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Electronics => Electronics => Topic started by: hardi on April 25, 2011, 06:08:19 PM

Title: need advice to build micromouse robot
Post by: hardi on April 25, 2011, 06:08:19 PM
I'm beginner, i want to build my first micromouse robot..
I had a problem on the sensor, the distance is not more than 3 cm..
I use IR LED and photodioda..
what should i do to create a sensor with a greater distance?

this is my schematic,i need help ???
Title: Re: need advice to build micromouse robot
Post by: Soeren on April 25, 2011, 07:21:56 PM
Hi,

I had a problem on the sensor, the distance is not more than 3 cm..
I use IR LED and photodioda..
what should i do to create a sensor with a greater distance?
How much distance do you need?

Using a photo transistor instead of the photo diode will help a lot, but if you need even more than what that can do, you need to use modulated IR light and then an integrated IR receiver is best.

A Sharp IR distance sensor is a more expensive type, but it gives you the distance, rather than just on/off.

Is this for wall detection?
Title: Re: need advice to build micromouse robot
Post by: hardi on April 26, 2011, 02:10:46 AM
hi,thanks for thx answer..

yes,this is for wall detection..
I've been using a phototransistor, and the result is not different from using the photo diode..
yeah, I want to use sharp IR, but it's too expensive..
the distance that i want is 6 cm,i want use ADC for ATMEGA32..

whether there is an additional circuit for this sensor to reach the distance that I want?
Title: Re: need advice to build micromouse robot
Post by: Soeren on April 26, 2011, 05:55:01 AM
Hi,

I've been using a phototransistor, and the result is not different from using the photo diode..
That sounds strange.


the distance that i want is 6 cm,i want use ADC for ATMEGA32..

whether there is an additional circuit for this sensor to reach the distance that I want?
First of all, make sure the IR LED has a wavelength that matches the peak wavelength of the detector - i.e. if the peak wavelength of the receiver is eg. 930nm then the LED should be 930nm as well (a difference of ~10nm will be OK). You find those specs in their respective datasheets.

Reduce RSENL1 from 330 Ohm to 68 Ohm. This gives a fourfold rise in LED current, so should approximately give twice the range of what you get with the 330 Ohm.

Experiment with RSENP1 to find the best value. You could use a resistor of 5k in series with a trimming potentiometer of 50k to 100k to dial in the best value, measuring the output with a voltmeter, while moving a "target" back and forth in front of the setup.
Title: Re: need advice to build micromouse robot
Post by: hardi on April 26, 2011, 08:02:11 AM
thanks for the advice, I'll try it :)
Title: Re: need advice to build micromouse robot
Post by: TrickyNekro on April 28, 2011, 03:03:14 AM
Just to note that the capacitor on the output is not very wise...

If you really want a low pass filter at the output, software it ;)
Title: Re: need advice to build micromouse robot
Post by: hardi on April 28, 2011, 04:16:20 AM
with software?
that's sounds good..

can you explain it?
 ???
Title: Re: need advice to build micromouse robot
Post by: Soeren on April 28, 2011, 01:28:40 PM
Hi,

Just to note that the capacitor on the output is not very wise...
It's plenty wise.


If you really want a low pass filter at the output, software it ;)
Strange, you want to replace a well proven and cheap solution with a huge sw overhead?
Did you ever scope such an output?

Keep the cap, I say.
Title: Re: need advice to build micromouse robot
Post by: Soeren on April 28, 2011, 01:29:40 PM
Hi,

thanks for the advice, I'll try it :)
So, how did it go down?
Title: Re: need advice to build micromouse robot
Post by: The arctic wolf on April 28, 2011, 03:58:09 PM
Hello everyone,
I agree with Soeren about the capacitor, it's a good solution.
About the IR diode, what I usually do in order to get the best out of them is as following:
1. I find out from the data sheet or by measuring what is the voltage accross the diode when it's fully open(when it's in "on" state).
2. I find out from the data sheet what is the maximum recomended current the LED can handle(usually apears as Imax in the charts).
3. I do the following math(old proven ohms law :)   )   :
(Vcc-Vopen)/Imax=R.

Where  Vcc is the voltage of the battery(or other voltage source), Vopen is the voltage accross the diode mentioned in paragraph 1, and R is the value of the resistor to be connected in series with the LED.
4. In reality I use a resistor with a little bigger value then I recieved from the previous calculation in order to be on the safe side.


Hope it helps :).

Now I would like to ask a little stupid question, what is a micromouse robot??



Andrei.
Title: Re: need advice to build micromouse robot
Post by: Soeren on April 28, 2011, 04:17:46 PM
Hi,

[...] what is a micromouse robot??
Now I bet you wished you had just done this (http://www.google.dk/search?q=micromouse&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a)  :P
Title: Re: need advice to build micromouse robot
Post by: knossos on April 28, 2011, 04:22:23 PM
It's a small maze solving robot.  For example this recent article (http://hackaday.com/2011/04/28/the-concepts-behind-robotic-maze-solving/) on HaD (http://hackaday.com).  Also from Admin's youtube:

MicroMouse Robot Competition (http://www.youtube.com/watch?v=bproY7G2t4o&NR=1#)

Title: Re: need advice to build micromouse robot
Post by: The arctic wolf on April 28, 2011, 04:56:28 PM
Sorry :-[  .
And thanks.