Servo motor control : pc parallel port

[agpraneet]

How do we go about controlling a servo motor using pc parallel port??
Is it even possible??

I came across many links for stepper but no relevant link for a servo motor

[agpraneet]

Also, the motor i have has 5 wires while on the web, i read of only servos of 3 wires. It is most probably not a stepper ass resistance readings do not comply and are very odd

Also, the motor runs using two wires connected to an adaptor which makes me doubt if it is a servo or not

[allbits]

Its not a servo motor.
Post a pic to remove all the mystery surrounding this mysterious object.

[agpraneet]

http://s686.photobucket.com/albums/v...IMG00083-1.jpg
http://s686.photobucket.com/albums/v...IMG00082-1.jpg
http://s686.photobucket.com/albums/v...t=IMG00081.jpg

I am new to photo sharing so forgive me if the images are not shown

If you can see the images, then the paired wires can be used to run the motor by an adaptor while the other three do not respond to voltage

[allbits]

its a dc motor with an encoder.

[allbits]

It is possible to interface with PC parallel port, but does you PC have one?
You will need a driver.

where did you get this from? did you rip it off from some old machines, or did a shopkeeper rip you off saying this will give 10Kg torque and can be driven at 3v??

[agpraneet]

None of the above
Actually my brother got his from his seniors at college
Is this a pseudo servo motor?? What function does this serve??

My PC has a parallel port so it is not a problem

How do we go about interfacing it?? Is it very complicated?? Till now, I have done very few projects (stepper motor pc interface, rc car pc interface)??

[debu]

@agpraneet: That is 100% a servo motor. To control this kind of servo motor you need slightly complicated circuitry. It can be done using a parallel port, but you will need to be a little clever with the control code and the drive circuitry. I've used the same servo motor in a closed loop vacuum pump (several years ago, so don't ask me for schematics or firmware files), I used a LM629 to control the motor (w.r.t the encoder), a PIC16F72 for positioning, and built a MOSFET drive to power the motor based on the LM629 signals.
Hope this helps.

Regards,

Debu

[agpraneet]

@debu
Thanks for the reply
Can you explain the five wires?? Is it normal as I am confused as 'allbits' said it was a dc motor with encoder. It seemed logical as it also works as a normal dc motor though the rotation is very slow.

Also, What you said about the interfacing, it would take me time to make out as I didn't understand much about it but thanks all the same. It's the best resource I have come across till now.

Please resolve the contention- dc motor with encoder or servo motor

regards
Praneet

[debu]

@agpraneet: A DC Motor with an encode is a servo, don't get confused with the Hobby Servos (which use a Potentiometer instead of an encoder). The 5 wires are (not in order):

1) Motor +
2) Motor -
The above two wires are for the motor. These will go into the motor drive.
3) Vencoder
4) Encoder-A
5) Encoder-B
The above 3 wires are for the quadrature encoder. These will go into the LM629.

The LM629 will give the signals to the motor driver. The LM629 will be controlled using pulse width from your uC (like a hobby servo, except there will be continuous rotation). Study the LM629 datasheet well, it requires a lot of external components (OpAmp, DAC etc.) to correctly work (this part is slightly tricky). You can build your motor driver by simply using 2 N-Channel MOSFETs and 2 P-Channel MOSFETs.

Regards,

Debu

Edit: Another thing, the motors which I had used, required 60v! So, get all the facts in order before building anything.

Edit2: Also, the encoder is optical, and probably works on 5v, use a multimeter and treat the encoder leads as LEDs to find out which lead does what. Passing any wrong voltages will destroy your encoder.