8 Channel software controlled fanbus with PWM

Posted on Feb 4, 2014

When speaking of fan control, there are generally 2 ways of doing it, linear control, and pulse-width control. The linear control is the most common. The idea is to decrease the voltage to the fan. If the fan is specified to 12 volts, in most cases you can lower the voltage to 6-7 volts. But if you want to go lower, the result is often that your f

8 Channel software controlled fanbus with PWM
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ans won`t even start. Another issue is step less regulation. This requires a variable resistor (rheostat) or a control circuit, using transistors. If you want to run a fan at 7 volts, the remaining 5 volts will have to be burned of as heat in the control circuit or rheostat. The linear control supplies the fan with a constant voltage. But the PWM control generates rapid 12 volt pulses, and the on  and off  timing determines the overall speed of the fans. Until now, the construction of a PWM circuit has been pretty tricky. It requires an advanced circuit to control the different time constants. But with CKControl II, all timing signals are controlled via the software, allowing us to utilize the PC parallel port as 8 individual, fully controllable PWM outputs. You can use the outputs for not only fans, but all kinds of things including Lazer LED`s, Cold Cathode lights as long as the maximum current output doesn`t exceed 0, 8 A for each channel. You could even add a relay and make the software turn your coffee machine on and off! How many fans can we add to the circuit, then That depends on the fans used. The electronic components used are specified to 1 Ampere per channel. With that in mind, we should stay below 0, 8 Ampere, or approx. 10 Watt per channel. A standard 80mm fan typically uses 0, 14 0, 18 mA (1 mA = 1/1000 Ampere). That makes 5 fans per channel a total of 40 fans for all 8 channels. But that`s a rather...

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