Alt-BEAM Archive

Message #06029



To: beam@sgiblab.sgi.com
From: "Ben Hitchcock" beh01@uow.edu.au
Date: Sat, 11 Sep 1999 17:25:54 +0000
Subject: [alt-beam] Re: Spark igniter


>Hi
>Today me and my friend built a potato cannon. For those of you that don't
>know what a potato cannon is it's a large gun made out of PVC pipe that
>shoots out potatos and uses hair spray for fuel. The igniter we used is
>from outdoor grills and when the button is pressed a rather large shock
>is produced (up to about 3/8"). I am curious where all the electricity
>comes from because there are no batteries or anything. Anyone know how
>these work? I know it's not really beam but it may an spark an idea for a
>new preditor bot that shocks it's prey (already been discussed) or
>something. Don't get get any ideas about mounting the gun on your human
>seeking head though (interesting idea, any thoughts on how to make a head
>seek humans?).

The sparking device contains a piezoelectric material, a spring, and a
weight. That's pretty much it. The way a piezoelectric material works is
that it produces a voltage when you compress it, and also it will compress
when you apply a voltage. So it works both ways. You may have seen a
piezoelectric speaker already - they are those little flat brass speakers
that you find inside cheap toys and greeting cards.

Anyway, the way the sparker works is that when you press the button, the
spring compresses, until the weight gets past the trigger part - and then
the spring forces the weight to slam against the piezo material. This
produces the voltage that you can see (and feel, if you're the recipient!).
It produces a couple of thousand volts, but the duration is very short, and
the current available is absolutely minimal. I would still be reasonably
careful not to get too many shocks though - a shock like that if it occurs
across your chest can cause your heart to lose it's rhythm. There is a
critical part of the heart's rhythm (about 10% of a full cycle) where if you
get a shock, you can cause the heart to lose its rhythm. This is why at BHP
(Where I work) EVERY shock must be reported and your heart tested. Even
little 32V shocks should be reported.

So, I guess the moral is don't stick the terminals across your chest.

PS. With the cannon, did you have a T-piece at the bottom to create a
bigger expansion area, or did you only use the one straight piece of tube?

Ben Hitchcock



6030 Sat, 11 Sep 1999 00:31:16 -0700 [alt-beam] power_smart_head fest rained out beam@sgiblab.sgi.com Sean Rigter Howdie all,

After chewing up precious hours of freetime prototyping the latest versio=
ns of
the PS head, I confess that I'm having problems with repeatability of res=
ults.
Layout appears to be critical and a "real" head behaves quite different f=
rom
some of the simulated protoboard version. So apologies to all and a prom=
ise to
iron out the wrinkles asap. Till then either build Darrell's version or w=
ait
while I work out a more stable design for an improved PS head version bef=
ore I
can suggest that anyone attempts to build it.

So don't worry : be happy

wilf

Wilf Rigter wrote:

> Hi Bumper,
>
> What do you think of a little "t=EAte-=E0-t=EAte-f=EAte" to help you ge=
t your head
> together (groan!). If you can stand the occasional pun, I could help yo=
u
> step by step through the process and posting the dialog on the list wo=
uld
> be interesting for others to follow. Attached is simplest schematic for=
the
> Power_Smart head circuit re-organized a bit to make it more understanda=
ble.
> That design may be a good starting point, assuming you have access to a
> 74AC04. If not, then a 74HC04 from Radioshack will work too but would
> require an h-bridge such as the fetbridge described earlier. Otherwise =
the
> 240 version can be used but first we should agree on pin numbers, layou=
t
> component values, etc. The LEDs on the buffer outputs help a lot with
> debugging and tuning. If you are interested you (or I) can make up a la=
yout
> drawing so that we can build this unit together, step by step and debug=
as
> we go along. Sort of like a virtual BEAM workshop with anyone intereste=
d,
> joining in and providing their feedback and progress reports. Let me kn=
ow
> what you think.
>
> I was also thinking of some kind of head contest:
>
> Competitive - where the heads go "head to head" wielding laser pointers
> (well LED spotlights anyway) to blind or poke the other guys eyes out a=
nd
> generally and try to screw up the other heads. (grin)
>
> Cooperative - using laser pointers (or LED spots), draw beautiful patte=
rns
> on the ceiling while doing a little beam tech "pas de deux".
>
> regards
>
> Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
>
>
> > <>
>
>
> > -----Original Message-----
> > From: Bumper314@aol.com [SMTP:Bumper314@aol.com]
> > Sent: Wednesday, September 08, 1999 10:40 PM
> > To: beam@sgiblab.sgi.com
> > Subject: Re: PS HEAD V2
> >
> > In a message dated 9/8/99 9:24:07 PM Pacific Daylight Time,
> > beamtastic@yahoo.com writes:
> >
> > > Wilf, is there a big difference in the performance between v1 and v=
2 of
> > > the PSH? I was just curious, since I built the v1 PSH and it perfo=
rms
> > > very well for me..
> > > I'm sure this will be of interest to others, so I'm posting it to =
the
> > > list..
> > > thanks..
> >
> >
> > Well me and my bad luck were unable to breadboard this little
> > circuit...very
> > very simple circuit...sigh..so im curious if it could be because i us=
ed
> > .1=B5f
> > caps instead of .01?
> >
> > steve
>
> ---------------------------------------------------------------------=
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> Name: PSHEAD4.gif
> PSHEAD4.gif Type: GIF Image (image/gif)
> Encoding: base64

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