[chbot] Robotics Group meeting, 5 Idris Rd, 6-30pm, Monday 20 Dec 2021

[Mark Atherton]

Robotics Group meeting, 5 Idris Rd, 6-30pm, Monday 20 Dec 2021

Hello everyone,

Good turnout with 20 attendees, and lots of huddles-of tech-talk. $24 + 
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

Russel kindly donated some huge cracked, but working solar panels. These 
were almost immediately purchased by keen member who loaded the brown 
box on the wall with pieces-of-eight.

Graham kindly donated several huge moving LED text indicators. These 
were swallowed up in a similar manner as above.

Evening started by passing around a solenoid-driven EHT safety discharge 
assembly.

First talk was by Mark on the subject of over-voltage Drain protection 
of a broadband LDMOS push-pull RF power amplifier. Standing DC + 
rectified RF on the Drain was used to fire an SCR should Drain voltage 
exceed +66V. The SCR shorted out the 5V bias regulator(!) removing Gate 
bias from the LDMOS device, thus closing it down.

There was a brief video on the subject of destroying a Tesla E type 
using a few kilos of C4. Rather festive.

William demonstrated his latest home-made serial ‘286 plug in card (4 
layer, gold plated) based on a 16550. Also, a demonstration of the DOS 
based 286 diagnostics.

Rudy gave a demonstration of an air-cannon, with visualization provided 
by a smoke generator. Hopefully the smoke will clear soon J

Andy gave a talk about a high-pressure gas-management system associated 
with an air-conditioner. The gas valves were managed by magnetic 
coupling. Very neat solution to a tricky probelsm.

Bevin brought in a (large) rotary slide rule he found at a local surplus 
store. Amazing technology good for 5-digit resolution, and apparently 
used up until the 1960.

Michael talked about the latest work on his oil-mist powered casting 
furnace. Burning oil-mist will allow the associated crucible to reach 
much higher temperatures than is easily possible using a 230V/20A 
electric heater, and using waste oil. This is going to be quite 
something to behold when it is powered up.

Robin talked about his exploration into Embedded Trace Macrocell (ETM) 
of the Cortex 3 series (and above) STM32s. The ETM can be configured 
using and external debugger, or programmatically, and can provide a 
whole wealth of real-time CPU health and status information.