Alt-BEAM Archive

Message #11279



To: beam@sgiblab.sgi.com
From: CIRCITZ@aol.com
Date: Thu, 2 Mar 2000 19:22:35 EST
Subject: [alt-beam] Power mirror motors


I was just driving and had to adjust my power mirrors, when it hit me, would
motors like this be good use for BEAM??? Anybody ever use them, or would they
just not be good enough to use, You could probably pick something like them
up at the car scrap yard really cheap...Just a thought, and if somebody has
tried it let me know how well they work.
Dan



11280 Thu, 2 Mar 2000 19:37:25 EST [alt-beam] Re: Nice stryder! beam@sgiblab.sgi.com Bumper314@aol.com In a message dated 3/2/00 5:17:11 PM Mountain Standard Time,
dave@solarbotics.com writes:

> Nope. Actually, I have the backup function installed, but no tactile
> switches...yet. But no optic sensors.

Still a beautiful creature. I was wondering where you plan to get your
hextiles made (assuming that you will sell them eventually) and when your
projected date for their availablity is.

> It's mostly on BEAM-ONLINE already. Ian built a Stryder Jr. too, but his
> doesn't have the "pace-maker". I think there's better ways, but the way I
> did it (which worked) is to set up a single pair of '240 gates in
suspended
> bicore mode, run the outputs to each of the master bicores inputs thru
> resistors near the master oscillator value. So there's 4 resistors coming
> off the 240; two to the front left master, and two to the front right
> master. Do that help?

Very clear

> You're asking _ME_ after I admit I toasted mine?!? Sure, I'll tell you how
> to kill them! ;> (as a rule trickle charge at ~15mA is VERY safe)

that will be a very useful hextile to make. battery chargers....



11281 Thu, 02 Mar 2000 16:45:38 -0800 [alt-beam] Re: Photovore Field of Vision beam@sgiblab.sgi.com Bruce Robinson Flaming Headphones wrote:
>
>> a) make sure overhead light doesn't shine directly on the
>> photodiodes (it often overwhelms them).
>
> So even sunlight would overwhelm them, eh? So how much/what sort of
> shielding would one use for this?

The idea is to eliminate light sources that don't actually contribute to
the direction-seeking behaviour. The greater the difference in light
levels striking the "eyes" the better the response. Since the brightest
sources are usually overhead (room lights, sun), unless your robot is a
climber of flyer, these lights do nothing but interfere with the light
seeking sensitivity.

You can use card stock over the eyes, recess the eyes (hmm, wonder why
we have eye sockets), or, as many builders do, wrap the eyes in heat
shrink tubing.

>> > b) turn them so they are not pointing parallel to each other. This
>> will make your robot lock onto a bright light source more easily.
>
> OK, so instead of having them point like....
>
> V|-----|V
>
> Where the open ends of the V's are the radiant sensetive areas of the
> photodiode and the part in the middle is the rest of the bot
>
> ....You'd want them to point away from each other like
>
> _| |-----| |_
>

Yes, but you want some overlap in the field of vision. The idea of the
angle is to cause a differential in light intensity if the eyes are even
a little off target. Turning the head slightly with this arrangement
causes one eye to receive light more directly, and the other eye to
receive it less directly. If the eyes are exactly parallel as in your
first diagram, they can be turned a considerable distance off target and
still receive equal amounts of light.

Bruce



11282 Thu, 02 Mar 2000 16:47:02 -0800 [alt-beam] Re: photoresistors beam@sgiblab.sgi.com Bruce Robinson
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William Cox wrote:
>
> Does any body have a schematic for a phototropic head
> or ant that uses photoresistors instead of diodes?

Here's one that has worked well for me. The photoresistors are the ones
to the right of the 1 meg resistors.

You'll need a slow oscillator of some sort to generate pulses for it ...
easy enough to make one from a Schmitt inverter.

In operation:

- a pulse causes two parallel Nv's to go active simultaneously.
Since the two outputs feed two sides of the head motor, the
head won't move.

- the photoresistors have a much lower resistance than the 1 meg
resistors, so they shorten the usual Nv delays considerably. With
different amounts of light striking the photoresistors, the Nv on
the brighter side will time out more quickly and go inactive.

- this will immediately start the head moving, until the slower Nv
times out.

- In order to make the motor run longer, the photoresistors are
connected via diodes to the opposing Nv outputs. This means
when the faster Nv times out, it effectively takes the
photoresistor out of the slower Nv. This slows the Nv right
down.

- Each pulse from the oscillator moves the head a little.

- The effect is to move the head in short bursts until the
resistance in the photoresistors is balanced.

Point the photoresistors slightly away from each other (i.e., not
parallel) and shield them from overhead light. You will also want to
have well matched phtotresistors. The circuit responds very nicely, but
is highly sensitive to anything that unbalances the circuit.

Note that you can't feed a common H-bridge with this circuit, as it will
turn on both sides at once & fry the bridge. With a low current motor,
you could use a 74HC245 to drive the head; or try one of Wilf's
"smokeless" bridges on the Beam Heretics site (Rigter Archive). I
believe Wilf also created a similar circuit to this one which used a
single chip to provide some limited head driving capability.

Enjoy,
Bruce

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11283 Thu, 2 Mar 2000 20:06:05 -0500 beambotix relations Mike Kulesza
>
>
> Anyone want to trade links between your site and beambotix?????
> ______________________________________________________
>


11284 Thu, 2 Mar 2000 20:30:29 -0500 [alt-beam] HPV BaseBoards Pix "BEAM" "Richard Caudle"
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Evening BEAM cats!

If anyone's interested in seeing the HPV boards, my BEAM page has a pic of =
them and a 9V battery (for reference). There's also a pic on the Buy Some =
Bugs page of an HPV (sans solar cells). Big Manly Motors. No more whimpy =
PhotoVores!

Richard Caudle
www.geocities.com/frankenddy/BEAM.html
Home ICQ - Frankendaddy

Guardians of the sacred words: Nee, Ptang, and NeeWhon! =



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>
Evening BEAM cats!
 

If anyone's interested in seeing=
the HPV =

boards, my BEAM page has a pic of them and a 9V battery (for reference).&nb=
sp; =

There's also a pic on the
href=3D"Buy">http://www.geocities.com/frankendaddy/BuySomeBugs.html">Buy Some Bu=
gs =

page of an HPV (sans solar cells).  Big Manly Motors.  No more wh=
impy =

PhotoVores!

 


 

Guardians of the sacred words: N=
ee, =

Ptang, and NeeWhon!         =





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