problem in Optocoupler Circuit for switching.

[sujan_014]

I am using TLP181 optocoupler for turning on light with 12 v source. The device should turn on when signalled from microcontroller (ATmega128) PortB.0 to input of optocoupler. The curcuit looked simple but although there is voltage from microcontroller, it fails to turn on. What is the problem ?
Optocoupler that I am using is TLP181.

 

[cl10greg]

Verify your connections, measure the current output from the microcontroller, measure the current on the load side. Is the ground common between the two circuits?

 

[sankar.m8]

I think the optocoupler cannot source the current required by the lamp. what type of lamp you are using?..as per the optocoupler datasheet, only it can source 10mA current. Try replacing the lamp with a LED to verify your current demand.

 

[udhay_cit]

Replace the lamp with Resistor & check the voltage with voltmeter... It will not work for tungsten lamp...

 

[sujan_014]

Just as you said, it could not source small lamp but it worked with a LED.

 

[sankar.m8]

Then you need to change the Optocoupler with a better current source capacity which provides the sufficient current to your lamp to glow.

 

[techgreed]

To drive more load, you can either change the optocoupler or drive another transitor from the optocoupler output and drive the bulb with that transistor.

 

[Ogu Reginald]

It depends on the load you connected to the Optocoupler, the TL181 can source a maximum current of about 50mA. Try connecting a bigger transistor between the load and optocoupler.

 

[FvM]

Don't confuse 50 mA maximum rating with reasonable operation current. Suggested collector current is 1 to 10 mA. The available lamp current is presently limited by the 250 ohms resistor.

To select a transistor and other component values, you need to know the lamp specification.