What Most Techs Get Wrong About Wire Sizing | 2017-09-18 | 19mm Momentary Push Button

Eh, boneheads frying themselves or setting their houses on fire because of DIY approach to mains wiring are hardly something new that can be blamed on the “maker movement”.

I can see the benefit of inspection, I guess (that none of your wires popped off or something?). My comment on the relays was not that they were unsuitable, but that using the 240v coil as a 240v detector may or may not be entirely reliable because of holding vs. draw-in currents, box getting dropped, etc. although that’s edge-case engineering to an excessive degree and it really is perfectly fine.

not exactly mains but when i was a kid i enjoyed playing with photoflash caps and at one point had one fully charged to about 330V and discovered the negative post to the AA battery was also connected to the cap and put the entire shot up one arm, across my damn heart and out the other arm, my whole body locked up for only about a second (maybe 2) and i think i fell over (like people in taser videos but i was sitting). it sure shook me up and im glad it was only a small cap

15A is more like 1,500 times what’s required to kill you, depending on what part of your anatomy it finds to traverse.

Found said bare wires and had the ultimate Homer Simpson moment after separating them (probably when the lights weren’t plugged in), and thought ‘hey wouldn’t it be fun to complete this mains circuit across my body’. I didn’t really check with the lights lit up, but I was having a whale of a time juddering and screaming for a few seconds till somehow I managed to let go of the wires

When the cycling control opens, line voltage is taken away from the motor. The motor’s rotor decreases in speed. Thus, the back-EMF generated across the start winding decreases in magnitude. The relay’s coil now sees a lower back-EMF and no longer can generate enough magnetism in its iron core to keep contacts 1 and 2 open.

The leads on that TO220 case SCR and that solder trace are not going to handle 20 amps continuously without heating up. A SCR that’s up to the task of carrying 20 amps for hours on end would have a TO-218 case or even be stud mount. If all else fails you could just use a contactor relay which is what they normally use for this application.

A vaccum forming table design I looked at used ceramic rods made the same way with reflectors to evenly distribute the heat. I also own an electric kiln designed to heat and temper glass so a page can be taken from that design.

It calls out a MOC3041M on the silkscreening. One can use a MOC3041 of course as they are the same form factor.

Agreed, this is a house fire waiting to happen and your insurance co. won’t give you a cent if an investigation points to this homecooked thing as the firestarter. There are numerous commercial alternatives which are small enough to fit in a junction box _and_ are UL/FCC/CE approved. Granted, they aren’t as cheap as the ESP module and the triac described here, but in the end, most cheap alternatives to switching powerful currents turn out to be very expensive after all.

Is it possible, that the discreet triplers (vs. diode split transformer) were in the time of BW-TV? They had lower power. Or the guy tested the AC before the tripler, I think that would make a great difference. Although I also would not do this intentionally. There would also be a nice arc to a grounded screw driver, if you want to test the HT – without any current path through myself, what I really prefer. The electrician, whom you mention, did he really die while testing for voltage with his hand, or was his accident unrelated to this?

This makes no sense when you’re designing a heater. The higher the current, the hotter the wire will be. That’s why power companies transmit power at high voltage in the first place: they want to minimize heating. 120 watts flowing through a wire does NOT mean that 120 watts of heat are dissipated in it. You’ll get a much more efficient heater at lower voltages and higher currents.