From: Chuck Simmons
Organization: You jest.
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Subject: Re: Piezo Ignitor to power an LED -- any ideas?
References: <email@example.com> <firstname.lastname@example.org> <email@example.com>
Date: Fri, 22 Nov 2002 01:03:14 GMT
NNTP-Posting-Date: Thu, 21 Nov 2002 17:03:14 PST
John Fields wrote:
> On Thu, 21 Nov 2002 07:18:51 -0800, J81 wrote:
> >Unfortunately I can't say why, but I need to use the piezo ignition,
> >or the general impact-causes-electricity effect of piezo elements.
> >I've seen those flashlights though, and they're quite cool. :)
> >The way the idea idea worked in my head was to get to the point where
> >I could use multiple clicks of the piezo--or multiple piezo ignitions
> >in parallel--to charge a capacitor. The capacitor would then slowly
> >discharge over time into the LED. The next step after that would be
> >running power through a pulsed power supply such that the LED blinks
> >rapidly enough that it's perceived to be constantly on, but uses
> >significantly less power than it would if it were.
> Just to find out what's what, I went out and bought a Scripto
> barbecue lighter, took it apart and hooked up the piezo cell like
> IG>---+---[CR1>]--+--[ | | |
> | [C1] |
> | | |
> The diodes are some 20kV units I had in stock, and for different
> caps, I got this:
> C1,=B5F Vpk
> 0.04 170
> 0.1 80
> 0.2 40
> 0.4 20
> 0.8 10
> 1.0 8
> Where C1,=B5F is the capacitance of C1 and Vpk is the voltage to which
> it charged after one hit from the piezo. Multiple hits drove the
> voltage higher. I didn't record the decay rates, but the load was a
> 10Meg scope probe and the decay was very much slower for 1=B5F than it
> was for 40nF, as one would expect.
> After that, I hooked up a 2mA LED and a 1K resistor across the cap,
> like this:
> IG>---+---[CR1>]--+------[ | | |
> | +--[R1K]--+ |
> | | | |
> | [C1] | |
> | | | |
> | +-[ | | |
> And, with C1 =3D 1=B5F I got a 6V, 2ms pulse across it (C1) which gave =
> clearly visible optical output pulse from the LED.
I don't see any need for high voltage diodes. (I actually don't see the
need for the bridge at all because the main pules is DC anyway.) The
capacitor will insure low reverse voltage on the diodes. You are a
little sensitive to current in that the charging current may be high.
... The times have been, =
That, when the brains were out, =
the man would die. ... Macbeth =
Chuck Simmons firstname.lastname@example.org