Creating a voltage-controlled resistance

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

Graham

"David"

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

On Tue, 11 Sep 2007 10:56:30 -0400, "David" wrote:

--- 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

Snip

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?

Hear hear!

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

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?

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!

"David"

YOU STINKING ASSHOLE

........ Phil

"David the ASININE PILE of S*IT "

You vile autistic CUNT !!!

....... Phil

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:

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

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

Dave.

What's an alternating battery ?

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

Graham

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

Bye. Jasen

Have you ever heard of LC filters ?

Graham

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.

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.