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Author Topic: LM317 Help  (Read 4294 times)
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Arlington, MA, USA
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Cool! Would 2 "forever" stamps be sufficient postage? Maybe 3 to be sure, eh?

Under Terry's name it says "Red Sea/Saudi Arabia" so my guess would be "no."
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For the divider I'm not sure if 1k resistor and a 18uF capacitor will suit my needs...

For the fan control I will be regulating 12V, the voltages which will be "available" for the fans are: 7V, 8V, 9V, 10V, 11V, 12V and will be changed as the temperature of the CPU Changes. I'm expecting the voltage change to occur no higher than 2x a second.
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For the divider I'm not sure if 1k resistor and a 18uF capacitor will suit my needs...
I am not sure where you got these values from. An 18uF capacitor is very non standard, 10uF , 16uF and 22uF are the closest values.
However, it is not very critical as it is only a second order filter and the slope here is not steep.
 
You will have to experiment as to what PWM values you have to get to give those voltages to the fan. This is because you are relying on the non saturated part of the curve and it is not consistent from device to device.
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I'm currently "worried" so to say about the divider.

Will it allow me to change the voltage 2x a second?
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1K and 18uF is a time constant of :-
1 103 X 18 10-6 = 0.018 seconds
So yes it will not hamper a signal at 0.5 seconds period.
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Ok, so I finnaly got my hands on all the parts I need, but there's a problem... It's not working smiley-sad

When I tap the FET the fan starts spinning and if I don't do that nothing happens...

I'm guessing that the FET is damaged, but am not sure...

What do you think?
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Under Terry's name it says "Red Sea/Saudi Arabia" so my guess would be "no."
I believe that Terry also has a residence in Vermont.

Don
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Under Terry's name it says "Red Sea/Saudi Arabia" so my guess would be "no."
I believe that Terry also has a residence in Vermont.

And, in fact, he's there now. Having some trouble with the forum though.
http://arduino.cc/forum/index.php/topic,65627.msg480338.html#msg480338
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No like this

                                                                     12V
                                                                       |
                                                                   Load(Fan)
                                                                       |Drain pin
                                                                       |
|Digital Pin 9|----|Resistor|-------------Gate--|MOSFET|
                                                |                     |
                                         |Capacitor|            |Source pin
                                                |                     |
                                                |                     |
                                                |                     |
                                                |                     |
                                                |                     |
                                              GND                GND

The way you had it:-
1) the capacitor would block the DC signal and nothing would get too the gate
2) you would not get any more than 5V across your fan

hello can you provide code? thls
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