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[DPRG] Re: can i use a bulb mounted on an object for identification?

Subject: [DPRG] Re: can i use a bulb mounted on an object for identification?
From: Brian Scearce bls at best.com
Date: Thu May 18 11:27:32 CDT 2000

Raymond writes:
> Since the Handyboard use the L293D H-bridge chip to generate the
> PWM signals to the dc motor but the peak current gives out is just
> 1.2A, since the common toy motors sometimes draws up to about 3A.
> This causes the handyboard to reset and stop the motors. I have
> just solved this problem by isolated the motors with another separate
> power supply. So, the motors work ok now.

Using a separate supply for your motors will stop the voltage sag
and noise that can reset your microcontroller, but the 1.2A limit
of the L293D still stands.  If you're running 3A (or 6A?  3A per
motor?) through it, you will probably burn it out.

> As some of you taught me that I can hack the wheels and the light
> emitter and receivers but I don't know how I can interface theses
> to the i/o ports of my controller board and what is the operation
> of the receivers?

_Mobile Robots_ has some descriptions of how to do this, and even
Handyboard-based code.  The basic idea is to measure the actual
speeds of the motors (by counting transitions on the detector) and
adding or subtracting from the PWM if the actual speed differs from
the desired speed.

If you don't have _Mobile Robots: Inspiration to Implementation_
by Flynn and Jones, I would recommend that you get it!  It's a
great book.


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