Charting the S&P 500’s range-bound, but bullish, (unofficial) summer start | Lrd12 Overload Relay

The device uses a triac to do the switching, and is optically isolated from mains. Be sure to check out the video after the break to see the device in action. All in all, this could be a great way to get started with home automation, or maybe just do something simple like build a timer for your floor lamp. Anything is possible!

A fun read is the Boeing’s space station power system document that describes the DC power system on the ISS: http://www.boeing.com/assets/pdf/defense-space/space/spacestation/systems/docs/ISS%20Electric%20Power%20System.pdf

Over and over again, I have heard HVACR technicians and electricians quote rules of thumb regarding wiring sizing, and I have witnessed and participated in many heated debates on the topic.

Before we get too deep into this topic of wire sizing, let’s acknowledge that while detailed conductor sizing is the job of engineers and electricians (not HVACR technicians), there are many cases where contractors are tasked with assessing whether a breaker or conductor (wire) is adequate in both retrofit and service situations.

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…

The only thing I would add would be a (redundant) circuit breaker (Airpax, Heinemann, et al) on each input that was two-pole with a common trip bar. That, and I would build it in a metal enclosure.

During service calls, being able to identify undersized conductors can help resolve compressor start issues or intermittent trips of breakers or fuses. Knowing appropriate and inappropriate breaker and conductor sizes will save you and your customers time and money.

If you know the Wattage of the transformer and the input voltage of the oven then you can calculate the approximate current the primary (thicker wire) can carry. Example: 500W 220V gives 500 / 220 = 2.273 Amps. This is the current the coil is designed to carry, and this current should normally take the core close to saturation without generating too much heat. The coil resistance can be measured and an appropriate DC voltage applied. I suggest a current of around 1.5 times as long as the power is not ON permanently. Regarding the use of both coils, the secondary coil is much finer wire and will require a proportionately higher voltage. Assuming the output voltage to be 2500, then the current required will be 500 / 2500 or 0.2 A. The secondary coil has worse properties for dissipating heat, so I would only allow a 25% over current, but just try it and if it gets too hot to hold, reduce the voltage. Allow 20 minutes for the coil to cool between tests. Putting the coils in series, or in parallel does not make sense because they have such different characteristics: better to find two ovens with the same transformer and use both primary coils or both secondary coils, which can then be connected in series to raise the working voltage or in parallel to keep the voltage down but double the current. As someone has already said above, disconnecting the coil produces a spark, that in the secondary coil will be a very high voltage – use a totally enclosed switch rated at at least 250V 10 A, with a 100 Ohm resistor in series with a 0.1 microfarad capacitor across the coil to reduce the sparking and increase switch contact life.

In plain English, what that means is that the thing AIN’T CERTIFIED FOR ANYTHING. It just means the device has met MINIMAL safety concerns, when operated under typical conditions. It doesn’t say anything about out-of-the-ordinary conditions.

The few I bought on AliExpress all had 50% rated triacs in them vs. description. “Luckily” I contested them all for 50% my money back and could use them for lower power projects later

Here is something to think about; Those floor finishers were doing this back in the days when “the code” only specified two wire outlets. . These days that would make a few people nervous. No case ground for the sander….

You also need to insure that the hot line is completely isolated from the neutral line other than via the intended switching and power supply paths. Insuring that is a hell of a lot easier when you use registered isolating components to do it.