[chbot] Robotics Group meeting, 5 Idris Rd, 6-30pm, Robotics 15 Aug 2022

Mark Atherton markaren1 at xtra.co.nz
Mon Aug 15 10:50:29 BST 2022

Hello everyone,

Good turnout with 16 attendees, and lots of huddles-of tech-talk. $17 + 
change (in gold, and flat-money) collected and transferred into the 
robotics loose-change jar (for later banking).

All sales from the trading table should go into the brown box on the 
wall, and are directly for the benefit of our host club, Christchurch 
Amateur Radio Club, NZART Branch 05.

Equipment donations are welcome for the trading table, but no CRT based 
product, printers, toner or items that are likely to be a disposal burden.

With thanks on behalf of the group,

Mark Atherton


Ian MacPherson came into to mute the noisy radio in the radio room; 
thank you. We would have had a difficult time with an unsquelched radio 
rattling away loundly in the background !!

Mark talked about a pin-optimization technique used by Andrew Woodfield. 
Andrew needed to attach a rotary encoder to an ATtiny85, but all of the 
pins had been used (except /reset). This last pin can also be used as an 
ADC. Since reset is only active below 2.5V, the region 2.5 to 5.0V can 
be used to read a rotary encoder with weighting resistors attached to 
its two outputs, and a suitable pull-up. Very cunning.

Mark continued with a discussion about the development of a Thyristor 
driven EHT pulse generator using a DIAC trigger device, and a 12V pulse 
transformer. First attempt used an ignition-coil from an All Terrain 
Vehicle, and 28 milli Joules of energy. The coil was utterly destroyed. 
Next attempt will be using a more traditional (old school) ignition-coil.

Mark also passed around a 1 inch dia CRT along with a mystery ballast 
device containing two incandescent lamps and some precision resistors.

Graham talked about the reuse of an old electric iron cable (for high 
temperature applications), and a significant insulation failure found 
with one sample.

Michael brought in a home-made laser-cut lighting gobo. He also talked 
about his experience installing a home-solar system.

Darren brought in some EV car dash clusters to demonstrate the art of 
reverse engineering the comms protocol.

William brought in a home-made large LED clock with temperature.

Robin talked about his trials and tribulations re-provisioning a VOIP ATA.

Volker talked about some (very) low cost calipers, as well as an 
air-quality meter he purchased.

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