Creating a voltage-controlled resistance

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

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

Graham

Reply to
Eeyore

"David"

** 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

Reply to
Phil Allison

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How about numerically controlled instead? View in Courier:



BAT+>------+------+
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Reply to
John Fields

Snip

+---+ | All the MOSFETs are N channel and you select the voltage, channel
Reply to
Don Bowey

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YOW!!! Thanks. :-)
Reply to
John Fields

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.
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Reply to
Jamie

Hear hear!

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

Reply to
David

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?

Reply to
David

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!

Reply to
David

"David"

** Go get CANCER and die

YOU STINKING ASSHOLE

........ Phil

Reply to
Phil Allison

"David the ASININE PILE of SHIT "

** DROP DEAD

You vile autistic CUNT !!!

....... Phil

Reply to
Phil Allison

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:

formatting link
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.

Reply to
David L. Jones

What's an alternating battery ?

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

Graham

Reply to
Eeyore

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

Bye. Jasen

Reply to
Jasen Betts

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

Have you ever heard of LC filters ?

Graham

Reply to
Eeyore

--
I see...

Instead of a simple resistive load to drain the battery you\'re
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Reply to
John Fields

In message , Phil Allison writes

Welcome to my killfile Phil. What an evil thing to say you worthless piece of... Please feel free to flame the heck out of me, maybe while you're battering against my kill file you'll leave everyone else alone.

--
Clint Sharp
Reply to
Clint Sharp

view in fixed font:

batt + | | | s ,--------g n-channel | d mosfet | | | /| | | /-|----+ '--< | | op amp\\+|-, | \\| | Rsense | | Vref-----' | gnd

This is a constant-current load, controlled by Vref. Current=Vref/Rsense I know you asked for a "variable resistance," but you might want to reconsider.

Reply to
gearhead

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