Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: xodiac on March 03, 2009, 05:46:50 PM

Title: IR LEDs when used as sensors
Post by: xodiac on March 03, 2009, 05:46:50 PM

I wanted to create a sensor for my robot so that it detects objects in front of it (1-5cm) and then reverse.

For the object sensing, I have chosen to use 2 IR LEDs, one for transmitting and the other one for recieving as described in http://www.ikalogic.com/ir_prox_sensors.php (http://www.ikalogic.com/ir_prox_sensors.php)

I wanted to know a few things before ordering the IR LEDs:

Does the wavelength really matter when ordering them? as long as both are of the same type, will there be any problem? If so, what wavelength should I go for?

Title: Re: IR LEDs when used as sensors
Post by: superchiku on March 03, 2009, 09:33:50 PM

emitter detector pair must be rated same...

Title: Re: IR LEDs when used as sensors
Post by: TrickyNekro on March 04, 2009, 05:08:28 AM

They should match to do the trick, but close enough wave lengths work...
You can make this circuit a very good sensor if you want to place so personal effort in it...
You can avoid ambient light from being detected with a modulation trick...
For this the only thing you want to add is a high pass filter on the output of the detector
right BEFORE the op amp and of course generate a modulating signal at the output of the
emitter led...
With this method, you are gonna have a sensor like TSOP17 series and so...
using and being able to program tiny microcontrollers like ATtiny13 will do the trick for sure....
they will help you debug the circuit and place a digital output....

The only thing that really halts myself from doing that is the existence of premade ICs for that...
Like the one I wrote above...

Best Regards,
 Lefteris
Greece

Title: Re: IR LEDs when used as sensors
Post by: xodiac on March 04, 2009, 12:08:05 PM

Quote from: TrickyNekro on March 04, 2009, 05:08:28 AM

With this method, you are gonna have a sensor like TSOP17 series and so...
using and being able to program tiny microcontrollers like ATtiny13 will do the trick for sure....
they will help you debug the circuit and place a digital output....

The only thing that really halts myself from doing that is the existence of premade ICs for that...
Like the one I wrote above...

Best Regards,
 Lefteris
Greece

I am trying to make a fully analogue circuit, without digital outputs.

Title: Re: IR LEDs when used as sensors
Post by: superchiku on March 04, 2009, 12:18:36 PM

thats is bad then...comparator  have to be used if u wish to steer the bot

Title: Re: IR LEDs when used as sensors
Post by: TrickyNekro on March 06, 2009, 04:22:35 PM

Without, filtering the data, you 're gonna have problems with environmental noise....
Better if you task a separate microcontroller to do this, no matter what the output is...

Title: Re: IR LEDs when used as sensors
Post by: Soeren on March 06, 2009, 10:26:40 PM

Hi,

Quote from: xodiac on March 04, 2009, 12:08:05 PM

I am trying to make a fully analogue circuit, without digital outputs.

Does that mean that you want an analog output rising (or falling) with distance?