Monday, April 18, 2005

Vik has tried an experiment with his circuit idea. He says:

"I did a quick experiment with conductive silver paint. I Stretched out commercial PVC food wrap over a box lid and daubed tracks 1.5-2mm wide on it. When the paint had cured, EVA hot-melt glue was applied to cover the tracks in an approx. 0.5mm layer.

"Spare component leads were pushed through the PVC into the EVA via the paint. A resistance of 0.6 ohms was measured across two test leads inserted into circular pads at each end of a 25mm line.

"The pen tip is not a fibre tip, but reminiscent of the old correction ink pens, and the particular one I had was prone to clogging. A syringe-based system may be more appropriate.

"I'll leave the samples for a week and see what happens to them. If all is well, I'll attempt to assemble a simple electronics kit. This should be achievable by stretching the PVC over the copper side of the board,
tracing out the tracks, and pushing the components through. I might mount that one on drilled plywood though."


Here is the latest Wood's metal deposition head design from Ed Sells, all made by RP:

(To see the original look at the blog for March 23 2005.) This one has a hot-air heating jacket controlled by a thermocouple thermostat, and drive feedback from the optoswitch you can see at the top of the picture. The whole thing is straightforward to control with a PIC and the rather neat H-bridge BA6286 from Rohm. When I can get myself (and more importantly the data) organised I'll put all the designs and software up on the Documentation section of the website.


Thanks to my colleague William Megill for drawing the following measuring device to our attention; he says:

"It's basically two thin copper wire coils set in a sleeve of silicone rubber. As it's stretched, the coils get further apart, which changes the capacitance. Strains up to 150-200% are no problem."

See this link for details.

Thanks for the suggestion. Done.
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