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Help Regarding Ir Sensors As Object Detction

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i m using IR leds (without modulation) for the purpose of object detection along with a photodiode which is acting as a reciever for the IR Led and in addition to it the interruption in the ir transmitter RXr module is used to start a timer on. i m using a 555 timer in monostable mode n to the trigger pin of this i m connecting th photodiode n the output of this timer is given to a npn transistor and o/p of the transistor from collector is further given to the relay which gives ouput to the microcontroller.But im facing two problems .Firstly the range problem n secondly the TXr IR led n RXr photodiode are not wrkng in sunlight.cud anyone plz guide me hw can i get rid of these two problems by making modification in the existing circuit.plz reply asap.plzzzzzzzzzzz

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To get good range you need alot of current through your transmiter diode or a diode with a good lens to give you a narrower and more concentrated beam.

 

You can get receiver photo diodes with have a daylight filter built into the lens. They usually look black or dark grey. I have played around with one some time ago and found it was less sensitive to daylight if it was fitted into a dark tube to eliminate alot of the daylight shining onto it. Recess it into the tube a few millimetres.

 

Cheers

 

Reynard

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To get good range you need alot of current through your transmiter diode or a diode with a good lens to give you a narrower and more concentrated beam.

 

You can get receiver photo diodes with have a daylight filter built into the lens. They usually look black or dark grey. I have played around with one some time ago and found it was less sensitive to daylight if it was fitted into a dark tube to eliminate alot of the daylight shining onto it. Recess it into the tube a few millimetres.

 

Cheers

 

Reynard

 

thanx

If i think of modulating the ir signal at 38khz will that help in solving both the range n sunlight problem.besides this cud u plz tell me the circuit for the same.

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Modulating the signal will act like a digital filter allowing only the signal you are interested in being detected and not random interference from anyother IR sources.

 

If you want increased range you can try an array of transmitter diodes to increase IR intensity.

 

Modulation won't help the sunlight problem. Once the photo diode is saturated with sunlight it won't see your signal.

 

There are several chip sets out there which will do the modulation/demodulation for you if you don't want the PIC to do it.

 

A Google search should get you some info on the subject.

 

Cheers

 

Reynard

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Modulating the signal will act like a digital filter allowing only the signal you are interested in being detected and not random interference from anyother IR sources.

 

If you want increased range you can try an array of transmitter diodes to increase IR intensity.

 

Modulation won't help the sunlight problem. Once the photo diode is saturated with sunlight it won't see your signal.

 

There are several chip sets out there which will do the modulation/demodulation for you if you don't want the PIC to do it.

 

A Google search should get you some info on the subject.

 

Cheers

 

Reynard

thnx once again.But sir,if i m modulating the IR then a normal photodiode wont be used as RXr.then i vill hav to use the TSOP wich is modulated at a frequency to which the IR is modulated i.e 38khz wich i have thought of.n the TSOP IC is black cased n i think it will act as daylight filter. cud plz guide me in this regard.

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I assume you are referring to the TSOP1738 type of device for the reciever.

 

It seems like a good device to use. Remember the data rate (baud) will be low but it all depends on what you intend to use it for.

 

It has an ambient light filter but within reason. It is OK for an indoor environment but don't point it directly at a window where bright daylight is going to shine on it.

 

I like using RF devices from RF Solutions which means no line-of-sight problems.

 

Cheers

 

Reynard

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