The Walking Dead developer Telltale hit with devastating layoffs as part of a ‘majority studio closure’ | 220v Contactor Relay

Don’t those wild & crazy Brits use “electrocution” to include a non-lethal shock? Our friend [Moryc] could have learned English from Britlish speaker, as he mentions that he’s not a native speaker of our bastard tongue (though, he could have fooled me with that delightful prose).

And even today people give the advice of plugging a computer in the wall and grabbing the metal case as you’re working inside it. Bad idea – if the PSU has failed, you may very well have live voltages in the boards.

You could make a multimeter that had an internal switch for volts / amps. But I think electricians wouldn’t trust it. So it’d be a useless feature, as well as, probably, increasing the shunt’s resistance. And be another point of failure somewhere dangerous. Etc! Nobody wants a multimeter that killed their mate.

In college, I was playing with our nitrogen laser which had a huge exposed Blumlein discharge capacitor. So large that a bottle with fluorescent die had been set on it. While the laser was running, I picked up the bottle, and received several 20-30kV discharges to my hand. The exit was my bare feed on concrete. I was able to count the hits afterward, because each one left a small burn mark on my hand. That hurt.

There are split-phase premises supplies and three-phase. Split-phase is used for residences and small businesses, and three phase is used for larger businesses and some larger multi-tenant buildings. When using two of three phases, they’re 120 degrees apart and the nominal voltage is 208 volts. When using both sides of split-phase, the two are 180 degrees apart and the nominal voltage is 240 volts. The nominal voltage from one phase to neutral is 120 volts.

The run and start capacitors provide the phase shift for starting torque because their capacitances add up when wired in parallel. In fact, both capacitors are wired in series with the start winding and in parallel with the run winding.

In the above, the first was the result of a fault condition making a sub part of the internal chassis float at HT voltage. The second was the result of a “friend” jokingly giving my shoulder a shove when I was working.

Stripping wire with my teeth (my front teeth have a perfect gap at the bottom for it, I could probably specify them in AWG) to fit the socket onto a phone extension cable. While rather stupidly forgetting I’d plugged the damn thing in downstairs. Yowch! Fortunately it wasn’t ringing. As a mistake, it was educational.

Yes you are correct, I was remembering from just people recommending power USB power supplies, but looking at the latest data, it seems that current is always less than 215mA. That chip looks good.

The very first point to make clear when writing an article like this one is that you should disregard any ideas of “safe” voltages or currents. While the story about some significant number of people who die every year from licking a 9-volt battery is probably an urban legend and you have little to worry about from low voltage equipment, it is best to look at any higher voltages as potentially dangerous and react accordingly.

On our case a combo was the right solution. We use a contactor (a relay) to switch incoming power because it’s either on or off. But we use a SSR to switch elements on and off because they cycle on/off many times a minute.

In the next part of this article we will venture inside some of the typical devices you will be working with to examine the individual hazards and techniques you might encounter.