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IR pair circuit troubleshooting

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i am following a circuit of ir pair which i have seen in many tutorials
the circuit is given in the picture..i did followed same as the circuit but i dont know why its not working..
will any one please look at my circuit and just let me know where iam wrong..
the led connected is supposed to be off when some obstacle is in front of ir pair...
but its keep in the on state
 

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I think I found your problem. You've connected to output B whilst using the +/- inputs for A (assuming you are using the LM358 as the schematic suggests). With the inputs for B floating it is likely swinging its output at some high frequency making it look like the output is on. Connect your LED to the correct output and tie the inputs of B to the rails.

additionally:
from what I can see it looks like you have your Tx & Rx diodes the correct way around buts its worth double checking.

The other thing I noticed is that you have pins 2 and 3 swapped compared to the schematic, was that intentional and why have you done that?

The LM358 can only sink 8mA (while it can source 20mA) I'd question if that's sufficient current for your LED, but as you say its stuck in the on state so I guess it must be.
 
You have the Rx photo diode connected so it does nothing. R1 causes the + input of the opamp to always be at the supply voltage so the output LED should never light up.

A reverse-biased photo-diode leaks a tiny current when it has light so the resistor R1 should be 1M, not 10k.
The inputs of an LM358 work properly from 0V to 1.5V less than its supply voltage so you should have the resistor R1 connected to ground with the photo diode connected to the supply voltage but the input bias current of an LM358 opamp is too high for a 1M resistor to ground.

You have a low current in the IR LED so it will be fairly dim.

Here is how a reverse-biased photo diode works:
 

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You have the Rx photo diode connected so it does nothing. R1 causes the + input of the opamp to always be at the supply voltage so the output LED should never light up.

A reverse-biased photo-diode leaks a tiny current when it has light so the resistor R1 should be 1M, not 10k.
The inputs of an LM358 work properly from 0V to 1.5V less than its supply voltage so you should have the resistor R1 connected to ground with the photo diode connected to the supply voltage but the input bias current of an LM358 opamp is too high for a 1M resistor to ground.

You have a low current in the IR LED so it will be fairly dim.

Here is how a reverse-biased photo diode works:

i have seen the same circuit i am following in a development board of arduino... and actually i have copied my circuit from there.. i have seen that 10 K resistance is connected at the photo diode.. and its working fine always
 
You have the Rx photo diode connected so it does nothing. R1 causes the + input of the opamp to always be at the supply voltage so the output LED should never light up.

A reverse-biased photo-diode leaks a tiny current when it has light so the resistor R1 should be 1M, not 10k.
The inputs of an LM358 work properly from 0V to 1.5V less than its supply voltage so you should have the resistor R1 connected to ground with the photo diode connected to the supply voltage but the input bias current of an LM358 opamp is too high for a 1M resistor to ground.

You have a low current in the IR LED so it will be fairly dim.

Here is how a reverse-biased photo diode works:

i have seen the same circuit i am following in a development board of arduino uno... and actually i have copied my circuit from there..
and its working fine there

look these are the pics of the board part containing IR pair ckt... and the ir pair on the board works fine the out is connected to the 1 pin of lm358... i also tried it but it doesnt work.. in fact once a time when i was doing on breadboard when i connect the out to 7th pin.. the circuit works... but after 5 minutes it does'nt
 

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I think I found your problem. You've connected to output B whilst using the +/- inputs for A (assuming you are using the LM358 as the schematic suggests). With the inputs for B floating it is likely swinging its output at some high frequency making it look like the output is on. Connect your LED to the correct output and tie the inputs of B to the rails.

additionally:
from what I can see it looks like you have your Tx & Rx diodes the correct way around buts its worth double checking.

The other thing I noticed is that you have pins 2 and 3 swapped compared to the schematic, was that intentional and why have you done that?

The LM358 can only sink 8mA (while it can source 20mA) I'd question if that's sufficient current for your LED, but as you say its stuck in the on state so I guess it must be.

pin 2 is connected to the node between ir receiver and 10 k resistance
and pin 3 is connected to the potentiometer center pin.. (where is swapping?)
and led always illuminate does not go off.. when obstacle is infront of it
 
pin 2 is connected to the node between ir receiver and 10 k resistance
and pin 3 is connected to the potentiometer centre pin.. (where is swapping?)
and led always illuminate does not go off.. when obstacle is in front of it
Take another look at the schematic you posted. Pin 3 is connected to the node between ir receiver and 10 k resistance
and pin 2 is connected to the potentiometer centre pin ... so you've swapped the inputs around compared to the schematic.

Also you're missing the point, your circuit if you're expecting an output from device B but are inputting to device A! Look again at the LM358 datasheet
 
Actually looking at the board photos in #5 it would seem you've drawn the schematic wrong in terms of pin 2/3 and actually your circuit is correct.

However look again at the underside of the board photo in #5 and you'll see the output is connected to pin 1, in your circuit you've connected it to pin 7.
 
The circuit schematic might work if the dual opamp is a TL082 that has inputs that work at its positive supply voltage.
 
The circuit does not have a 330 ohm resistor as you show.
I was correct, the Tx LED does not have low current from a 10k resistor, instead it has high current from a 220 ohm resistor.
 
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