LASER & IR Reciver.

[Ayne]

I found this circuit on NET. I want to ask that this circuit will work for both IR Light and LASER.
And another thing i am replacing +12 Volts with +5 Volts.........and - 12 Volts with 0 Volt(GND).

 

[Ayne]

Pcb

I make the PCB of th two circuit one Nigel IR Board ans second circuit is that i have posted above.

Why i am using above circuit that i have posted already because i want to count reflected light pulses from a surface.

ur views, ideas.
Thanks

 

[audioguru]

A reverse-biased photo-diode is a lot less sensitive than a photo-transistor.
The 5.6k resistor should be a much higher value for the photo-diode to have some sensitivity.

The photo-transistor will have voltage gain if it is common-emitter instead of the emitter-follower.

The comparator should have hysteresis so that it doesn't oscillate, amplify its own noise or amplify noise from the power supply.

 

[AllVol]

Just comparing your circuit with that given as application in the LM393 datasheet,

your Vref (R4) should be on pin 3, and the input from your sensor going to pin 2

 

[audioguru]

Just comparing your circuit with that given as application in the LM393 datasheet,

your Vref (R4) should be on pin 3, and the input from your sensor going to pin 2

It can be either way, depending on if you want the output to go high or go low when the sensor conducts.

 

[AllVol]

Wonder which way he wants it to go?
Wonder if he has considered this?
The way it's shown he's going inverted.

 

[audioguru]

The schematic shows non-inverted.

 

[Ayne]

Need Improvement ???

Two pictures attached,
one circuit given as application in the LM393 datasheet.

And second circuit i made.

Compare both circuits.

What u say that is there any mistake or any suggestion that can increase it's performance,

 

[audioguru]

It is good that you added hysteresis.
The output will be low when there is enough light.
The photo-detector is DC-coupled to the comparator so it might not work when there is high ambient light. IR receiver ICs have the photo-detector AC-coupled with a capacitor so they continue to work during high ambient light.
IR receiver ICs also have a bandpass filter that blocks interference from mains-powered lights, and the light beam is modulated at the tuned frequency.

R2 is a very low value. So the light must be fairly bright to make the phototransistor conduct enough, and the light must be extremely bright to make the photo-diode conduct enough. A reflection won't be bright enough so use 10k, 100k or 1M for R2.

 

[Ayne]

Thanks audioguru

The photo-detector is DC-coupled to the comparator

Yes, because if it will AC coupled then it's output will be low after few moments. Different Language is a great barrier

Now what u say,
Need some improvement???
i will make PCB when u will say that ur circuit is now ready for PCB.

 

[audioguru]

Your circuit is still DC-coupled. The pot can be adjusted for the amount of ambient light and sensistivity.

 

[Ayne]

Your circuit is still DC-coupled.

Suppose our phototransitor is under constant light source if it will be AC coupled then it's output will be droped after few moments as shown in picture (because of capacitor fully charged).
output low means there is no light on the photosensor but the photosensor is under constant light source.
Hope u understand. my poor English.