Transistor-triggered photogate

Audioguru

Joined Dec 20, 2007
11,249
No wonder you are confused on the other website you posted this on:
1) You want triggering to occur when the light is blocked but here an answer shows triggering with light.
2) You said you have a phototransistor but actually you have a photo receiver that tries its best to ignore continuous light. It needs IR light modulated in bursts of 38kHz.
3) You want to trigger a huge and powerful SCR with a tiny current that is too low.
4) The last reply shows turning on a transistor with a photodiode when there is light.
I doubt a photodiode produces enough current to drive the transistor, usually a high gain opamp is used.
 

be80be

Joined Jul 5, 2008
2,051
4) The last reply shows turning on a transistor with a photodiode when there is light.
I doubt a photodiode produces enough current to drive the transistor, usually a high gain opamp is used.
I posted it just for clarification. It needs op amp I ran into that one time I got some part's from radio shack they said phototransistors they where photodiodes I had to remake my detectors.


Well Audioguru Is right photodiode needs a lot to drive the scr

But I still say to stop wasting time we need to no what you really have
My bet it's a ir module.

Then the next part if your going to use a photodiode ya or na ?

Or a photo transistor ?

Then what scr do you have

And the bigy break beam or light to dark ?
 
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Audioguru

Joined Dec 20, 2007
11,249
You do not need a lower voltage SCR. You need one that uses much less current than the monster that you have. You were told to use a "sensitive gate" SCR. On the other website I said to use a 2N5061 SCR. I used them 48 years ago.
 
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