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You do in fact need to be a licensed engineer/electrician to design stuff with mains voltage, or you need to have your work inspected and signed for by one. It’s not just a matter of good instruction – it’s illegal for the regular Joe to even repair mains powered circuits beyond swapping a frayed power cord.

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When it comes to celebrating the arrival of 2019, Clark County’s got everything you can think of, plus a little…

In salt water – which approximates human flesh, the skin depth at 1 MHz is actually 25 cm which means your arm is a pretty good conductor through and through. The illusion of safety comes from the fact that the frequency is too high for the nerves to react, so you don’t get spasms or cramps and you don’t feel the heating that’s happening below the skin because there’s no heat-sensing nerves there and those at the current entry points have died already.

Please nobody get one of these boards. It is not a safe design for working with mains voltages. This guy has not followed guidelines for minimum creepage and clearances between the low voltage and mains side. You think it’s optoisolated and it may work fine for the majority of the time, but as soon as a mains voltage spike comes along it could bridge the gap and zap your circuit and you if you’re touching it (and your computer if you’re doing doing dev work at the time).

This. An isolation transformer can be a very useful thing, but also very dangerous. If you touch ONE end no problem, but if you touch both ends you will get cooked and the RCD will NOT trip. Or more directly: An isolation transformer does NOT allow you to switch off your brain! And NEVER connect a scope to such a transformer.

It’s not all a bed of roses with video and live AF on the Sony A33, though. While it tracks action very well, focus actuation with the kit lens is far from silent: In anything but a very loud environment, the "chock… chock" of the lens’ focus operation is painfully apparent in the audio track. Even with the ultrasonic motor-equipped Sony 70-200mm f/2.8G lens attached, focus noise was quite audible in quiet environments. Another really annoying (and entirely avoidable) audio artifact is the loud click that’s recorded at the very end of each video clip; the sound of your pressing the video on/off button to stop the recording. I experienced this with the NEX-5 as well, and it honestly seems like a bug to me.

Probably best to derate to 1.5x or 2x. But even then, are the “solder” conductors inside really going to be any different? Looking at then they appear to crate a conductor way bigger than 25A requires.

It’s just sensible to avoid risks where you can. If it doesn’t cost much extra, why not bother? Tinkering with a 3D printer is likely to take concentration away from other areas. Low voltage is intrinsically safe from electrocution. Don’t make things dangerous for yourself.

There are notable advances in interior quality and function, most significantly with the dash getting a complete overhaul that includes better materials, layout and an eight-inch screen operated by buttons and touch as standard. It’s both smart and reasonably intuitive, albeit slightly short of some of the slickness of VW’s various systems. As is common in the class, Toyota has expertly put the best materials where you are most likely to see and touch them, with hard, basic plastics mostly hidden in corners of the car.

A mains isolation transformer. wdwd [GFDL], via Wikimedia CommonsAn isolation transformer isolates the mains supply from the earthing system. This does not change any of the risks inherent to the mains voltage or other high voltages in your device, but it does provide you with some level of protection should you accidentally provide a path to earth from a live component.

Why reinvent what is already on the market? There are heating panels beeing sold as accessory for 3d printers already. I just saw a 300x200mm 200W 230VAC silicone heating pad for around 90$. The vendor (multec.de) however clearly states that the installation has to be done by a certified electrician. I’m pretty shure these pads could be sourced a lot cheaper on other sources too. If you think you can just DIY around with 230VAC, make a mistake and hurt/kill somebody or burn down a house, you will be f”cked for life, because no insurance company will cover you. And if you kill yourself and have a family, well, thats not that great for them either. Keep that in mind. I’d rather use a bed made for 48VDC. Powersupplys are abundant for that voltage (standard for a lot of telecom/industrial equipment), reasonably safe to work with compared to 230VAC, and you still get 4 times lower currents (or more power at same current) compared to a 12V bed.