Creating a voltage-controlled resistance

[David]

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

 

[Eeyore]

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

 

[Phil Allison]

"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

 

[John Fields]

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.

 

[Don Bowey]

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.

 

[John Fields]

Snip

+---|--+
| | |
[4R] | |
| | |
D | |
IN2>-----G | |
S | |
| | |

+---+ |<<<< had a jumper to 'S' here.

| |
+---|--+

Snip

 

[Jamie]

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?

 

[David]

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.

 

[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 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?

 

[David]

Snip

+---|--+
| | |
[4R] | |
| | |
D | |
IN2>-----G | |
S | |
| | |

+---+ |<<<< had a jumper to 'S' here.

| |
+---|--+

Snip

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!

 

[Phil Allison]

"David"
"Phil Allison"

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 **** YOUR MOTHER

- if I were not so sure you were already.





........ Phil

 

[Phil Allison]

"David"


** Go get CANCER and die


YOU STINKING ASSHOLE





......... Phil

 

[Phil Allison]

"David the ASININE PILE of SHIT "


** DROP DEAD

You vile autistic **** !!!




........ Phil

 

[David L. Jones]

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.

 

[Eeyore]

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

 

[PhattyMo]

"David the ASININE PILE of SHIT "


** DROP DEAD

You vile autistic **** !!!




....... Phil

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

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

 

[Jasen Betts]

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

 

[John Fields]

What's an alternating battery ?

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

 

[Eeyore]

Have you ever heard of LC filters ?

Graham

 

[John Fields]

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.