Brushless control over PC's parallel port

[black_hawk98]

Hello !

I hope someone here can help ! I'm trying to control a brushless motor taken from an old HDD (i guess it's sensorless because it only has 3 wires, green, red, black) through the computer's parallel port for testing purposes. Does anyone here knows of such a project or some documentation about this issue ? I need the circuit as simple as possible and to be able to set the speed by sending the signals over the LPT.

Please HELP !

Than you in advance,
Cosmin

[sesat]

9 FETS need more lines for control than the parallel port has. If I misunderstood, and you want the parallel port to generate the PWM to connect to a hobbby BLDC controller, then you need to run a real time operating system on your computer or something to that effect.

Look at just buying off the shelf a SSC II (serial servo controller) and a Castle Phoenix 10. Why recreate the code and hardware of these from scratch?


Ram

[black_hawk98]

Hi!

I don't want to connect it to a BLDC controller. I want the parallel port to drive the motor. I mean to send the signals to the FETs. It's not so complicated but I kind of lack inspiration right now... so I would appreciate any ideas.

Thanks,
Cosmin

[rjet]

I am not sure if it will work to drive a brushless motor without sensors, but the parallel port can easily drive a few logic level mosfets and you might want to use a split-rail supply for simplicity.

Also the windows operating system of your computer multithreads cpu time, which will probably cause problems for the timing of a sensorless motor, but if you boot your computer to DOS then you can control every cpu cycle and ramp the motor speed gradually up to speed. I frequently do this for time critical driving of robot servos.

[Bruce Abbott]

You need 6 outputs to drive the FETs eg. D0~5, and 3 inputs from the rotor position sensors eg. ACK, BUSY and PE.

Here's my idea of what the circuit might look like (note that due to laziness, I have only drawn 1 of the 3 sensor comparators). The high side driver transistors are configured to hopefully prevent both high and low side FETs from turning on at the same time (which would create a short circuit). Depending on the voltage levels your parallel port can produce, it might be necessary to include pullups or buffers on the low side data outputs.

[black_hawk98]

Thanks for the schematic Bruce ! Would it work without the feedback from the motor ?

[Mr.RC-CAM]

It might be easier to just have the PC control a purpose specific brushless motor IC. Perhaps something like this: http://www.allegromicro.com/sf/8904/ . It requires three wires for a full PC interface.

RC-CAM

[black_hawk98]

@Mr. RC-CAM

I was thinking to use the UC2625DW from Texas Instruments. It's more or less the same as the one you mentioned with the only difference that I have a few of them laying around :) .

BTW Nice work on the NavLights project ! I've built two of them and a LoMA and they work excellent !

Cosmin