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.
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.