Need help with a circut that worked fine and now does not work?

SN96

I built this circuit and it worked fine. Then I tried to wire it to the basic stamp (Homework Board) and then the circuit quit working. The IR emitter & photo transistor has a rating of 150mA but the universal power adaptor I am using for the stamp board has a switch setting of 100mA or 300mA. I had it set to 300mA and I wonder if I fried the devices? The stamp has a built in voltage reulator, but does it regulate current also?



I have set the switch setting to 100mA. Any way I could test my devices to see if they are still ok?

Thanks

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Mike

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pjv

Hi Mike;

To test the optical components:

Disconnect the Stamp, hook up the power as in your schematic, and look at the voltage on the output pin with a volt meter. That should read 5 V with the light blocked, and low with the path open.

The current switch settings on your power supply should have no effect on what you are doing.

Cheers,

Peter (pjv)

SN96

I think the comonets are fried. I tried everything. If I remove the photo transistor and replace it with an LED, the other LED lights up, so the circuit is working but the photo transistor is not. Oh well, it might have happened then I left the photo transistor in for several minutes steady on. I dont know.

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Mike

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PJAllen

Do you have a DMM with a diode check position?

The IRED should test low ohms one direction and hi ohms in the other.

The transistor (in the dark) should test high ohms.

With a 10K resistor, that phototransistor could stay "steady on"·forever.

SN96

I will try using the DMM and see what I get.

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Mike

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