Alt-BEAM Archive

Message #06093



To: alt-beam@egroups.com
From: Mark Cowart mcowart@warrior.mgc.peachnet.edu
Date: Wed, 15 Sep 1999 17:46:27 -0400
Subject: [alt-beam] Floppy drive read/write heads


I'm new to "Beam-tech" & to this list. I've tried to read as many of the
previously posted messages but with about 7000 of them.......
Has anyone done any work with floppy drives? I seem to accumulate bad
drives @ work. The head tracking motor was of initial interest but I later
found out that they required the drive case to operate. The motor has no
back bushing to support the shaft. Support is built into the drive frame.
After dismantling a few drives, the read/write heads begs to be use and
abused by someone with no regard for their original purpose. What I was
thinking was some sort of current driven magnetic feedback sensor. Maybe to
locate or avoid objects, or to monitor other bot components through current
sensing. Could it be introduced into a RC timing circuit to make the
circuit variable?

I'll be experimenting with a few of these concepts. So, if anyone has any
ideas I would like to hear from you.

Thanks
Mark C.
Mark Cowart (912) 934-3319
PC Support Spec. IV
Computer
Services http://www.mgc.peachnet.edu/compserv/index.htm
Middle Georgia College
Cochran, GA 31014



6094 Wed, 15 Sep 1999 19:02:07 -0400 [alt-beam] (Semi-BEAM) Dung-Beetle Robot kit Beam "Sathe Dilip" For the labor day, I drove to New Jersey. On my way I stopped at the
Edmund Scientific shop. They had one of these kits (returned by someone
- box said missing parts, As-Is; but on checking I didn't find anything
missing) going cheap. So I picked it up & built it over last week end.
This is a brief report.

The kit (made by Tamiya) has all the parts including a dual motor
(Mabuchi) dual gearbox (sheet metal + plastic gears all in one unit),
wheels, battery holder (no batteries :-), & a prebuilt IR reflection
detector board. There is a plastic dung ball that you have to assemble
with a little weight to keep the ball from free rolling.

On assembling, the robot looks more like a fork lift with the board
sitting on the fork (but this is the rear end). There is an IR LED & a
IR detector diode to be assembled in a neat pre-focussed assy. In
operation, you place the ball next to the robot & turn it on (3 AA cells
- I haven't checked the drain yet). The left motor is on and the robot
turns clockwise. When the IR beam is reflected by the ball, the right
motor turns on (left turns off) to move the bot anti clock wise & a
plastic arm pushes the ball till the reflection is missed. Now again
the left motor takes over. This motion is similar to the arc-ed
progress of a photovore. In short the bot is supposed to keep playing
with the ball.

I found that the IR reflection was being spotted at an angle to the
front direction (tubular structure of the sensor). The bot is also
sensitive to other light sources. When the ball rolled to a position
that was somewhat away, it did a couple of circles around itself & then
picked-up on the light coming from the next room & started moving in
that direction. Then it caught a reflection from my foot & turned
towards me (& got stuck at the toes). May be some tuning will help (the
IR assy can be turned up/down/left/right to some extent). The IR diode
(detector) has a built in filter but I am going to add some (darkened
color negative film) more to see if that helps.

The instructions are in Japanese but with very clear sketches of the
assembly sequence (If you have assembled some IKEA furniture, you will
know what I mean). At the end, there are a few english sentences
explaining the operation & limitations (yes it says it will be affected
by other light sources & won't work well near walls & reflective
surfaces). Assembly does not require soldering.

I looked on their (Edmund) shelves & found that they now have these on
sale for $ 30. Original sticker said $ 84 but it looks like with the
OWI kits offering more interesting robots at lesser prices, they could
not have sold these dung beetles for that price. I could not find the
Tamiya kits (they had many) in their new catalog. So if you are
interested, call them & see if the "sale" price applies to mail order.
(in case you don't already know, their website is edsci.com. {& the
usual disclaimer - I don't have any connection with them})

Dilip
--



6095 Wed, 15 Sep 1999 18:19:25 -0600 [alt-beam] Re: hextiles "Hyndman" >where can i find some hextile boards so i can construct a BEAM >ant on it

Hextile boards are not something that are very common. Basically you haveto
spend a lot of money and a bit of time getting them made by a PCB
manufacturer. VERY few people have hextiles, the only person besides Mark
T. I know that has them is Dave Hrynkiw. He might know if a bunch of them
are being made, and if you can chip in some $$$ for some. But don't ask him
for his hextiles.
#2
You can build a "beam ant" w/o hextiles
Devin Hyndman

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