Alt-BEAM Archive

Message #07293



To: beam@sgiblab.sgi.com
From: Senior kyled@cruzers.com
Date: Tue, 02 Nov 1999 15:52:32 -0700
Subject: [alt-beam] Re: directional antenna?


Evan Dudzik wrote:
>
> does anyone have any ideas on how to build a
> unidirectional antenna? this would be great for homing
> in on RF signals... otherwise, i have another idea.

If there is something that won't let radio waves pass through it you
could cover all but one part of your antenna with it, effectively
"aiming" it.

> take three antennas, and place one in the center of
> the bot... take the next two and place them at the
> left and right sides of the bot. now, have a beacon
> set up that transmits signals... it just has to
> transmit a signal, wait for like a second, and then
> trasnmit another... the robot will have its central
> antenna on at all times, waiting for that first
> signal. when it recieves it, it turns on the other
> two recieving antennas... when the signal comes, it
> will reach one antenna BEFORE the other because that
> antenna is closer. The difference between times would
> be REALLY short, so the bot would have to have some
> quick detecting circuitry (TTL... isnt that really
> fast? fast enough?) this whole thing is kinda how our
> ears work, sound reaches one side before the other.
> any ideas on circuitry? or whether this thing would
> even work? it would be good to help a bot home in on
> its charging station... or other uses. anyway,
> thanks.

This is called triangulation because there are three points: Becaon, and
two on the bot. You only need two on the bot, just have one listening
and then it turns the other one on or both on all the time or whatever
you like. It's been done. Steven Bolt did this osrt of thing with sound
and microphones at:
http://www.xs4all.nl/~sbolt by the way, anyone heard from him lately?
or chiu!!!!

So, yes, this is very doable. Search around, maybe you can find a kit or
schematics.

Kyle



7294 Tue, 02 Nov 1993 19:27:14 -0600 [alt-beam] solar PSHead motor driver question beam@sgiblab.sgi.com SG ok, the parts finally came in, i replaced the old 74HC240 for a DigiKey one,
and the old 1381 "J" with an "L"

the Fled fired up just fine (under INTENSE light btw)
but nothing from the motor outputs to even fire up an LED.

so.. some of you suggested a motor driver or H-Bridge.

i hooked up a 74ALS245 to the motor and:
now not even the FLED goes off.

correct me if i'm wrong, but a motor driver has to have its + and -
connected directly to the power source....
therefore it is draining the cell before the cell has a chance to charge
the capacitor because it (the driver) is not turned on by the trigger.
I am sure i am wrong and that there is a proper place to hook up the power
to a motor driver on this solar circuit.

any help would be great!
-Sparky

Home