Author Topic: Following A Light  (Read 1908 times)

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Offline MegaLaDonTopic starter

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Following A Light
« on: July 29, 2012, 07:29:41 PM »
I am new to robotics and am looking for some advice. What I want to do is make my robot follow a light source (like a flashlight). How would I go about doing this?

Offline newInRobotics

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Re: Following A Light
« Reply #1 on: July 30, 2012, 03:08:28 AM »
You probably want to read and complete (actually build) the famous $50 Robot tutorial :)
"Computer games don't affect kids; I mean if Pac-Man affected us as kids, we'd all be running around in darkened rooms, munching magic pills and listening to repetitive electronic music." - Kristian W

Offline greywanderer012345

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Re: Following A Light
« Reply #2 on: August 10, 2012, 04:20:38 PM »
When I made the $50 robot, I put the light sensors underneath the chassis so that it doesnt chase lights in the room. Instead, it chases light on the ground, like a flashlight. It works, but not great in a lit room. I think some photoresistors act differently for certain frequencies of light. Im thinking about looking into this to make a bot that follows a red laser specifically. Hope this helps.

Offline Soeren

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Re: Following A Light
« Reply #3 on: August 10, 2012, 11:06:26 PM »
Hi,

I think some photoresistors act differently for certain frequencies of light. Im thinking about looking into this to make a bot that follows a red laser specifically. Hope this helps.
Photoresistors (CdS) all have a fairly wide spectre and you won't get that much difference by changing them. If you add a color filter over any photoresistor, you can dampen its sensitivity to other colors, well enough to get it to differentiate eg. a red and a green LASER, but white light contains both red and green, so a filter letting eg. red through will also let the red part of white light through.

Pulsing the LASER will make it possible to exclude all other light - color won't.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline greywanderer012345

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Re: Following A Light
« Reply #4 on: August 11, 2012, 10:13:46 PM »

Photoresistors (CdS) all have a fairly wide spectre and you won't get that much difference by changing them. If you add a color filter over any photoresistor, you can dampen its sensitivity to other colors, well enough to get it to differentiate eg. a red and a green LASER, but white light contains both red and green, so a filter letting eg. red through will also let the red part of white light through.

Pulsing the LASER will make it possible to exclude all other light - color won't.



Have you seen the "Follow Me Thomas" toy?
http://www.toysrus.com/product/index.jsp?productId=4048063

My niece got one of these, and it's the reason I wanted to try to get my bot to follow a laser. Instead of a laser(can't give those to 3 year olds) this toy comes with a red flashlight, and the train follows the circle where the beam is shone. I believe there is a sensor behind each bumper. I figured it used photo-resistors specific to red light. Do you think it just uses regular photo-resistors and covers them with transparent red plastic? The toy works very well, even following the light on red carpet or wooden floors and in brightly lit rooms.

Offline MegaLaDonTopic starter

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Re: Following A Light
« Reply #5 on: August 12, 2012, 04:06:29 PM »
All of this looks very interesting. I will certainly look into it. Thank you everyone for the input.

Offline Soeren

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Re: Following A Light
« Reply #6 on: August 19, 2012, 09:39:02 AM »
Hi,

Have you seen the "Follow Me Thomas" toy?
http://www.toysrus.com/product/index.jsp?productId=4048063

Now I have, thanks :)


My niece got one of these, and it's the reason I wanted to try to get my bot to follow a laser. Instead of a laser(can't give those to 3 year olds) this toy comes with a red flashlight, and the train follows the circle where the beam is shone. I believe there is a sensor behind each bumper. I figured it used photo-resistors specific to red light. Do you think it just uses regular photo-resistors and covers them with transparent red plastic? The toy works very well, even following the light on red carpet or wooden floors and in brightly lit rooms.

Either color filters or they just use them plain. If there's a much larger amount of light where it shines, it doesn't need to be color sensitive. You could try with a bright white flashlight (it should work anyway, as there's red in the white) and with a green filter in front of the white flashlight - if green light doesn't work, it indicates red color filters. For testing, any piece of (resonably green) clear plastic should do.
Perhaps you can see it with your naked eye, as red filters would cover the distinct pattern of the CdS resistor.

To follow a LASER dot, you might wanna decollimate the LASER to a wider spot, to make it easier to follow.
Most pointers have a notch in the LASER head where a small coin or similar fits. If it's not sealed with glue or thread lock, it can be twisted/turned to collimate (parallelize the beam). When I use a pointer for such stuff, I usually make the spot as wide as around 5..10cm in diameter at a ~1m distance from the head.

Modulating the LASER beam and making the sensors ignore light from unmodulate sources will make it far better behaven.
To modulate it and keeping the switching speed resonably, set the low part to a point where it is just "lasing" (beyond that current, the light will just be like a weak red LED) and set the high part to te max. current it uses, with the voltage and internal resistance of the button cells it normally uses.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline arunyogesh46

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Re: Following A Light
« Reply #7 on: September 05, 2012, 09:33:14 AM »
I have a solution for all your doubts. It is very easy to make a light following robot without using microcontroller.

The step by step instructions to develop this robot is given in the below link. I made one from the details given in this website. It really works... try it... I hope you too will get the output...

http://www.roboticsbible.com/light-following-robot-without-using-microcontroller.html

Offline Adrianlstaton

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Re: Following A Light
« Reply #8 on: May 20, 2013, 01:35:44 PM »
I have a solution for all your doubts. It is very easy to make a light following robot without using microcontroller.

The step by step instructions to develop this robot is given in the below link. I made one from the details given in this website. It really works... try it... I hope you too will get the output...

http://www.roboticsbible.com/light-following-robot-without-using-microcontroller.html



Yea Its Really work. It is very Helpful for all of you. Try this.

 


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