5 replies to this topic

[__Pat__]

Hello again! After being given some great ideas for a project here(using temperature sensors, etc..), I finally found one. A heat based fan controller like ones found in the GPU.
However when I asked my professor about the idea, he said that using a fan(motor) with the DAQ USB 6008 would make the DAQ's circuitry fry due to the large power required by a motor. Is that true?

[crelf]

Don't power the motor directly from the USB box - control a relay with it. ie: turn the coil of a realy on and off with the USB box, and then wire the motor with its own power supply to the NO (normally open) contacts of the relay. Now, when you make the digital oputput of the USB box go high, the contacts on the realy will close (just like a switch) and the motor will turn on.

[__Pat__]

The problem is I won't be giving it a digital output, but analogue since I want to control the speed of the motor...

Might I ask why that is that I shouldn't wire the motor directly?

[ned]

Might I ask why that is that I shouldn't wire the motor directly?

For exactly the reason your professor mentioned - the analog output on your USB 6008 (and pretty much any analog output on a similar device) cannot supply enough power to run a motor. The analog output is designed to act only as a control signal. The digital outputs on the 6008 are similarly limited.

[Roderic]

You can control the relay with the analog output if you outpout 0 or 5V.

[Vitoriano]

If you check the spec from usb 6009, you will see that the analog output have a current draw limit, that is not enough to your fan motor,
instead of a relay output, try to use a power mosfet , where the gate will conected to your analog output from 6009, That way you will be enable to control the velocity of the motor using your analog outpout.
There is another solution but more complicate, like PWM controls.
For initialization will be a good project using the mosfet.

Good Luck in the project.