Alt-BEAM Archive

Message #13580



To: beam@sgiblab.sgi.com
From: Bruce Robinson Bruce_Robinson@telus.net
Date: Mon, 17 Apr 2000 13:02:35 -0700
Subject: Re: The human body and electricity


Timothy Flytch wrote:
>
> ... Your brain sends a low voltage electrical impulse that tell
> your hart to beat...

Well, ... not quite.

The brain doesn't get involved. "The heart has an inherent contractile
rhythm. That is to say, if all the nerves supplying the heart are
severed, the heart continues to generate nervous impulses causing it to
contract in a rhytmical fashion." **

The heart has a special type of muscle fibre interlaced with the regular
fibres. These fibres conduct impulses faster than the regular muscle
contracts. In effect, a contraction ripples through the heart, and sets
itself off again. Sound familiar? Like a microcore :)

The nerves that connect to the heart muscle can influence the
sensitivity of the special fibres, thus causing the heart rate to
increase (chemicals circulating in the blood, e.g., adrenaline, also
have this effect). Sounds even more like a microcore :)

The heart's normal contractions are caused by an electro-physiological
mechanism, so they can be destroyed by extremely high voltages.

A more common problem which occurs with lower voltage shocks (even
household current) is when the heart muscles are sensitized to the point
that they conduct impulses at a very high rate (fibrillation). Basically
the heart begins to vibrate so quickly that it doesn't have a chance to
move blood. Try reducing all the resistor values on a microcore by a
factor of 1000 and see what happens to the motors :)

> ... This is the bases for the one hand method (keep one hand in your
> pocket)...

Personally, I think it's safer to keep both hands in your pocket. Then
get your macho buddy to take the CRT apart. Borrow some money from him
first :)

Bruce

** Quote is from "The Physiological Basis of Physical Education", by
Fox, Bowers, and Foss.



13581 Mon, 17 Apr 2000 13:00:16 -0700 Re: i swear the circuit's correct!!! beam@sgiblab.sgi.com Bruce Robinson Hi, Evan.

> what are possible things that could make ALL the
> outputs of a microcore be HIGH at once, regardless of
> how hard i try to introduce processes into it?

1. No impulse(s) circulating.
2. See above :)

I guess you already figure that out.

The only way to introduce an impulse is to make one of the inverter
inputs high momentarily. That's what the PIC is supposed to do.

My first test was (and is) to disconnect any PIC circuits and briefly
connect an INVERTER input to Vcc using a piece of jumper wire. That
should make at least one neuron output go low, even briefly.

If that doesn't work the first time, try it with each of the other
inverter inputs in your microcore.

If THAT doesn't work, hook your jumper wire to Vcc as I suggested, not
to ground (sorry, I've done that too many times myself not to mention
it).

Got an impulse? Good. Does it go around the loop, or die somewhere?

If it dies somewhere, you might have a bad connection between the last
Nv that goes low and the one that doesn't respond. Or else you might
have an inverter input shorted to ground.

Got a circulating impulse by now? Then maybe the problem was with the
PIC. Is it connected to the right place -- the INVERTER input, not the
Nv input? And has it got the right polarity?

Don't scrap it yet, there's still hope. And don't automatically assume
the chip is fried. I've only nuked two by hooking them up wrong, and
they were both hot enough to cook an egg by the time I noticed.

Bruce



13582 Mon, 17 Apr 2000 13:19:16 -0700 RE: Deadman's stick (was: RE: Monitor Salvage) "'beam@sgiblab.sgi.com'" Wilf Rigter John's description of the "deadman's" stick is correct: the wooden dowel
acts as an insulated handle and should be held at one end with the resistor
and pin secured to the opposite end.

The CRT anode capacitance behaves just like a Leyden jar (the world's first
capacitor). The anode lead connects to a terminal on top of the CRT through
the glass envelope to the metalization on the inside and face of the CRT. A
rubber suction cup covers this connection to the CRT anode terminal. The
metalized outside of CRT is grounded to the chassis ground using contact
fingers or a spring tensioned bare wire in contact with the CRT. The CRT
capacitance filters the dc voltage on the anode generated by the horizontal
flyback transformer and rectifier assembly. The anode voltage depends on
the size of the CRT and can be as high as 30,000 Volts. The remaining charge
on the CRT anode can be quietly discharged through a >1M resistor to ground
using a well insulated "deadman's stick". Before discharging, the monitor/TV
MUST be unplugged from the AC power supply and always FIRST connect the
grounded side of the discharge resistor to a suitable place on the
chassis/frame before touching the other side of the resistor to the "hot"
terminal of the cap. For a CRT anode, the hot terminal is the metal contact
under the suctioncup on top of the CRT at the end of the anode lead. The
deadman's stick has a stiff pin on the end which can slide under the suction
cup and discharge the CRT.

regards

wilf

> -----Original Message-----
> From: John A. deVries II [SMTP:zozzles@lanl.gov]
> Sent: Monday, April 17, 2000 10:37 AM
> To: beam@sgiblab.sgi.com
> Subject: Deadman's stick (was: RE: Monitor Salvage)
>
> I seem to remember a tool that TV/radio repair types used to have or make
> for themselves called a deadman's stick. Basically, it was a stick of
> wood
> (a dowel would work) that is about a foot long with a pin stuck in one
> end. Someplace close to the pin you'd tape a 1M ohm resistor and connect
> it to the pin with some wire and then run another piece wire back up the
> stick. Of course, where you soldered on both sides of the resistor you'd
> put a fairish amount of electrical tape -- I suppose the PVC stuff they
> sell these days would work. The wire that was on your side of the
> resistor
> would be perhaps two feet long (depended on how big the equipment was that
>
> you worked on) and you'd solder an alligator clip onto it. Chances are
> you'd want to have one of those alligator clips that has the plastic
> shroud
> -- some of us can be fairly clumsy when hooking it to one side of a cap
> (which could be a pain if the other side was connected to something that
> another part of your hand touched.)
>
> Anyhow, you'd then attach the alligator clip to some part of the chassis
> that was obviously grounded or one end of some component you wished to
> discharge and you could go poking around (one hand in your pocket, as they
>
> say) to discharge capacitors and the TV tube itself (which acts as a HUGE
> capacitor -- they don't put those warning signs on for jollies and the
> charge can stay on it for many many months). When you probed a particular
>
> connection, you held it there for a while to make sure that the thingy you
>
> were discharging was really dead.
>
> Now, what I don't remember exactly is how one discharges a TV tube...
> Wilf??
>
> <----------=========---------------K
> pin resistor alligator clip
>
>
> Zoz
> Someone who has picked up a live monitor chassis and still remembers how
> much his arm hurt afterwards. Thank God it was low current!!!



13583 Mon, 17 Apr 2000 17:03:32 -0400 Re: ...notes from the electronically challenged.... beam@sgiblab.sgi.com Richard Weait At 11:26 AM 4/17/00 -0500, Jim Scolman wrote:

[snips throughout]

>Good morning All... I powered the circuit with six, 1.5 volt
>batteries. My meter showed the batteries as giving a solid 5V of power.

Question: Six 1.5V batteries in series should give 9V. What's up?
Are they in series parallel? Has the 9V supply 'cooked' the chip,
and drawn so much current that only 5V is seen? Many chip families
will not appreciate the 9V supply.

> Question #1. With the circuit powered and both motors turning, I
>tried to hold one of the motors, but the torque

See Wilf's trouble-shooting advice.

> Question #2. My solar cell, SC3766-1, produces a solid 5V, but it
>will not turn even ONE motor, connected directly

When things are working with the battery or power supply you
can get ready to switch to solar power. You'll probably need
some variation of a SolarEngine at that point. The SolarEngine
will 'save up' solar energy as charge in a capacitor over time.
When the SolarEngine triggers, the charge from the capacitor
runs the circuit.

>soon. Thanks for the help and answers.....JWS.

Cheers,

Richard.

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