Hello..

I want to design a circuit to interface it with PC's parallel (LPT) port. I know that there must be a circuit in between motor and LPT port. A friend has suggested that i should use a combination of optocoupler and a transistor in this circuit. Now what should be the proper combination or a circuit design, i am confused about it. Please help me to design such a circuit with minimal components and have it interface with PC's parallel port. My future intentions are to control motor's direction thru port input, but first i want to have successfull interfacing with my circuit and obviously a workable circuit design.

thanks, i will wait for your replies.

 

I have done exactly what you said without an opto coupler but using some transistors and a relay. I gave the ov side of the relay a path to ground through the transistor.

I found out this information at http://www.lvr.com
It gives circuit diagrams and also progs.

Cheers.

 

hi

u r facing the same as we faced before while our automatic hydraulic robot need to be control by PC throgh LPT.
as u said we had use the optocouplers and relays to control the solonoid of the control valves.

 

hi,

i think that optocoupler alone is a great choice since its very secure to your parallel port and if the motor draws to much current the optocoupler only maybe damaged "optocoupler is exactly like the transistor but the base of that transistor is controlled through light emitting diode who is separated completely from the collector-base-emitter".

you can use a decoupling capacitor at the motor input supply to damp the overshoot produced by the motor at start up since the capacitor is considered to be a short circuit when its not charged "choose a suitable series resistance with the capacitor", using a 0.1 microfarad will be fine with 10kohms if the overshoot takes no more than '1->3'msec.

 

i have a very helpful link for you, i used similar circuitry to control a 9v motor as the below link (the first symatic for a relay controller)

http://www.hut.fi/Misc/Electronics/circuits/parallel_output.html

 

Use a diode which can take the VTG and current of the motor parallel-backwards (so it doesn't conduct when the motor is running).

 

Try to use PWM (Pulse Width Modulation)

 

try http://www.forth.org/fd/Step.html