I want to control the speed of a fan (which is a 2-phase brushless DC motor). I am currently using a suitable power supply to run the fans. My source is a Data Acquisition device that outputs up to +10VDC but only drives 5mA maximum. I want to supply up to 1.5A and about 24VDC to the fan.

I was thinking of using a motor driver, and I found several but they usually require at least 6mA of current to run the motor driver, with a typical voltage input of between 6.4 and 7VDC. Is the combination of data acquisition device and motor driver sufficient?

Are there better alternatives out there? Again, I would like to control the speed of fan using the data acquisition device only, not having to use a power supply.


You are confusing signal currents and supply current. If you are using motor driver connected to your IO card, it will supply the control signals to it at low currents. In the same time the motor driver has to be fed with external high power supply, sufficient for motor driving. If you can implement a switching algorithm using your IO card, an H-Bridge will be sufficient for driving the fan.

  • \$\begingroup\$ Got it. Please elaborate on switching algorithm. \$\endgroup\$ – Ryan Jan 20 '15 at 20:52
  • \$\begingroup\$ Look here: gaw.ru/pdf/Atmel/app/avr/AVR440.pdf I guess your fan has no sensors on it, so the sensorless technique is the only available. But it is not that easy, so on the second though, it might be better to use some dedicated controller. \$\endgroup\$ – Eugene Sh. Jan 20 '15 at 20:59
  • \$\begingroup\$ Thank you. So a motor controller would be a better idea than an H-Bridge (like ti.com/lit/ds/symlink/sn754410.pdf) that is controlled through my data acquisition device through Labview? \$\endgroup\$ – Ryan Jan 20 '15 at 21:11
  • \$\begingroup\$ Yes. It will save you the hassle of developing the algorithm, which I am not sure is feasible with labview (since it has to be strict real-time and high speed). \$\endgroup\$ – Eugene Sh. Jan 20 '15 at 21:15
  • \$\begingroup\$ Sounds good. To summarize, I have my data acquisition device plus labview program that goes to a motor driver/controller. The motor controller/driver has an external power supply connected to it. The signal from the motor controller/driver goes to the fan. The labview program should be able to control the fan. Is that correct? Now, should I be using the analog output or the digital output of the data acquisition device? Thank you so much \$\endgroup\$ – Ryan Jan 20 '15 at 21:46

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