IR sensing (simple circuit); LM324 comparator

[smeagull]

Hi, I was testing out a simple IR transmitter and receiver circuit given on this site for an award winning bot:
http://www.kmitl.ac.th/~kswichit/LFrobot/LFrobot.htm
I made the circuit using a Philips LM324 Op Amp chip (for the comparator), but where the datasheet if this chip says it requires a supply voltage of 32 V (D.C.), the guy who made this bot seems to have used only 5 V. Anyhow, we operated the chip at 5 V and the problem I get is that the test LED glows for higher values of potentiometer resistance (wrt the ground end) whereas it should be the other way round. Also we tried to cover the IR LED, and reflect its emmisions, but this has no effect.

[sumandeep1984]

hey smeagull (nice name)...some of my friends call me by this name


Check the datasheet again 32V must be the absolute maximum rating, the operating ranges are much lower

[addy]

it works absolutely fine with 5v supply.....
even i m using the same stuff for ir's
and i believe most of use the same ic/s for comparing...

[addy]

on reception of ir there ll be a fall in the resistance of ir receiver....
check the voltage difference and set something in between as a comparing value....
feed it in the comparator and get the digital outputs...

[vibhorkhanna]

helloeveryone,
i am building a line following robot using at89c51.

i hav one doubt relating to the simple ir circuit....is it that there is only one ir led in between 4 ir receivers(i am using tsop1736s for receiving).

pls reply soon

[addy]

depends on wat range and accuracy u want....
i used thm wid only one transmitter and one receiver tsop...
dey work well.... but if u put a cluster of leds, u may gain accuracy, distance but it may result in over triggering of tsop too....
so it depends on ur application....

[ankitmutha]

hey guyz!!
plz i need some help..
I'm using AtMega8 for my LFR control system and lm324 for Ir sensing.
Im giving 5v to drive lm324.
the ouput on lm324 wen it's high is 3.6-3.8v
i want to know if this voltage is enough to be fed directly into Atmega8???

[ashish_agarwal123456]

yes its enough.

[ankitmutha]

i dont know... im not sure...
see this is my first hand experience with avr programming and i tried to take input from portd and port c (from the sensor circuit). But i dont get any input at all....
there can be two problems:
1)I'm making mistake in taking input as in i dont know wat statements to write for taking input.

I tried following:

code:

DDRC=0x00;
if(PIN==0x00)
{
//motor control
}

i even tried to set 1's in portc register(not sure about the pull up and pull down resistor thing)

PORTC=0xFF;

but this doesnt work.

2) second explanation would be that there's a difference in the voltage values.. sensor gives only 3.5-3.9V
but then i read that threshold value is 2.5V


I dont know wat;s wrong..
Plz tell me wat to do.. how to take input.

[ashish_agarwal123456]

DDRC=0x00;
if(PIN==0x00)
{
//motor control
}

make it
if(PINC==0x00)

here is a page that will show you how to use avr input output.
http://elecrom.wordpress.com/2008/02...-input-output/