Did I kill my phototransitor?

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tboydva

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I'm trying to put together a bubble counter using this device:

**broken link removed**

My plan was to link to a microcontroller and have it perform a function if the count got above a certain level. I've programmed my controller and it works fine. However, it playing around with the breadboard, I hooked up my 819 device incorrectly. I'm not sure how I had it hooked up, but I remember thinking, "Oh no, I shouldn't have that wire there!" Anyway, now I'm trying to test it using this app note:

**broken link removed**

So, when I hook the red wire (1) through 170 Ohms to 5V and the white wire (3) through a 10K resistor to 5V, with black (2) and green (4) hooked to ground, I get high signal no matter what. I'm guessing I fried it. Can I test it like a transistor? Is there any other way to test or am I still totally missing the right way to hook it up? Any advise would be appreciated.

Thanks
 
hi,
The wiring looks OK. Look at the drawing.

If you have an DVM, try this test for the LED emitter, apply the +5V to the circuit as normal.

Measure the voltage from pin 1 to pin 4, tell us what you read.

Measure the voltage from pin 3 to pin 4, tell us what you read.
 
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Well, just when I was set to remeasure, the batteries in my meter died. They're in the charger now. I put an LED in between pin 1 and 4 and it was lit - no matter what I put between the posts. According to the App note, it should be "open" between the emitter and collector unless there's an obstruction. I get 5 V regardless. I think I musta' done it in. I'll try a measurement between 2 and 3, but my suspicion is that I need to buy a new one! Thanks for the fast answer though.
 
Why not?

I've heard about the high internal discharge of rechargables but I've used one in my DMV and have never had any problems.
 
I did a quick search at work today and I couldn't find any information about rechargeables and remotes or meters? Do you have a source for this info?

I tried the measurements suggested by Eric and I think I blew it. There is 5V between 1 and 4 (I'm guessing no current through the LED). and it stays at 5V when I put my finger through the light path. I'm not sure how I hooked it up, but I must have killed the LED. I have another switch that is smaller (the light path was too short). It shows about 1.2 V on pin 1 so I know current must be flowing through. Oh well, looks like another order is in order!

Thanks for the help
 
hi
The photo detector may still be OK, you could carefully bore a hole thru the emitter side of the slotted opto and insert a new emitter.
Or
take a hacksaw and cut along the slot, retain the detector for another project.
 
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Hero999 said:
Why not?

I've heard about the high internal discharge of rechargables but I've used one in my DMV and have never had any problems.
Click to expand...

Basically much shorter life, you're starting off with only 1.2V instead of 1.5V, and the batteries self-discharge fairly rapidly.
 
 
Thanks all! Perhaps I should save the detector side... With as much junk as I have lying around and as little time I have to work on projects (3 jobs, 2 kids, occasional sleep), I'll likely toss it and just go with a $5 repacement!
TJB
 
Nigel Goodwin said:
Basically much shorter life, you're starting off with only 1.2V instead of 1.5V, and the batteries self-discharge fairly rapidly.
Click to expand...

That's why I use 8.4V NiMH batteries. The only problem is they measure over 11V when hot off the charger which might not be good for some meters.
 
My DVM shuts itself off if it is not used for a few minutes. Its 9V alkaline battery lasts for years.
 
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