Devil 07 Posted August 29, 2007 Posted August 29, 2007 I was looking around online a while ago for a descent fan speed controller which could handle a large amount of fans. There are some pretty nice ones out there but after searching for a while I found myself digging through various schematics in the hopes that I could design a multi-fan single channel controller. Basically I wanted all the fans that circulate air through my case to be adjustable from a single-turn pot. What I ended up with was "way over the top and over-kill" according to the chief tech where I work. This thing can handle as many fans as I can hook up to it without exceeding 3A. This thing doesn't vary the voltage to the fans, it varies the "on" time of the DC square-wave, so the fans are always getting 12V. The spacing between the "on" pulses are varied as the pot turns up or down. I figured this method of controlling fan speed was more efficient than the conventional method of varying the voltage to the fan, since feeding a fan 5-11V from a 12V rail creates wasted power. Anyway, here's a few pics of my monster. If I had a water-cooled system I'd like to see what this type of controller would do for varying pump speed. Guess thats next on my shopping list. Share this post Link to post Share on other sites More sharing options...
soundx98 Posted August 29, 2007 Posted August 29, 2007 Very Interesting. How about some more details on it? Share this post Link to post Share on other sites More sharing options...
Bubbaxm2 Posted August 29, 2007 Posted August 29, 2007 Very nice. Share this post Link to post Share on other sites More sharing options...
radodrill Posted August 29, 2007 Posted August 29, 2007 A schematic would be nice to see Share this post Link to post Share on other sites More sharing options...
ebdoradz Posted August 29, 2007 Posted August 29, 2007 ive seen this more then once on on mining machinery. it change to frenquency of the volt supply to the equipement. that way to equipement can varie is speed and always having 600V AC since DC dont have frequency i would like to see a schematic of that Share this post Link to post Share on other sites More sharing options...
radodrill Posted August 29, 2007 Posted August 29, 2007 ive seen this more then once on on mining machinery. it change to frenquency of the volt supply to the equipement. that way to equipement can varie is speed and always having 600V AC since DC dont have frequency i would like to see a schematic of that What the OP did wasn't variable frequency; but rather a Pulse Width Modulation system. By adjusting the time-high and time-low, the "average" voltage the fan gets is regulated; but the fan is always "kicked" with a full 12V. Share this post Link to post Share on other sites More sharing options...
Devil 07 Posted August 29, 2007 Posted August 29, 2007 I'll post a schematic when I get home tonight. The PWM circuit is based on a LM324A. Share this post Link to post Share on other sites More sharing options...
Devil 07 Posted August 30, 2007 Posted August 30, 2007 Well, as soon as I can get my scanner to work I'll post the schematic. Yeah thats right, I do my schematics the old fashioned way. Paper and pencil. Until then I'll give you a rough break down of the circuit. The main part of the circuit is based on the LM324A which is a quad op-amp. The first op-amp is used with a voltage divider to create a 6V reference Voltage for the oscillator. This is used as a virtual ground reference as there is no -12V power supply being used to create the waveform. The next two op-amps are used to create an Oscillator which will feed one side of the comparator. The oscillator is feeding the non-inverting input of the comparator with a triangle wave. Another voltage divider is created using a potentiometer(VR), with the VR's wiper feeding the inverted input of the comparator. With the VR's adjustable voltage divider, this is used as the reference voltage to control the pulse width with respect to the triangle wave through the comparator. Am I loosing anyone? Now that there is a triangle wave feeding one side of the comparator, and an adjustable reference voltage feeding the other side. The pulses on the output of the comparator are used to fire the MOSFET. Basically, the combination of circuits built from the LM324A are used to vary the power pulses driving the load.[fans] A red LED was strapped to the output as an indication of how fast the fans are spinning. Since the LED is being pulsed with power like the fans, it gets brighter as the pulse width increases. Since the width of the pulses are varied to adjust fan speed, the fans are always getting 12V, which helps keep them running at lower speeds than would be possible with a linear power adjustment. The main reason I wanted a multi-fan single channel controller was to use it as an Aux cooling system for my DAW. I figured if I had more fans spinning at lower RPM they would move about as much air as half the fans at full speed. And since its used to cool my DAW, it needs to be as quiet as possible. Share this post Link to post Share on other sites More sharing options...
Devil 07 Posted August 31, 2007 Posted August 31, 2007 Here it is. Share this post Link to post Share on other sites More sharing options...
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