Summagraphics tablet?

From: der Mouse <mouse_at_Rodents.Montreal.QC.CA>
Date: Thu May 6 00:32:18 2004

> Basically, the microcontroller triggers a thyristor (SCR) on the
> tablet driver PCB (actually iside the tablet, at one corner) which
> discharges a capacitor through a 1-turn coil around one side of the
> tablet. This causes a magnetic pulse to propagage down metal wires
> across the tablet. IIRC, it sets up magnetostrictive strains in the
> wires, and thus propagates essentially at the speed of sound.

I'm not sure how accurate this is for the pad I have.

The pad is a two-layer PCB, with the working area covered by a grid of
printed-circuit "wires", in one direction on one side of the PCB and
the other direction on the other side. They are surprisingly far
apart, on the order of ?". I haven't traced the circuitry enough to
know how accurate your description is, though I didn't see anything
like the one-turn coil you describe - everything electrical, besides
the serial connector, power, and the puck, is on the PCB. Two parallel
etch runs could form a one-turn coil; I don't recall seeing them, but I
also wasn't looking for them.

Perhaps when I open it up to investigate the DIP switch banks I'll be
able to tell.

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Received on Thu May 06 2004 - 00:32:18 BST