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Postby Samuel2445 » Tue May 24, 2016 1:51 pm

This is kind of a two part question really,

Firstly, would I be able to use the PiBorg to control a 12v DC PC Fan and change the speeds with the PWM as stated in the product description?

Secondly, If I can then would it be possible to use 2x 12v DC PC Fans on the same pin? As I need both Fans to run at the same speed.

Link: http://www.modmypi.com/raspberry-pi/bre ... rch=piborg

Any help would be great!

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Postby PiBorg » Tue May 24, 2016 3:12 pm

Unfortunately the PWM will not work with most PC fans :cry:

Typical PC fans are powered by a DC connection, but they are actually a BLDC motor and have a tiny control chip inside them.
If you use PWM on these the control chip gets upset and does not rotate the fan correctly.

The PicoBorg would work with them for on/off control, it is just the PWM which does not work as intended.

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Postby Samuel2445 » Tue May 24, 2016 3:55 pm

Many thanks for your help!

Would you be able to recommend a method for getting the fans to have controlled speed?

Samuel2445
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Postby PiBorg » Tue May 24, 2016 4:55 pm

If you are happy to do some soldering / breadboarding you can probably get this to work by adding a smoothing circuit.

The smoothing circuit will take the PWM output and make it more like a constant voltage level.
This will keep the controller chip happy and allow you to use the PicoBorg normally.

A resistor and a capacitor should be enough to try this.
There is a good explanation of how it all works here: http://provideyourown.com/2011/analogwr ... o-voltage/

To work out the values you want there is a calculator here: http://sim.okawa-denshi.jp/en/PWMtool.php
The frequency used in the examples is 100 Hz.
Vl should be 0.
Vh should be the same as your input (battery) voltage.

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