Motor Nameplate Current vs. NEC Full Load Current Values | National Electrical Code | 220v Contactor Relay

Don’t blame the Chinese for this one! They are more than happy to sell us any quality we want. For example, you are probably reading this on a very well built, Chinese made, smart phone.

As someone who started playing with electronics in the days of B+ in the 350VDC range with double that across the main xformer’s secondary, I was utterly appalled at the idea of tying myself to a hard ground when working with some of the newer (for the time) solid-state stuff that was coming out. We had a respect for high voltage then that is often missing these days, this article is an excellent reminder that this is still needed.

While we didn’t encounter any exposure accuracy issues in our lab tests, I had a little trouble with the Sony A33 and A55′s exposure system in the field. Under bright sunlight, I was generally shooting with -0.3 EV of exposure compensation dialed in. Looking at my photos on the computer later, it seemed that many of them really could have used -0.7 EV. The overexposure bias seemed fairly universal under bright lighting, regardless of whether the subject itself was low- or high-key. Shots under lower lighting didn’t seem to have the same issue, though.

We recently watched [MakeItExtreme] turn a couple of microwave oven transformers into a somewhat ill-advised wall-climbing rig. It looks like that may have been the inspiration for this build, and the finished product appears to be a tad more useful this time. The frames of three MOTs are cut open to remove the secondary coils and leave the cores exposed as poles for the future magnets. A shallow dish is fabricated out of steel and the magnets are welded in place.

I don’t know, disassemble an induction heater, use the encased induction coil, feed it with mains, put a metal plate on it, and you got a safe but cumbersome heated bed using mains.

Because a failure of the sort I have described will not be current limited. You’ll likely start a fire.

The plug-in Kia Niro has an 8.9 kWh battery (vs. 1.6 kWh in the regular car). You can quickly estimate the amount of kWh you used in the week as long as the battery was fully drained every time you plugged the car in (it’s fully drained if the gasoline engine kicks in) and you know how many times you charged the car.

The back-EMF voltage generated across the start winding causes a small current to flow in the start winding and potential relay coil, because they are in the same circuit. When the back-EMF has built up to a high enough value (referred to as pick-up voltage), the contacts between terminals 1 and 2 will be picked up (“opened”). This will take the start capacitor out of the circuit.

That said, why not use 12v halogens (or even mains voltage halogens) to provide the heat? They are ~99% efficient at that, cheap, plentiful, universally available…

SSRs can actually contain what is used here: optocoupler+triac or they may use optocoupler+mosfet. Just like individual triacs you will find that they suffer from the same issue: high power dissipation. A quick looks shows BT137 will burn 20W to switch a 5A load, I see 6W for the first 10A SSR I encounter. This is too much to dissipate in a small junction box isolated inside a wall. Meanwhile, a 10A relay will dissipate maximum 2.5W through the 0.1ohm contacts.

When we moved from the UK about 15 years ago, we lived in a PME TN-S property and my ex neighbors house is still connected thus. Newbuild and current standard might be to try to retrospectively phase that out, but its still a generalization to say all properties will be TN-C connected. If your in a TN-S property, its my understanding that ignoring that layout and putting your own earthing system in and bonding it to the supply one, can result in ground current back flowing through your system from neighboring properties.

Two inputs for the beefy converter are supplied from outlets not just on separate circuits, but on two circuits whose hot lines are 180 degrees out of phase. That means identifying where there are two plugs, not protected by GFCI outlets or breakers, which are on two separate hot lines of split phase power. To protect the user, [Nick] designed in a set of relays which kill the circuit when one of the two supplies is unplugged. A system that didn’t have these protections would have mains voltage on the prongs of the disconnected plug.