Charting the S&P 500’s range-bound, but bullish, (unofficial) summer start | 19mm Momentary Push Button

I’ve been bit in a big way only three times. Two of the three were “Trust but don’t verify” issues, and I learned from them – always verify, no matter what anyone says.

Yeah, dont use these. Use a relay instead. There is a reason all the high end stuff went away from the Triacs as they will float to full mains voltage when no load is connected and you get electrocuted when you mess with the circuit. AMX, Crestron, Lutron, etc all have moved away from pure Triac control due to this safety issue.

MLVs come in various chip form sizes, and are capable of dissipating significant surge energy for their size. Thus, they suit both data-line and power-supply transient-suppression applications.

Why not use a silicone pad block heater for cars? You glue them on, they run on 120v and work good. It’s robust enough to sit on the bottom of your engine, in elements and gravel spray from the road, for years. They even come with a little tube of aluminum adhesive. Seems like a pretty good fit.

But at the end of the training it says “you can ignore all of this if you are troubleshooting”. If you are afraid of live circuits, stay at your desk where it is safe…

continuing akismetuser212339447″ Using a mechanical relay for your thermal control _may_ make you crazy with the clicking. If you think you can take the madness, keep an eye on the make/break current rating, and the lifetime switching at the design current. Switching current and voltage is often far less than carrying current, and electrical contact life is short compared to mechanical life (Switching at zero crossing will help). Also note that failure mode of relays is possibly contacts fused closed – design with safety in mind, and have some sort of feedback. Something like a thermal cutoff fuse?

Chassis floats with just 2. My folks lived in the middle east before my dad retired and I visited them in 2013. You could feel 50hz on the refrigerator door handle. Touching their aluminum iMac gave a nastier jolt. I remember my dad telling me, “yeah, don’t touch that” after trying to plug in a USB stick.

If a consequence is human death then obviously that is completely unacceptable. If it blows a fuse at 1000V then good! If traces vaporise disconnecting the mains at 10,000Votls then well done! Where is the weakest point (lowest creepage clearance for the exposed voltages) and what are the consequences of a flash over at that point.

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After checking to make sure the outlets are wired correctly, a 220v light bulb with light up across the two hots if they are opposite phase and not if they are the same phase.

Of course in many parts of the world that’s not possible like it is here in the US where better than 60% of homes have access to NG

– Use isolated differential probes to measure high voltage. – Use current clamps or current transformers to measure current. – Put bleeding resistors in any big capacitor in your circuit. – Don’t change the position of the probes in the power circuit without power everything down. – Don’t work with high voltages alone. – If there’s more people involved in your experiment, block any circuit breaker, button or at least put some signs to prevent people from turning them on while you are messing with the circuit. Paranoids may even ground things while they are playing with the installation to direct the current to the ground in case someone makes a mistake.