) terminal of the battery to common via the Drain connection of
> >> >>the NMos and the Source goes to common..
>
> >> >> The Gate will be switched on via what ever voltage needed.
> >> >> I didn't look at all of the spec's
>
> >> >>http://webpages.charter.net/jamie_5";
>
> >> > the circuit is really simple.
> >> > connection the ground of two batteries, the positives are not
attached
> >> > to anything.
> >> > yes I could use an alligator clip and hook up the two grounds
> >> > together. But I would like to use a semiconductor. I would need some
> >> > sort of mosfet but when the gate is activated, it can let current
flow
> >> > in both direction, is there anything on the market that can do this?
>
> >> > B
>
> >> Are you saying you want to put these batteries in series ?
>
> >> I think at this point you maybe better off using a relay..
>
> >>http://webpages.charter.net/jamie_5";
>
> >two grounds together, that would be parallel, But the UJT is taking
> >too much current just to enable it. The problem is that when I put a
> >MOsfet with source on one grounds and the drain on the other ground,
> >the batteries are in parallel. no matter what the gate voltage is...
>
> ---
> Assuming you want to drive some sort of load, this should do it:
>
> Version 4
> SHEET 1 1268 944
> WIRE -32 48 -352 48
> WIRE 144 48 -32 48
> WIRE 320 48 144 48
> WIRE -352 112 -352 48
> WIRE -32 128 -32 48
> WIRE 144 128 144 48
> WIRE -528 256 -592 256
> WIRE -400 256 -528 256
> WIRE -192 256 -400 256
> WIRE -592 288 -592 256
> WIRE 320 288 320 48
> WIRE -528 336 -528 256
> WIRE -352 336 -352 192
> WIRE -192 336 -192 256
> WIRE -400 352 -400 256
> WIRE -32 448 -32 208
> WIRE 144 448 144 208
> WIRE -528 496 -528 416
> WIRE -400 496 -400 400
> WIRE -400 496 -528 496
> WIRE -352 496 -352 416
> WIRE -192 496 -192 416
> WIRE -192 496 -352 496
> WIRE -128 496 -192 496
> WIRE -96 496 -128 496
> WIRE 240 496 208 496
> WIRE -128 592 -128 496
> WIRE 240 592 240 496
> WIRE 240 592 -128 592
> WIRE -32 656 -32 544
> WIRE 144 656 144 544
> WIRE 144 656 -32 656
> WIRE 320 656 320 368
> WIRE 320 656 144 656
> FLAG -592 288 0
> SYMBOL voltage -528 432 R180
> WINDOW 0 -53 5 Left 0
> WINDOW 3 -242 110 Invisible 0
> WINDOW 123 0 0 Left 0
> WINDOW 39 0 0 Left 0
> SYMATTR InstName V2
> SYMATTR Value PULSE(0 1 0 1E-6 1E-6 1 2)
> SYMBOL sw -352 320 R0
> WINDOW 0 32 15 Left 0
> WINDOW 3 32 44 Left 0
> SYMATTR InstName S2
> SYMBOL npn -96 544 M180
> SYMATTR InstName Q1
> SYMATTR Value 2N2222
> SYMBOL voltage -32 112 R0
> WINDOW 0 -53 5 Left 0
> WINDOW 3 -242 110 Invisible 0
> WINDOW 123 0 0 Left 0
> WINDOW 39 0 0 Left 0
> SYMATTR InstName V1
> SYMATTR Value 12
> SYMBOL res 304 272 R0
> SYMATTR InstName R2
> SYMATTR Value 24
> SYMBOL res -208 320 R0
> SYMATTR InstName R1
> SYMATTR Value 10k
> SYMBOL res -368 96 R0
> SYMATTR InstName R3
> SYMATTR Value 1k
> SYMBOL voltage 144 112 R0
> WINDOW 0 -53 5 Left 0
> WINDOW 3 -242 110 Invisible 0
> WINDOW 123 0 0 Left 0
> WINDOW 39 0 0 Left 0
> SYMATTR InstName V3
> SYMATTR Value 12
> SYMBOL npn 208 544 R180
> SYMATTR InstName Q2
> SYMATTR Value 2N2222
> TEXT -720 528 Left 0 !.model SW SW(Ron=.01 Roff=10Meg Vt=0.5Vh=0)
> TEXT -712 488 Left 0 !.tran 0 10 0
>
> But what are you trying to do?
>
> JF
What I want to do is to be able to fully control by battery bank at a
distance. I have some batteries that are fully charged and others need
to be charged. I would like to switch over a specific battery from one
battery bank to another without moving it. So, in one of the case, I
would want to hook up an extra battery in parallel when in the battery
bank, therefore I need to hook up the positive to the bank positive
and the negative to the bank negative. I am having a bit of problem
hooking up two identical voltage.
B
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Author: John FieldsDate: 16:21 18-08-08
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On Mon, 18 Aug 2008 12:10:26 -0700 (PDT), lerameur
<lerameur@yahoo.com> wrote:
>On Aug 18, 10:49 am, John Fields <jfie...@austininstruments.com>
>wrote:
>> But what are you trying to do?
>>
>> JF
>
>What I want to do is to be able to fully control by battery bank at a
>distance. I have some batteries that are fully charged and others need
>to be charged. I would like to switch over a specific battery from one
>battery bank to another without moving it. So, in one of the case, I
>would want to hook up an extra battery in parallel when in the battery
>bank, therefore I need to hook up the positive to the bank positive
>and the negative to the bank negative. I am having a bit of problem
>hooking up two identical voltage.
>
>B
---
I still don't really understand what you're trying to do.
Can you explain your application in detail?
JF
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On Aug 18, 1:21 pm, John Fields <jfie...@austininstruments.com> wrote:
> On Mon, 18 Aug 2008 12:10:26 -0700 (PDT), lerameur
>
>
>
> <leram...@yahoo.com> wrote:
> >On Aug 18, 10:49 am, John Fields <jfie...@austininstruments.com>
> >wrote:
> >> But what are you trying to do?
>
> >> JF
>
> >What I want to do is to be able to fully control by battery bank at a
> >distance. I have some batteries that are fully charged and others need
> >to be charged. I would like to switch over a specific battery from one
> >battery bank to another without moving it. So, in one of the case, I
> >would want to hook up an extra battery in parallel when in the battery
> >bank, therefore I need to hook up the positive to the bank positive
> >and the negative to the bank negative. I am having a bit of problem
> >hooking up two identical voltage.
>
> >B
>
> ---
> I still don't really understand what you're trying to do.
>
> Can you explain your application in detail?
>
> JF
Trying not to get blown up by his lead-acid battery bank? ;-)
Michael
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Author: lerameurDate: 17:24 18-08-08
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On Aug 18, 4:21 pm, John Fields <jfie...@austininstruments.com> wrote:
> On Mon, 18 Aug 2008 12:10:26 -0700 (PDT), lerameur
>
>
>
> <leram...@yahoo.com> wrote:
> >On Aug 18, 10:49 am, John Fields <jfie...@austininstruments.com>
> >wrote:
> >> But what are you trying to do?
>
> >> JF
>
> >What I want to do is to be able to fully control by battery bank at a
> >distance. I have some batteries that are fully charged and others need
> >to be charged. I would like to switch over a specific battery from one
> >battery bank to another without moving it. So, in one of the case, I
> >would want to hook up an extra battery in parallel when in the battery
> >bank, therefore I need to hook up the positive to the bank positive
> >and the negative to the bank negative. I am having a bit of problem
> >hooking up two identical voltage.
>
> >B
>
> ---
> I still don't really understand what you're trying to do.
>
> Can you explain your application in detail?
>
> JF
I posted the circuit on the following link:
http://www3.sympatico.ca/lerameur/batteries/multiple_grounds.jpg
The idea is to disable M1 so only battery V2 V3 and V4 are used.
B
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Author: HammyDate: 18:15 18-08-08
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On Sat, 16 Aug 2008 15:26:36 -0700 (PDT), lerameur
<lerameur@yahoo.com> wrote:
>hi,
>
>I have two 12v batteries which I am hooking up in parallel using a
>mechanical switch (via the ground).
>I am attempting to swap the mechanical switch for a mosfet so I can
>control them from a distance.
>I tried to model in pspice but this is harder then I imagine. I tried
>it experimentally, but when I hook up a iRFz44 , the batteries stays
>in parallel no matter the voltage in the base. anyone has an idea to
>overcome this.
>
>B
I'm not sure I fully understand what your trying to do,but if your
switching between batteries you should use a bidirectional switch.
This stops body diode conduction of the FET.
http://i33.tinypic.com/ddm9ap.png
I dont know your load but here is a pretty good PFET if it's beefy
enough for you.
http://www.fairchildsemi.com/ds/FD%2FFDD4141.pdf
You can get ten at Digikey for a little over Ten bucks.You will also
need a mosfet driver.
Here some reading for mosfets. 100 page PDF from fairchild .
http://huqixin.blog.dianyuan.com/u/61/1199250649.pdf
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Author: HammyDate: 18:53 18-08-08
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On Mon, 18 Aug 2008 22:15:22 GMT, Hammy <spamme@hotmail.com> wrote:
>On Sat, 16 Aug 2008 15:26:36 -0700 (PDT), lerameur
><lerameur@yahoo.com> wrote:
>
>>hi,
>>
>>I have two 12v batteries which I am hooking up in parallel using a
>>mechanical switch (via the ground).
>>I am attempting to swap the mechanical switch for a mosfet so I can
>>control them from a distance.
>>I tried to model in pspice but this is harder then I imagine. I tried
>>it experimentally, but when I hook up a iRFz44 , the batteries stays
>>in parallel no matter the voltage in the base. anyone has an idea to
>>overcome this.
>>
>>B
>
>I'm not sure I fully understand what your trying to do,but if your
>switching between batteries you should use a bidirectional switch.
>This stops body diode conduction of the FET.
>
>http://i33.tinypic.com/ddm9ap.png
Made a mistake in my drawing.
Those two mosfets should be connected source to source.
>I dont know your load but here is a pretty good PFET if it's beefy
>enough for you.
>
>http://www.fairchildsemi.com/ds/FD%2FFDD4141.pdf
>
>You can get ten at Digikey for a little over Ten bucks.You will also
>need a mosfet driver.
>
>Here some reading for mosfets. 100 page PDF from fairchild .
>
>http://huqixin.blog.dianyuan.com/u/61/1199250649.pdf
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Author: John PopelishDate: 20:09 18-08-08
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lerameur wrote:
> I posted the circuit on the following link:
> http://www3.sympatico.ca/lerameur/batteries/multiple_grounds.jpg
>
> The idea is to disable M1 so only battery V2 V3 and V4 are used.
The problem with that design is the internal diode that
parallels each MOSFET. For one direction of current, each
MOSFET will conduct through that diode, even if the gate is
reverse biased. Even if you reconfigure this parallel
battery arrangement to have each battery negative connect to
a single common node node (instead of a ladder structure)
you still have to account for both battery charge and
discharge current (if the batteries will be charged in
place). That requires a pair of MOSFETs in series, an
N-channel and a P-channel, so that each one blocks for the
other when its internal diode is forward biased.
The you have to get the gate biasing right.
--
Regards,
John Popelish
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Author: lerameurDate: 21:53 18-08-08
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On Aug 18, 8:09 pm, John Popelish <jpopel...@rica.net> wrote:
> lerameur wrote:
> > I posted the circuit on the following link:
> >http://www3.sympatico.ca/lerameur/batteries/multiple_grounds.jpg
>
> > The idea is to disable M1 so only battery V2 V3 and V4 are used.
>
> The problem with that design is the internal diode that
> parallels each MOSFET. For one direction of current, each
> MOSFET will conduct through that diode, even if the gate is
> reverse biased. Even if you reconfigure this parallel
> battery arrangement to have each battery negative connect to
> a single common node node (instead of a ladder structure)
> you still have to account for both battery charge and
> discharge current (if the batteries will be charged in
> place). That requires a pair of MOSFETs in series, an
> N-channel and a P-channel, so that each one blocks for the
> other when its internal diode is forward biased.
>
> The you have to get the gate biasing right.
>
> --
> Regards,
>
> John Popelish
I have been reading this pdf from above
http://www.fairchildsemi.com/ds/FD%2FFDD4141.pdf
what is confusing is on page 10 (4-10)
THEY PUT 2 N-CHANNEL MOSFET back to back, with an arrow with current
pointing to both direction, this seems wrong, I thought current can
only flow in one direction, is this pdf right?
B
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Author: lerameurDate: 21:57 18-08-08
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On Aug 18, 8:09 pm, John Popelish <jpopel...@rica.net> wrote:
> lerameur wrote:
> > I posted the circuit on the following link:
> >http://www3.sympatico.ca/lerameur/batteries/multiple_grounds.jpg
>
> > The idea is to disable M1 so only battery V2 V3 and V4 are used.
>
> The problem with that design is the internal diode that
> parallels each MOSFET. For one direction of current, each
> MOSFET will conduct through that diode, even if the gate is
> reverse biased. Even if you reconfigure this parallel
> battery arrangement to have each battery negative connect to
> a single common node node (instead of a ladder structure)
> you still have to account for both battery charge and
> discharge current (if the batteries will be charged in
> place). That requires a pair of MOSFETs in series, an
> N-channel and a P-channel, so that each one blocks for the
> other when its internal diode is forward biased.
>
> The you have to get the gate biasing right.
>
> --
> Regards,
>
> John Popelish
I have been reading this pdf from above
http://www.fairchildsemi.com/ds/FD%2FFDD4141.pdf
what is confusing is on page 10 (4-10)
THEY PUT 2 N-CHANNEL MOSFET back to back, with an arrow with current
pointing to both direction, this seems wrong, I thought current can
only flow in one direction, is this pdf right?
B
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Author: John PopelishDate: 22:08 18-08-08
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lerameur wrote:
> On Aug 18, 8:09 pm, John Popelish <jpopel...@rica.net> wrote:
>> lerameur wrote:
>>> I posted the circuit on the following link:
>>> http://www3.sympatico.ca/lerameur/batteries/multiple_grounds.jpg
>>> The idea is to disable M1 so only battery V2 V3 and V4 are used.
>> The problem with that design is the internal diode that
>> parallels each MOSFET. For one direction of current, each
>> MOSFET will conduct through that diode, even if the gate is
>> reverse biased. Even if you reconfigure this parallel
>> battery arrangement to have each battery negative connect to
>> a single common node node (instead of a ladder structure)
>> you still have to account for both battery charge and
>> discharge current (if the batteries will be charged in
>> place). That requires a pair of MOSFETs in series, an
>> N-channel and a P-channel, so that each one blocks for the
>> other when its internal diode is forward biased.
>>
>> The you have to get the gate biasing right.
> I have been reading this pdf from above
> http://www.fairchildsemi.com/ds/FD%2FFDD4141.pdf
> what is confusing is on page 10 (4-10)
> THEY PUT 2 N-CHANNEL MOSFET back to back, with an arrow with current
> pointing to both direction, this seems wrong, I thought current can
> only flow in one direction, is this pdf right?
I am the one who made a mistake. You need two MOSFETs, so
that you can point a body diode each way, so that one or the
other blocks current, regardless of the current direction.
They can both be N-channel, both P-channel, or one P and one
N-channel, as long as the body diodes are pointing both
ways. The choice of type depends on which way the gate
biasing is most convenient.
That the current can go both ways is exactly the problem.
You get conduction through the channel (in either direction)
in parallel with the body diode, but one or the other MOSFET
must have a body diode reverse biased if the pair is to be
an open circuit when the MOSFETs are both off.
--
Regards,
John Popelish
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