Samsung’s 2018 TVs now support FreeSync for smoother gaming | 25 Amp Circuit Breaker

Also, if you leave your oscilloscope floating at mains voltage with an isolation transformer puts you in danger as all earthed parts of the oscilloscope will be floating at that voltage. Again: when things are floating, it is ok to have 1 fault.. but the second fault will definitely kill you or break something as no RCD will protect you.

We did go for an L2 charger in our case because we have 2 BEVs and charging them on 1 20 amp L1 circuit wouldn’t cut it. Generally my wife uses the L2 charger for her Leaf while I L1 charge the model 3 and only borrow her L2 connection if I have been too lazy to plug into L1 for a few days. But, if we just had the model 3 L1 alone would be fine. As for the “plugging an L1 charger into a corroded outlet safety risk” some other repliers mention. Well duh. If I plug an L2 charger into a corroded 14-30 or 14:50 outlet there is even more risk. If the 120V outlet is in poor shape $5 in parts at Home Depot can fix that. Any sustained draw electrical equipment can be a hazard if plugged into insufficient infrastructure.

http://www.aliexpress.com/store/product/110v-220v-Silicone-Rubber-Heater-Bed-600MM-x-600MM-24-X24-For-3D-Printer-With-100k/709519_1847472742.html

You probably think OSHA is staffed entirely by millennials who have no idea what it’s like to lose a limb and act like it’s a big deal or something.

Think for a minute, what are you going to find inside that box? You need to consider what voltages it takes as a power supply, what it does with those voltages, where any hazardous voltages might lie inside it, and whether or not they are likely to be accessible once the cover is off. It’s important to realise that simply because an item isn’t mains-powered does not mean you no longer have to consider this, for example if you’ve ever opened a camera with a built-in flash you may have encountered a capacitor with several hundred volts remaining on it. Where is the high voltage going to be?

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I also seen a technique where a relay is placed in parallel with the zero crossing triac so the triac is only passing the load for 200ms or so while the relay switches. Since the triac is on longer than the relay, the contacts don’t arc over when switching, and the traic doesn’t pass the current all the time.

I bought an optically isolated unit that is a “Solid State Relay.” ( SSR)The insides are some kind of zero crossing SCR/TRIAC I’m sure but the key is that the input is a logic signal at a few ma anywhere between 4-30 VDC. This unit is rated to 250VAC at 50 amps. I use it with a foot switch and DC wall wart to turn my welder on and off. It DOES require a beefy heat sink for that kind of power but it hasn’t even broken a sweat (my welder uses around 40 amps give or take.) I would strongly recommend adapting this circuit to take advantage of one of the many available SSR’s out there and let a professionally made and UL certified device handle the mains side. You just drive one of these with the GPIO side here. Of course you can use a much smaller unit for doing the typical 15 Amp light circuits. I actually used such a unit controlled by an Arduino to switch a hot plate (1000 watts) on and off for my flow soldering rig where the Arduino automates the solder temperature profile. I think it is best to marry our “hacks” to these commercial components that have proven performance/certification for our mains. My two cents ‘

#PreferLinux mentioned switching off at the mains socket. Do that, but still test; that saved me once when the switch was faulty. Yes, that socket was replaced, pronto!

“If you can power the logic side with some +5V derived from mains, there is no point keeping the optocouplers, right?”

I’ve thought about converting my Solidoodle 2 to 120v bed heating for ages now. I think it’s a good idea with a lot of benefits. I’ve been far to lazy to actually do it, however. Maybe one day I’ll get my act together. In the mean time I’ll just sit here and envy other people who have had the initiative to actually do it.

But there is other sources for the “warmth”, all though, if one lives on permafrost, then many of those sources are off limits. Since it is typically either boring a hole into the ground (Not always an option due to geological reasons), putting a hose that is coiled under the surface of the ground, typically a meter or so down. (the ground temperature a meter under ground is typically rather close to the average year round temperature (though dependent on what soil one lives on). We would find permafrost if the average temperature is below freezing.) Or sinking a coiled hose to the bottom of a lake or river. Since the temperature at the bottom of lakes is typically around 4 degrees C. (This though requires that one has a lake on one’s property that doesn’t completely freeze to the bottom… (So a depths of at least a few meters is typically required for cold climate.))