Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: rahulmagoo on June 10, 2008, 03:19:10 AM

Title: Optocoupler(4N33)
Post by: rahulmagoo on June 10, 2008, 03:19:10 AM

hello,
I have a questions regarding Optocoupler..

I am making a simple line following robot, instead of using ULN 2803(darlington array) and relays can I use optocoupler(4N33).If yes could anyone please help me in using it as i could'n understand it completely from its datasheet.

Title: Re: Optocoupler(4N33)
Post by: Admin on June 16, 2008, 12:47:42 PM

What is it being used for?

Title: Re: Optocoupler(4N33)
Post by: rahulmagoo on June 28, 2008, 01:24:52 PM

I am using my optocoupler(4N33) to drive my motors.

Title: Re: Optocoupler(4N33)
Post by: izua on June 28, 2008, 01:48:01 PM

you can't use an optocoupler to drive motors. 4n33 has a collector current of 150, small motors can sink even 500 mA at startup.
you will have to buffer its output with a transistor or some logic gates

Title: Re: Optocoupler(4N33)
Post by: rahulmagoo on June 28, 2008, 02:02:23 PM

For that can i use a darlington array(ULN 2803).

Title: Re: Optocoupler(4N33)
Post by: izua on June 28, 2008, 11:01:51 PM

remember, ULNs are inverted logic, or low-side switching. You will have to supply + to your motor, and connect the other wire to the ULN. Also, check if you wired your opto correctly using a led. Finally, check if the rest of the circuit works correctly, by removing the optocoupler (if in a socket) and shorting the pins of its output. This way, the rest of the circuit will see as if the optocoupler is "open". Last, do a sanity check to see if you haven't messed up the led polarity :)