Using a 12V 2A power supply direct and with 3V voltage divider?

That is exactly what I was thinking.

These are NOT precision instruments; however, the half dozen I have all correlate nicely with each other and other hardware. I'll find out what it does this weekend. :)

Thanks,

Steve

Tim,

Agreed. I have been away from usenet for the better part of 7-8 years, and I lost that skillset. My biggest regret is that plonking with Google Groups isn't an option.

Lesson learned!

Thanks,

Steve

I see contradiction in your statement. The VR suggested early in the threa d puts out 3V/100mA (max).

Would it be more accurately stated that I wish to produce a 3V, 2mA max pow er supply?

Perhaps, but I definitely want to know what it is.

w

Phil is the source of that assertion. I explicitly stated that I measured t he output of one DMM with another DMM. The DMM that spun the motor MEASURE D 3V, 2mA

Agreed. As I mentioned before, the fan only runs when temperature hits cer tain significant values. I am unable to create that environment reliably t

then I can probably do exactly that.

The values I have measured are consistent with 12V computer fan PWM specifi cations. I realize that ultimately means nothing, but I choose to use it a s supporting data.

Thank you for your help.

Steve

** Why are YOU here ???

Your idiot Q is way off topic, it's got nothing to do with "basic electronics" and is not answerable.

Only one explanation is possible - you are here to amuse yourself and that means you are TROLLING.

What you don't have the brains to see is the ONLY person currently on this NG who is NOT trolling is me.

.... Phil

There is NO contradiction in Tim's statement.

And the 2950 VR would work fine for you, assuming that the 3V 2mA figure you measured was accurate. The 100mA current that the VR is CAPABLE of providing is NOT what it will provide to your load. At 3 volts, it will provide 2mA to your load - again, assuming your measurements are correct. With a fixed voltage supply, it is your load that determines how much current flows.

Add an LED in series with a 100 ohm resistor from the 3V output of the supply to ground, so that when you switch the supply on to activate the fan the LED acts as an on/off indicator.

Ed

Is it possible that the OP's "motor" has an inboard transistor/FET?

You all piqued my curiosity, and I had DuckDuckGo do a quick search on "computer fan 12V pwm speed control circuit". This turned up a circuit based on the Micrel MIC502 "Fan Management IC" (yup, they have a "hardware app" for that!): PWM Fan controller

What's interesting is that this chip produces (at Vdd=12V) 3.75V PWM pulses out, intended to drive a transistor controlling a motor. There's also a "brother" chip, the MIC5021, which does a similar job and assumes it's driving a MOSFET controlling a motor.

Does this shed any light on the subject?

Frank McKenney

--
  ...[B]ecause his martyrdom is thus a power to the martyr, modern 
  people think that any one who makes himself slightly uncomfortable 
  in public will immediately be uproariously popular. ... The 
  assumption is that if you show your sincerity (or even your 
  political ambition) by being a nuisance to yourself as well as to 
  other people, you will have the strength of the great saints who 
  passed through the fire. 
              -- G.K. Chesterton: The Modern Martyr (1908)

Upon taking the fan out of the car, I discovered a few things.

1) Multimeter signal did squat. 2) PWM is +12V potential 3) grounding PWM w/ 0-~5kOhms will cause the fan to run but "pulse" every few seconds, turning itself on and off. >5kOhms = nothing. At the higher resistances, the fan cycles faster and draws less current over a narrow range, probably less than 2kOhms.

So I was totally on the wrong track.

Thanks to everyone for their help.

Steve

Sorry, But I don't know what to make of that, but I don't know that understand your statements either.

I don't understand, in car it did cause the motor to spin, out of car it didn't?

Meaning you measured 12V on the positive lead of the motor? There is a good explanation for that, but I need to know exactly where you leads were placed for the measurement. I grabbed the first site I saw, please view the first schematic drawing, the circuit on the left side. You can see that if you measured from the positive of the motor to ground, you would get 12V, with motor running or not.

Are you saying you can't get the motor to run at full speed out of the car?

Hope that helps, Mikek

Hi Keith, You sounded like you might have been exasperated in your last post, I know the feeling. Here's some info about PWM that may help.

Here's a video showing the output wave form.

Here's a PWM circuit I have built, I used it to control a motor for winding a Tesla coil. It uses a common LM324.

Then there is the 555 timer ic. Google will deliver thousands of pages about 555 PWM circuits.

Here's one with some explanation of the 555 to help with the understanding.

Mikek

** Alouette, gentille alouette,

Alouette, je te plumerai.

... Phil