Alt-BEAM Archive

Message #05780



To: beam@sgiblab.sgi.com
From: Chiu-Yuan Fang chiumanfu@home.com
Date: Wed, 18 Aug 1999 12:32:14 -0700
Subject: [alt-beam] Re: MOSFET sensor thingy


Here's a message from way back...


{Terry Newton worte}
I don't know what a "capaciflector" is but here's a long distance
object/motion/ghosty detector that is simple, non critical and super
sensitive to many feet. Deceptively simple... (ascii ahead, used fixed)

(220K-?) .-------> + side ----|:|:|:---.
g |d + 9V - |
o---Rg--->|= parallel series or | test
n-jfet |s in place of existing | app
Rs of photocell or switch LED |
(1K) | ^^^ |
`------> - side ----|>|------'

Size of resistor Rs depends on what you hook it too.
On a walker I have a pair in series with the existing CdS-type
photocells, which take the place of Rs. Rg protects from charged
objects and makes a convenient antenna. Value doesn't matter much
just pick something high (mine is 220K) and solder close to the
gate, other end shaped as desired. For the J-FET I have rare TIS-58's
but almost any N channel J-FET will work. MPF102, 2n5457 etc. Drain
and source leads are usually interchangable. In my walker app the
drain goes to +, the source goes to one leg of a photocell, other
leg to a .22uF cap which a microcontroller shorts then times how
it takes to read "high" and eventually controls a microcore with
it. Best effect is how it wakes up when disturbed, even from a
distance and in the dark. If you think hard it might go off.
Hook to a battery and LED as shown (make Rs about 1K) to experiment
with antenna configurations and guage how it responds. Not for
critical steering apps, but influencing a microcore I guess the
chaotic nature of it doesn't matter much and probably helps.
For Who Knows what a microcore thinks. Cheap anyway, have fun...

Terry Newton

> Richard Caudle wrote:
>
> ------------------------------------------------------------------------------
>
> Evening all,
>
> Yet another in a long line of strange things...
>
> Today at work, I came across a circuit for detecting electrostatic fields.
> Since I have need for such a thing, I tried to build one. The only problem is
> that the required components weren't available (what else is new?). It called
> for an n-channel FET and all I could come up with was an n-channel MOSFET
> (2N7000). I got the pinout from Digi-Key and proceeded to build the circuit.
>
> Needless to say, it didn't work. So I decided that the pinout must be wrong.
> I turned it 180 degrees and it started working, but not like the description
> said it would. The closer I moved my hand to the 'antenna', the higher the
> voltage went. I put in an LED so I could watch it. It was sitting at about
> 530mV until my hand got about 10" away and it began to rise. At about 4
> inches, it went to about 1.3V and when I would touch it, it jumped to 4.8V
> (input V=5VDC).
>
> The strange thing about it: The 2N7000 is backwards! At least I think it
> is. The S (source?) pin is on the negative side of the supply and the D
> (drain?) pin is on the positive side. The gate is acting as the antenna.
> Maybe I've got the terms wrong. It's still a cool thing. I was thinking it
> could be used as a 'real' antenna for a walker or popper. It could trigger a
> Nu that operates the reverser. Something that deserves further
> investigation(IMHO).
>
> Richard Caudle
> richard@cqc.com
> Home ICQ - Frankendaddy
> ------------------------------------------------------------------------------
> Guardians of the sacred words: Nee, Ptang, and NeeWhon!

--
Chiu-Yuan Fang
chiumanfu@home.com
ICQ=5614919
http://www.geocities.com/SouthBeach/6897/beam2.html



5781 Wed, 18 Aug 1999 13:02:14 -0700 [alt-beam] Re: Contest entry (the bounty bot) beam@sgiblab.sgi.com Chiu-Yuan Fang Bob Shannon - LEM : http://www.the-nest.com/bshannon/

Darrell Johnson - Mod-Worm 1.0 : http://www.beamzine.com/contest/DJohnson/

Dennison Bertram - DiskRat : http://www.beamzine.com/contest/DBertram/
(vid coming...my fault for delay)

Kyle Davenport - hUFO : http://www.beamzine.com/contest/KDavenport/
(vid and pics coming...ditto)

Contest is closed to any more entries. I'll get those vids on-line today.

Chiu

Bob Shannon wrote:
>
> Ian Bernstein wrote:
>
> > >Ummmm I made a bot that tracks a line can I enter it
> > >too? I just want to state my objections to Ians
> > >entry. How in the hell is a bicore rolling bot an
> > >inovative form of motion? What does putting a bit of
> > >cloth on it to make it a "quicker picker upper" really
> > >have anything to do with inovative form of motion?
> > >Does it make a light show from static electricity or
> > >anything? No it just rolls around like anything else
> > >using a bicore and wheels. It is just a cheap way for
> > >Ian to try and get a prize and not contributing
> > >anything to the different types of motion.
> >
> > Your right. It's not really completely done anyways. I'd like to pull it
> > from the competition.
> > There was only like one or two entries right? Lots of good prizes for the
> > next competition!!!
>
> What about the 'bots and videos mailed directly to Chiu? Now that the
> deadline has
> passed, can we get a list of all enteries?

--
Chiu-Yuan Fang
chiumanfu@home.com
ICQ=5614919
http://www.geocities.com/SouthBeach/6897/beam2.html



5782 Wed, 18 Aug 1999 23:33:25 +0200 [alt-beam] Edge detectors arno.jansen@superconsult.nl (Arno Jansen) Just an idea I got while trying to sleep....(know what I mean???)

Okay, now... I know there are bots with obstacle avoidance/detection. So,
they will most likely not run into a wall. But, when you put them on a
table, they might fall of the edge.......probably dead.

But! (here's my little brainwave). It must be possible to make some
edge-detectors. I haven't drawn a scheme or something, but this is what I
think: It can some sort of leg. For example left front and one on the front
right side. (ascii-1)


\ /
\ / <- edge detectors
\ /
--------------
| bot |
----------------
ascii-1 (I hope this will be well viewable...)

Those legs must be stiff (not being able to bend) have some weight at their
ends (those you remove from the namiki's). When the "edge-detector" reaches
an edge, the little weight will make it drop off, so it makes contact (just
like a tactile sensor) and the bot can react and probably move backwards.

For walkers you might want to use a pressure sensor, they're not expensive
and they're small. So if you somehow manage to know when a walkers' leg is
in the air, and when it's on the surface, you can "predict" what the
difference of the value of the pressure sensor is, so whenthe leg is on the
surface and the sensor's value is equal to the value it gives when the leg
is in the air, you know, it's probably near a gap, or an edge and it could
react and move in another direction.

I am not (yet) able to try this, 'cause I'm still waiting for parts to build
my first photovore... and I haven't much spare parts yet. But if anyone
starts thinking about this concept, this mail wasn't for nothing.

So.. comments?

Arno

P.S. Or was I stupid to think I was the only one thinking of this problem???
:)

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