IR Emitter / Receiver / Detectors ... need help

[micro571]

Hi,

My goal is to use IR sensors / recievers in a simple setup, using a LM393 comparator ... to create a simple line following robot.

I can't seem to get them to work ... what am I doing wrong?

I've got the emitter (very similar to a regular LED), hooked up to a 5V power source with a resistor.

The reciever is a 3-pin device. The pins are hooked up matching pictures / diagrams I found on the net. 5V, Ground, Output Pin

On the output pin, I'm trying to get a voltage reading, but the reading doesn't change at all based on whether the IR Emitter is on or off.

I've also got an IR detector (2 pins, very similar to the emitter). I can't get a changing reading off of that device either.

What am I missing? A lot of the IR projects on the net use microcontrollers. Is it even possible to work with IR using strictly analog components like I'm trying to do?

Thanks.

Jon
MICRO571

 

[Nigel Goodwin]

What am I missing? A lot of the IR projects on the net use microcontrollers. Is it even possible to work with IR using strictly analog components like I'm trying to do?

Yes it is, it's easily possible, there are many line follower designs using simple analogue systems.

It sounds like you are possibly connecting something up wrongly, or using inappropriate components. It obviously doesn't help when you can't see the light from the emitters, it might be a good idea to use visible light LED's instead?.

 

[JFDuval]

Hello!

I'm pretty sure I know what is the problem with your 3-pin receiver. You didn't mention anywhere that you used a decoupling capacitor on the output. Whit those receiver, it's a must. Read the datasheet, you will find an hook-up diagram.

For the IR light, you can see it if you have a webcam or a camcorder. The CCd sensor is sensible to the infrared region.

Hope this help,

 

[The Real MicroMan]

I've had a lot of experiance with IR circuits. Your 3 pin device might be one that needs 40khz to activate. it's called a IR detector decoder, very common. you 2 wire device is a current based device. were the current will change based on how much light is present. that change in signal prob has to be amplified in order for you to see it.

 

[micro571]

The 40Khz, is that the frequency of the IR light ??

 

[JFDuval]

Hello!

The frequency depends of the module. You can have 33, 38, 40, 56, etc ones. You need to pulse the IR led at this frequency in order to make it work.