Maker Pro
Maker Pro

Sensing circuit for line following robot

Areeha Durrani

Jul 8, 2015
45
Joined
Jul 8, 2015
Messages
45
I have been trying a no of IR sensing circuits for my line following robot but since it's my first time,em facing a no of problems... I have been trying circuits using IR transmitter and receiver and LM324 but continuously em getting 0 at the output of serial monitor in the arduino..
 

cjdelphi

Oct 26, 2011
1,166
Joined
Oct 26, 2011
Messages
1,166
either your circuit is wrong or the opamp is faulty...

are you measuring a voltage across the ir led when it's operational?
 

Colin Mitchell

Aug 31, 2014
1,416
Joined
Aug 31, 2014
Messages
1,416
The first thing you do is put a 10k pot in place of the 10k and IR receiver and adjust the pot and let us know if the output immediately changes from LOW to HIGH.
 

Arouse1973

Adam
Dec 18, 2013
5,178
Joined
Dec 18, 2013
Messages
5,178

You are using an op-amp as a comparator which is something I try to discourage.

But you have designed it now, and I think R2 is too high, you are using a photodiode which won't have a huge amount of current gain versus irradiance. Can you tell us what IR devices you are using.

Edit R2 is too low a value.

Thanks
Adam
 
Last edited:

Areeha Durrani

Jul 8, 2015
45
Joined
Jul 8, 2015
Messages
45
Sir,is it possible that I don't use the comparator and make the sensing circuit without it?i am new to all this,that's why want someone to guide me...I also want to confirm that I am checking the output at the first pin of IC and in order to check the results,I have connected it to the second digital pin of arduino and the code is something like:
VoidSetup(){
PinMode(2,OUTPUT);
Serial.begin(9600);
Serial.println((digitalRead(2));
}
 

Areeha Durrani

Jul 8, 2015
45
Joined
Jul 8, 2015
Messages
45
Instead of input,I wrote output...
Sir,i just removed the resistor with IR receiver and directly connected it with 5V and changed 330 Ω with 220Ω,so I got 5.32v at pin 1 of IC...but still 0 output at the serial monitor of arduino..why?i don't get it...
 

Arouse1973

Adam
Dec 18, 2013
5,178
Joined
Dec 18, 2013
Messages
5,178
Increase the value of R2, 470K. You still haven't told us what devices you are using. How far apart are the TX and RX devices?
Adam
 

Colin Mitchell

Aug 31, 2014
1,416
Joined
Aug 31, 2014
Messages
1,416
I will make it simpler for you.
Replace the IR diode with a 10k resistor. This means you have half rail on the + input. Now adjust the 10k pot and with a LED and 220R on the output you will see the LED come on.
 

hevans1944

Hop - AC8NS
Jun 21, 2012
4,878
Joined
Jun 21, 2012
Messages
4,878
You STILL haven't provided us with part numbers or specifications for the infrared emitter and the diode infrared detector.

Have you used your multimeter to measure the voltage at the cathode of the IR Receiver RX? Measure the voltage there with respect to GND with the light path both blocked and then un-blocked and tell us what you find.

A reverse-biased infrared-sensitive photo-diode is not a very sensitive detector, and even less so if you are trying to use an infrared LED emitter as a detector.
 
Top