Select the Right Varistors for Overvoltage Circuit Protection | 220v Contactor Relay

Earthing is thus a vital part of power distribution safety. The only snag with open equipment on your bench is that any earth connection becomes a valid part of the return circuit for the power, and since that earth connection can come through you, that’s dangerous. The isolating transformer breaks that earth circuit for your bench, thus removing that particular hazard. The upshot of this is that you can safely touch either one of the two wires and because there’s no path to ground, you won’t get zapped. (Touching two wires completes the circuit. You still have to be careful!) Isolation transformers are also used to lift the ground so that you can connect mains circuitry up to your oscilloscope, even though the black probe clip is connected to earth ground.

A word of advice: if your idea of working safely on mains-powered stuff hinges on an RCD protecting you it might be a better idea to put down your tools and back away, slowly…

If you run a separate earth wire that is hard grounded at the sub and hard grounded at your house and nowhere in between. In this situation if you get a lightning strike at or near your house then the ground potential rises. This flows through the earth wire to the sub ground and can be a massive current, enough to make the network fail dramatically. This rise in ground potential can also be caused by other things such as a faulty insulator on an MV or HV tower (pylon) or pole. Even if insulators are good then you can still get this ground potential rise. You can easily measure it with a length of wire and two earth spikes, put one near a tower and the other a distance away and you can see a significant voltage. If you also have a separate wire called neutral running form the sub then the potential between that wire and the earth wire is unknown so you have a risk of lethal voltage between neutral and earth, a situation that is not expected and potentially extremely dangerous.

A properly wired, properly functioning dimmer switch can get hot to the touch. I’ve found that a 65-degree temperature rise is normal for a maxed-out dimmer. If the ambient temperature is 71 degrees and a dimmer switch is at 136 degrees, I’d be concerned, but I wouldn’t report the temperature as a problem. I would, however, take an extra minute or two to figure out how many watts the dimmer is rated for. I’d then make sure there wasn’t too much being controlled by the dimmer.

The nostalgia for “classic” miniature consoles isn’t ending anytime soon, either: Sony just announced today it’s making its own PlayStation Classic console. The tiny PS1 will come with “20 genre-defining titles,” and it’s set to release this December for $99.99. Also coming this winter is the Sega Mega Drive collection on the Nintendo Switch, and the trailer for it was published today.

You won’t always have to group them together through the app, either. If a Sonos device is playing AirPlay 2 audio, you can just push and hold the play button on an older Sonos speaker to have it automatically pick up that same source.

And this AC vs DC case when it comes to skin effect, is a reason for why some Data centers use DC distribution, as most server products uses switch mode power supplies and therefor has an internal bridge rectifier.

Waterjet, who seemingly has no concept of how a basic opto-isolated diac-driven triac circuit works, chimes in with useless blabber about insufficient current ratings of the *optoisolator* — seriously? If you’re going to throw stones at someone, perhaps you could verify that you have somewhat of a clue of what you’re talking about?

I’m a bit disappointed, I thought this was a safe place for dangerous ideas. If you want to diy an ELV heat bed go ahead, but that isn’t going to suit everyone.

The more you think about this the more you realise that there is actually no truly bomb proof way to organise it but the methods now being implemented are probably about the safest way for most situations.

But Mike I would gladly clean under your stove for around 3kW of free power… Ahh ok so his parent’s don’t have a 220/240 outlet, makes much more sense now. In that case its a purpose driven hack, elegant in its simplicity.

I’d love to see a follow piece on how to work with High Voltage as well. Lots of interesting projects to do with microwave and neon transformers…