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IR Sensor

Abinaya Sindhu

Nov 3, 2014
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Hi,

I am a newbie. Can anyone please tell me how to connect an IR Led as a transmitter and other as a receiver for obstacle detection.

Thank you.
 

BobK

Jan 5, 2010
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Hi, and welcome to the forum.

What kind of detector are you using? This might be a simple photodiode or phototransistor or it might be a complete detector + demodulator designed to operate at a specific frequency. The transmitter and receiver circuits are different depending on which type.

Please send a link to the specific receiver and the IR LED for more help.

Bob
 

Abinaya Sindhu

Nov 3, 2014
5
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Nov 3, 2014
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Hi,
Thanks for your reply. I'm using a simple photodiode. This is my circuit. I'm getting the output as high always ( even when there's no obstacle). Where am I wrong? Please help.

Thank you.
 

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davenn

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Sep 5, 2009
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do you have an IR filter over the photodiode
if not ambient light is going to stop the circuit working
 

Abinaya Sindhu

Nov 3, 2014
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I don't have an Ir filter. Do I need one? Is there any problem with my circuit? Thanks.
 

BobK

Jan 5, 2010
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Yes, a photodiode cannot pass enough current to pull a 3K resistor low. What are the specifications of the photodiode? You will need to amplify the signal or use a phototransistor, which has the amplification built in.

Bob
 

BobK

Jan 5, 2010
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I doubt that. If your photodiode cannot pull a 3K resistor close to ground, it certainly cannot pull a 220Ω resistor to near ground. If it is working, you have a phototransistor, not a photodiode.

Bob
 

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
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I suspect it won't be very reliable if ambient light can get on it. You need to use modulated infra-red. Then you can use a TV remote control receiver module. When you discover it doesn't work properly, come back and ask about modulated IR.
 
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