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Sci.Electronics.Basics -> Creating a voltage-controlled resistance

There are 26 messages in this thread.
You are currently looking at messages 1 to 20.






Author: David
Date: 10:56 11-09-07

I'm testing rechargeable batteries and would like a voltage-controlled
resistance so I can easily adjust the load with a program.

I'd appreciate recommendations on how to design this.

Thanks,

David





Author: Eeyore
Date: 11:13 11-09-07




David wrote:

> I'm testing rechargeable batteries and would like a voltage-controlled
> resistance so I can easily adjust the load with a program.

Would a controlled current load be suitable ? That's a far simpler design task.

Graham


Author: Phil Allison
Date: 11:15 11-09-07


"David"
>
> I'm testing rechargeable batteries and would like a voltage-controlled
> resistance so I can easily adjust the load with a program.


** Would kinda help to know a few more details.

You testing AAA cells or 2.5 ton submarine batteries ??

What load power levels, what max voltage ...

The * answer fairy * is on holiday and none of us hear can read minds via
usenet.

Get it ???




....... Phil



Author: John Fields
Date: 12:32 11-09-07

On Tue, 11 Sep 2007 10:56:30 -0400, "David"
<davidd31415@yoowhoo.com> wrote:

>I'm testing rechargeable batteries and would like a voltage-controlled
>resistance so I can easily adjust the load with a program.
>
>I'd appreciate recommendations on how to design this.

---
How about numerically controlled instead? View in Courier:



BAT+>------+------+
| |
[128R] |
| |
D |
IN7>-----G |
S |
| |
BAT->------+ |
| |
GND>-------+---+ |
| |
+---|--+
| | |
[64R] | |
| | |
D | |
IN6>-----G | |
S | |
| | |
+---+ |
| |
+---|--+
| | |
[32R] | |
| | |
D | |
IN5>-----G | |
S | |
| | |
+---+ |
| |
+---|--+
| | |
[16R] | |
| | |
D | |
IN4>-----G | |
S | |
| | |
+---+ |
| |
+---|--+
| | |
[8R] | |
| | |
D | |
IN3>-----G | |
S | |
| | |
+---+ |
| |
+---|--+
| | |
[4R] | |
| | |
D | |
IN2>-----G | |
S | |
| | |
+---+--+
| |
+---|--+
| | |
[2R] | |
| | |
D | |
IN1>-----G | |
S | |
| | |
+---+ |
| |
+---|--+
| |
[R] |
| |
D |
IN0>-----G |
S |
| |
+---+

All the MOSFETs are N channel and you select the voltage, channel
resistance, and dissipation depending on what kind of battery you're
testing. Also the load resistances.

Put a shift register on the MOSFET gates and you can control the
whole thing with 3 bits of data.


--
JF

Author: Don Bowey
Date: 14:40 11-09-07

On 9/11/07 9:32 AM, in article a6fde31tqnppd33t5365joru47d5f8its7@4ax.com,
"John Fields" <jfields@austininstruments.com> wrote:

> On Tue, 11 Sep 2007 10:56:30 -0400, "David"
> <davidd31415@yoowhoo.com> wrote:
>
>> I'm testing rechargeable batteries and would like a voltage-controlled
>> resistance so I can easily adjust the load with a program.
>>
>> I'd appreciate recommendations on how to design this.
>
> ---
> How about numerically controlled instead? View in Courier:
>

Snip

> +---|--+
> | | |
> [4R] | |
> | | |
> D | |
> IN2>-----G | |
> S | |
> | | |
+---+ |<<<< had a jumper to 'S' here.
> | |
> +---|--+


Snip

> All the MOSFETs are N channel and you select the voltage, channel
> resistance, and dissipation depending on what kind of battery you're
> testing. Also the load resistances.
>
> Put a shift register on the MOSFET gates and you can control the
> whole thing with 3 bits of data.
>


Author: John Fields
Date: 14:57 11-09-07

On Tue, 11 Sep 2007 11:40:05 -0700, Don Bowey <dbowey@comcast.net>
wrote:


>Snip
>
>> +---|--+
>> | | |
>> [4R] | |
>> | | |
>> D | |
>> IN2>-----G | |
>> S | |
>> | | |
> +---+ |<<<< had a jumper to 'S' here.
>> | |
>> +---|--+
>
>
>Snip

---
YOW!!! Thanks. :-)


--
JF

Author: Jamie
Date: 19:03 11-09-07

David wrote:
> I'm testing rechargeable batteries and would like a voltage-controlled
> resistance so I can easily adjust the load with a program.
>
> I'd appreciate recommendations on how to design this.
>
> Thanks,
>
> David
>
>
>
>
Assuming you're talking about microchip processor coding or maybe
even from the PC port?
You can pulse width modulate (PWM).And drive a switching device like
a Power fet or bipolar transistor to regulate. Of course, you should also
monitor current. This would mean a device that has either a ADC (
Analog to Digital Converter) or, use a series of voltage comparator as
ranges to activate a few IO lines as inputs.

There are small AVR's and PIC chips that have this ability.
My self, for this, I would use an AVR. But that's my preference.


Most Uc's have a PWM function in it that will use an IO or, you
can make one via a timer function.

I don't know where you are at the level of electronics with this?

--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5


Author: David
Date: 22:03 11-09-07


"Phil Allison" <philallison@tpg.com.au> wrote in message
news:5knpp9F4nmrqU1@mid.individual.net...

>
> The * answer fairy * is on holiday and none of us hear can read minds
> via usenet.
>
> Get it ???
>

Hear hear!

The others who have responded will be plenty of help, your pompous attitude
surely has a better use elsewhere.









Author: David
Date: 22:12 11-09-07


"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in
message
news:AWEFi.51$ss5.20@newsfe04.lga...
> David wrote:
>> I'm testing rechargeable batteries and would like a voltage-controlled
>> resistance so I can easily adjust the load with a program.
>>
>> I'd appreciate recommendations on how to design this.
>>
>> Thanks,
>>
>> David
>>
>>
>>
>>
> Assuming you're talking about microchip processor coding or maybe
> even from the PC port?
> You can pulse width modulate (PWM).And drive a switching device like a
> Power fet or bipolar transistor to regulate. Of course, you should also
> monitor current. This would mean a device that has either a ADC (
> Analog to Digital Converter) or, use a series of voltage comparator as
> ranges to activate a few IO lines as inputs.
>
> There are small AVR's and PIC chips that have this ability.
> My self, for this, I would use an AVR. But that's my preference.
>
>
> Most Uc's have a PWM function in it that will use an IO or, you
> can make one via a timer function.
>
> I don't know where you are at the level of electronics with this?
>
> --
> "I'm never wrong, once i thought i was, but was mistaken"
> Real Programmers Do things like this.
> http://webpages.charter.net/jamie_5
>
>

I have a DAQ card to control the active resistance and sample the
current/voltage. Plan to use a shunt resistor to monitor the current. I
studied transistors in college years ago but am quite rusty. You're
suggesting using PWM to control the resistance? I'd like to drain the
batteries with a steady current, wouldn't that cause it to alternate?



Author: David
Date: 22:15 11-09-07


"John Fields" <jfields@austininstruments.com> wrote in message
news:a6pde31sfvl1pbk8ifqvup9huovt3pupeb@4ax.com...
> On Tue, 11 Sep 2007 11:40:05 -0700, Don Bowey <dbowey@comcast.net>
> wrote:
>
>
>>Snip
>>
>>> +---|--+
>>> | | |
>>> [4R] | |
>>> | | |
>>> D | |
>>> IN2>-----G | |
>>> S | |
>>> | | |
>> +---+ |<<<< had a jumper to 'S' here.
>>> | |
>>> +---|--+
>>
>>
>>Snip
>
> ---
> YOW!!! Thanks. :-)
>
>
> --
> JF
>

I think something like this will work. I wasn't envisioning discrete levels
at first but there should be no problem doing it that way.

Thanks!



Author: Phil Allison
Date: 23:35 11-09-07


"David"
"Phil Allison"
>>
>> The * answer fairy * is on holiday and none of us hear can read minds
>> via usenet.
>>
>> Get it ???
>>
>
> Hear hear!
>
> The others who have responded will be plenty of help,


** You fucking vile little SHITHEAD !!!!!!!


> your pompous attitude surely has a better use elsewhere.


** I would tell you to

GO FUCK YOUR MOTHER

- if I were not so sure you were already.





....... Phil





Author: Phil Allison
Date: 23:36 11-09-07


"David"


** Go get CANCER and die


YOU STINKING ASSHOLE





........ Phil



Author: Phil Allison
Date: 23:37 11-09-07


"David the ASININE PILE of SHIT "


** DROP DEAD

You vile autistic CUNT !!!




....... Phil



Author: David L. Jones
Date: 01:21 12-09-07

On Sep 12, 12:56 am, "David" <davidd31...@yoowhoo.com> wrote:
> I'm testing rechargeable batteries and would like a voltage-controlled
> resistance so I can easily adjust the load with a program.
>
> I'd appreciate recommendations on how to design this.
>
> Thanks,
>
> David

All you need is a suitable MOSFET and a resistor and opamp, this will
create a constant current load based on your input voltage.

Just like in this schematic here:
http://alternatezone.com/files/A3746-BatterySAVR-Schematic.pdf
This is a battery discharge logger that can give you constant current,
constant resistance, or a constant power load depending on your needs.
But you don't need anything but the MOSFET, opamp and resistor load to
give you constant current, just adjust the voltage on the opamp input.

Constant resistance and constant power loads are created under
software control.

If you want more details on this project, let me know.

Dave.


Author: Eeyore
Date: 02:01 12-09-07



David wrote:

> I have a DAQ card to control the active resistance and sample the
> current/voltage. Plan to use a shunt resistor to monitor the current. I
> studied transistors in college years ago but am quite rusty. You're
> suggesting using PWM to control the resistance? I'd like to drain the
> batteries with a steady current, wouldn't that cause it to alternate?

What's an alternating battery ?

A PWM'd DC load current is still a DC load.

Graham



Author: PhattyMo
Date: 02:03 12-09-07

Phil Allison wrote:
> "David the ASININE PILE of SHIT "
>
>
> ** DROP DEAD
>
> You vile autistic CUNT !!!
>
>
>
>
> ....... Phil
>
>


Aww..come on Phil,You've gotta come up with some new names to call
people.. "autistic cunt" and "stinking asshole" are old news,man.

And what's the obsession with mother-fucking? Should we start calling
you "Ed" with an O?

Author: Jasen Betts
Date: 07:54 12-09-07

On 2007-09-12, David <davidd31415@yoowhoo.com> wrote:
>
> I have a DAQ card to control the active resistance and sample the
> current/voltage. Plan to use a shunt resistor to monitor the current. I
> studied transistors in college years ago but am quite rusty. You're
> suggesting using PWM to control the resistance? I'd like to drain the
> batteries with a steady current, wouldn't that cause it to alternate?

'fluctuate' is probably a better term than alternate.
yes wit would, but that's unlikely to effect the battery
much.

Bye.
Jasen

Author: John Fields
Date: 08:13 12-09-07

On Wed, 12 Sep 2007 07:01:44 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

>
>
>David wrote:
>
>> I have a DAQ card to control the active resistance and sample the
>> current/voltage. Plan to use a shunt resistor to monitor the current. I
>> studied transistors in college years ago but am quite rusty. You're
>> suggesting using PWM to control the resistance? I'd like to drain the
>> batteries with a steady current, wouldn't that cause it to alternate?
>
>What's an alternating battery ?
>
>A PWM'd DC load current is still a DC load.

---
What is it you don't understand about: "I'd like to drain the
batteries with a steady current," dumb ass?


--
JF

Author: Eeyore
Date: 08:38 12-09-07



John Fields wrote:

> Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:
> >David wrote:
> >
> >> I have a DAQ card to control the active resistance and sample the
> >> current/voltage. Plan to use a shunt resistor to monitor the current. I
> >> studied transistors in college years ago but am quite rusty. You're
> >> suggesting using PWM to control the resistance? I'd like to drain the
> >> batteries with a steady current, wouldn't that cause it to alternate?
> >
> >What's an alternating battery ?
> >
> >A PWM'd DC load current is still a DC load.
>
> ---
> What is it you don't understand about: "I'd like to drain the
> batteries with a steady current," dumb ass?

Have you ever heard of LC filters ?

Graham


Author: John Fields
Date: 10:31 12-09-07

On Wed, 12 Sep 2007 13:38:39 +0100, Eeyore
<rabbitsfriendsandrelations@hotmail.com> wrote:

>
>
>John Fields wrote:
>
>> Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:
>> >David wrote:
>> >
>> >> I have a DAQ card to control the active resistance and sample the
>> >> current/voltage. Plan to use a shunt resistor to monitor the current.
I
>> >> studied transistors in college years ago but am quite rusty. You're
>> >> suggesting using PWM to control the resistance? I'd like to drain the
>> >> batteries with a steady current, wouldn't that cause it to alternate?
>> >
>> >What's an alternating battery ?
>> >
>> >A PWM'd DC load current is still a DC load.
>>
>> ---
>> What is it you don't understand about: "I'd like to drain the
>> batteries with a steady current," dumb ass?
>
>Have you ever heard of LC filters ?

---
I see...

Instead of a simple resistive load to drain the battery you're
advocating using an LC filter in front of the PWM 'ed load in order
to get what looks, presumably, like a resistive load to the battery.

Just what I'd expect from a stupid son of a bitch like you, adding
epicycles to epicycles.


--
JF

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