Through beam sensor issue

[Murugesh_89]

Hi,
I have designed a through beam photoelectric sensor.

This works as per the case 1 and 2 and creating problems as per the case 3 in the following image.


I have attached the receiver circuit diagram for this below..


Also for the same transmitter some receiver works for a distance of 80 - 100 mm but some receiver works only for 20 - 30 mm. Why this deviation?

Thanks,
Murugesh

 

[chuckey]

the Vce can be between 130 - 300mV when the transistor is saturated. See :- https://www.vishay.com/docs/81505/bpv11f.pdf. Have you got focusing mirrors/lens?
Frank

 

[Murugesh_89]

thanks frank..

I think even if the Vce is 300 mV, this is not enough to make the transistor Q2 ON as at least 600mV may be required for the base terminal of Q2 to conduct .

By the way, i did not use any lens. I simply kept the front face of transmitter led and photo transistor as open by keeping these two in a block.

 

[anboli]

hi murugesh,
its a simple circuit only...
replace your R3 10k to 47k... and try it...

 

[chuckey]

the reason I gave those figures was to demonstrate that the photodiode has a 3 :1 variation in its performance, like wise the the gain of the transistor will have some variation.
Frank

 

[anboli]

the reason I gave those figures was to demonstrate that the photodiode has a 3 :1 variation in its performance, like wise the the gain of the transistor will have some variation.
Frank

what is that 3:1 variation? cant able to understand.. could you tell me detail...