photodiode using opamp output problem

[hiren.dave@bhuved.com]

HI,

i am using photodiode with opamp as a photoconducting method. I am getting output well but output contains pulses. I can't understand that why photodiode and amplifier is generating pulses. help me to solve this problem. i am View attachment 65078View attachment 65079attaching circuit and dso output herewith.

 

[cowboybob]

Circuit looks a tad naked.

Are VCC and 12VDC supply for photoresistor one and the same?

Looks like the LM324 is self-oscillating.

Look at this schematic. A little more complicated but it might help you see how to go about it with an OpAmp.

View attachment 65080

 

[KeepItSimpleStupid]

Look at the specs for that OP amp. I believe it's output is limited to about 200 mV above ground and Vcc-1.2V. You can't bias the input at the supply voltage. That's the fundamental problem.

 

[hiren.dave@bhuved.com]

ok. friend. i am checking this.

 

[hiren.dave@bhuved.com]

hi, i checked this circuit. but it gives 12V constant at output. I am giving VCC of 12V. i can't understand that why output is 12V?

 

[WTP Pepper]

I can. You are forcing the input via leakage to -12V leaving the op-amp to saturate at +12V.

 

[cowboybob]

Pepper is correct about the biasing.

Try these: (different OpAmp, but concept is the same)

View attachment 65099 View attachment 65100

 

[hiren.dave@bhuved.com]

hi wtp and cowboy..

i will try the circuit that you have given me. i will reply soon.


thanks...

 

[hiren.dave@bhuved.com]

hi. i want to give photodiode to -12v. i am connecting anode of photodiode to gnd of battery. is it correct configuration or not??

 

[hiren.dave@bhuved.com]

finally i got the amplified output. i am giving you a circuit......
View attachment 65145

 

[WTP Pepper]

That's a horrendous amount of gain in a single stage of an op-amp that's just not upto it. You would need a fair amount of error correction on a coded signal through your implemtation.

 

[dr pepper]

A circuit I found on the web, also uses lots of gain, its only intended to test remote controls and probably isnt much good for sending data.

https://translate.google.com/transl...://www.soloelectronica.net/comprobador_ir.htm

You can get infra red receiver modules, like a tssop37, these have an amplifier and an output driver built in, only thing is they respond to 37 khz tone bursts rather than a continuous source of infra red.

 

[WTP Pepper]

If you want to see if your TV remote is working, point it at your phone cam/digital cam or camcorder.
You will see the IR as white bursts of lights on the display.

The CCD sensor on a digital camera is sensitive to IR emitted from IR LEDs found in such remotes.

 

[dr pepper]

Yep I use the above to check and align industrial infra red barriers on machinery.