Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: aruna1 on February 12, 2010, 01:39:05 PM

Title: which sensor to use?
Post by: aruna1 on February 12, 2010, 01:39:05 PM

Hi '
I need to build a white line follower, and my question is about the sensor
sholud i use
White LED + LDR
or
38khz IR + TSOP1738 sensor


i know LED+LDR pair will get affected by ambient light and TSOP is good for noise immunity
my problem is wont TSOP sensor generate false signals due to sudden change in ambient IR (sudden change in sun light)?

to get maximum efficiency which sensor should i use
thanks

Title: Re: which sensor to use?
Post by: Pratheek on February 13, 2010, 04:44:42 AM

I've written a tutorial on choosing sensors for line followers at http://www.societyofrobots.com/member_tutorials/node/353 (http://www.societyofrobots.com/member_tutorials/node/353).
I think you will not be able to use the TSOP sensors for line following with much success. From my experience they are too sensitive - they will get triggered even by the little IR light that gets reflected from the black surface and the robot will think the sensor is on the line!

Title: Re: which sensor to use?
Post by: aruna1 on February 13, 2010, 06:27:27 AM

Quote from: Pratheek on February 13, 2010, 04:44:42 AM

I've written a tutorial on choosing sensors for line followers at http://www.societyofrobots.com/member_tutorials/node/353 (http://www.societyofrobots.com/member_tutorials/node/353).
I think you will not be able to use the TSOP sensors for line following with much success. From my experience they are too sensitive - they will get triggered even by the little IR light that gets reflected from the black surface and the robot will think the sensor is on the line!

well i read your article before,but problem i have is will ambient light saturate sensors (IR sensors-photodiodes)

Title: Re: which sensor to use?
Post by: Soeren on February 13, 2010, 08:51:00 PM

Hi,

Quote from: aruna1 on February 12, 2010, 01:39:05 PM

[...] to get maximum efficiency which sensor should i use

You can modulate an LED and then have a filter circuit in your preamp for the photo device you're using (photo diode/transistor). That way you can ignore the occasional sun beam, but you need to keep the sensors shaded from direct light, or make a light controlled bias arrangement for the input stage, as any strong light source will otherwise swamp the photo device and render it blind to your wanted signal.

Title: Re: which sensor to use?
Post by: aruna1 on February 13, 2010, 09:56:49 PM

Quote from: Soeren on February 13, 2010, 08:51:00 PM

or make a light controlled bias arrangement for the input stage, as any strong light source will otherwise swamp the photo device and render it blind to your wanted signal.

what do you mean by this

Title: Re: which sensor to use?
Post by: Soeren on February 14, 2010, 09:09:21 AM

Hi,

More light on the photodevice can be biased by more current through it, to keep a "balanced" output.
This needs to be covering only DC and slow variations of course, as the modulated signal should change the output form the setup.

Title: Re: which sensor to use?
Post by: aruna1 on February 14, 2010, 09:36:42 AM

Quote from: Soeren on February 14, 2010, 09:09:21 AM

Hi,

More light on the photodevice can be biased by more current through it, to keep a "balanced" output.
This needs to be covering only DC and slow variations of course, as the modulated signal should change the output form the setup.

still didnt get it.

Title: Re: which sensor to use?
Post by: aruna1 on February 17, 2010, 06:18:26 PM

hi, i want to build fast line follower that will work in bright sunlight.i will not use ldr as they are slow.now my options are simple IR pair or tsop sensors.bt as pratheek mentioned tsop sensors are too sensitive,that leaves only ir tx rx pair.but as sun light has too much ir sensors will go blind. can some one give a suggession? my conditions are fast line follower under bright sunlight.thanks