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Voltage Controlled PWM fan controller. Design discussion/brainstorming thread.

post #1 of 3
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I'd like to get into electronics as a hobby and I've been trying to find a project that was worthwhile to start thinking about and eventually working on.

I'd like to take a voltage input, from probably 5-12v. Maybe 0-12 not entirely sure what would be best. Use the analog signal to generate the duty cycle for up to 12 pwm fans.

I'd like it to be very cheap to make and as small as possible in profile.

I've been looking around on the internet for similar projects and I've come across this:

http://www.pcbheaven.com/circuitpages/Voltage_Controlled_PWM_Generator/

They use a triangle wave generator circuit and compare it to a dc voltage input to generate a PWM signal. The problem with that is it's inversely proportionate to the voltage signal. So I would need to invert the pwm signal somehow. Any thoughts are welcome.
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post #2 of 3
Quote:
Originally Posted by SeeThruHead View Post

I'd like to get into electronics as a hobby and I've been trying to find a project that was worthwhile to start thinking about and eventually working on.

I'd like to take a voltage input, from probably 5-12v. Maybe 0-12 not entirely sure what would be best. Use the analog signal to generate the duty cycle for up to 12 pwm fans.

I'd like it to be very cheap to make and as small as possible in profile.

I've been looking around on the internet for similar projects and I've come across this:

http://www.pcbheaven.com/circuitpages/Voltage_Controlled_PWM_Generator/

They use a triangle wave generator circuit and compare it to a dc voltage input to generate a PWM signal. The problem with that is it's inversely proportionate to the voltage signal. So I would need to invert the pwm signal somehow. Any thoughts are welcome.



I've done that before . . . .


You might find this post very interesting:

http://www.overclock.net/t/1395117/diy-voltage-controlled-scalable-pwm-controller

At the beginning, you'll see the easiest way to produce a voltage controlled PWM signal with a pair of 555 timer chips and a LM311 comparator.

Further along, you'll see what it took to make it work perfectly from a Lamptron CW611.

The harder part was working out some isolation for the control voltages so it could be easily calibrated without one calibration pot wreaking havoc with the other settings.

Once you have that figured out, you need to manipulate the variable voltage from the controller to a range that works for the 311 chip.

You'll be learning op amp circuits for summing, differencing and buffering.


If you plan to do it all in a microcontroller, you'll still have to perform the level translations via analog to get in the range the mcontroller can work with.


It'll be fun.

Darlene

BTW,

Do you have a scope yet, and a higher grade multi-meter with duty cycle and frequency scales.

Here's a few worth looking at:

http://www.mcmelectronics.com/product/GW-INSTEK-GOS-620FG-/72-9850

This one has a built in function generator, but the picture model doesn't match the description, the 620 doesn't have the display, the more expensive one does.

For more budget minded choices, there's PC based scopes:

http://www.mcmelectronics.com/product/TENMA-DSO2090-/72-10155?utm_expid=8634549-20.QlUUB9VpRc2V-fYTYAiBVg.0&utm_referrer=http%3A%2F%2Fwww.mcmelectronics.com%2Fbrowse%2FPC-Based-Oscilloscopes%2F0000002036

I use the 100mhz version of this one, and see these models as a good value.



Less expensive and lower spec'd, this one is kind of an all in one lab for entry level students/hobbyists.
It also has the built in function generator.

You may find it very useful to have the function generator as you learn electronics.

http://www.mcmelectronics.com/product/VELLEMAN-SA-PCSGU250-/72-8660
Edited by IT Diva - 3/17/14 at 4:57am
post #3 of 3
A simple microcontroller will get you covered - with more resolution that you might ever need.

If you don't care about being overly efficient, get those mini Arduino sticks. Plenty enough!
PIC 12Fs and ATTiny MCUs are about as inexpensive and small you can get.

If you're feeling lazy I could even write the code for you tongue.gif It's a handful of lines.
Edited by Artikbot - 3/18/14 at 11:09am
   
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