Author Topic: Optocoupler issue  (Read 1055 times)

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Offline m4ntiTopic starter

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Optocoupler issue
« on: October 01, 2009, 08:05:26 AM »
Hey guys,

We have a serious problem and I'd like to ask you maybe you can help. Me and my cousin (as you probably well know seeing how many times I've posted issues around here lol) are building a simple differential robot which will use a Sharp IR Sensor to evade walls and obstacles - hopefully. We wanted to follow the $50 robot idea but we wanted something a bit better so we went and used DC Motors instead of servos so we can reverse and make it turn on itself (instead of on one of the wheels). So my cousin built a circuit for one DC motor (which will be mirrored on the other one once this one works) which uses octocouplers since - he says - a DC Motor can't be plugged directly to a uC because of the current it uses.

Here lies the problem. Apparently (and I say apparently because I have no idea about electronics) his octocouplers are absorbing too much current. On it's own, the Motor circuit works - plugged directly into the batteries - but plugged to the uC the circuit absorbs current from the uC itself and nothing happens. The C code in the uC is fine - it works with LEDs - but once the circuit is plugged in to the uC nothing happens.

Can someone PLEASE point us to the right direction? I'll try to get him to send me the schematic for what he's doing... maybe it'll help unless someone knows what I'm talking about (which is quite remote).

Cheers guys,

Offline Soeren

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Re: Optocoupler issue
« Reply #1 on: October 01, 2009, 02:01:38 PM »

Did you use a resistor between the I/O-pin of the controller and the optocoupler (OC)?

You could mount a red LED in series with the IR-LED in the OC to see if it works (it might as well be what you have on the other side of the OC that fails).

Please get (and post) the schematic AND the type number of the OC.

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline m4ntiTopic starter

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Re: Optocoupler issue
« Reply #2 on: October 02, 2009, 12:53:32 AM »
Problem solved :) He plugged in a transistor before the OC


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