This is the sort of topic where it wouldn’t be a great idea to be dismissive of textbooks and/or formal instruction. Often local power line crews will put on a safety demonstration at hamfests. No doubt they would do the same for the various builder/hacker/maker spaces
I am going to try a rheostat on the input voltage to see if I can drop the rectifier output voltage to around 30v. Right now it works but will pop a15A wall circuit breaker after 15-20 seconds. But it is a super strong magnet. Limiting the current is the key I believe. More later
I’m wondering why nobody is simply rectifying a 120vac input for dc wiring the secondary coil? It means you don’t have to swap the coil location or use a dc power supply. I have a trans with a secondary resistance of 82ohms. Putting 120vdc through it would be about 175watts (assuming I do a good job of determining wire size and 1.46amps is ok)
3-phase installations like industrial facilities and some apartments are fed with 208V 3-phase, which provide three phases of 120V to neutral, or 208V phase-to-phase.
This is an important enough point that I felt it deserved its own heading: High speed shooting isn’t just about sports photography; it’s about capturing the perfect moment, regardless of how fast the subject is moving. This is a point I’ve been making since I first tested a prototype of the Casio FH20 a couple of years ago: The difference between the perfect moment of blowing out the birthday candles and one that’s a near miss can be a small fraction of a second. When shooting candids of people chatting and interacting, facial expressions and mouth positions change in literally the blink of an eye. A camera that shoots at 7 frames per second vs. one that only manages 3 frames per second can mean the difference between dozens of "keepers" and just a few.
I don’t know about anywhere else, but in North America, power enters the home via two 120V hot and one neutral. The two 120V hot legs are out of phase with each other, and when combined, you get 240V. So, from the breaker panel, you can pull 120V or 240V, depending on the type of breaker you insert at a given position. Some large appliances (water heaters, central AC units, electric stoves, large power tools) are 240V in North America, but most everything else is designed for a single leg 120V feed. Then just to make things even more complicated, large industrial businesses often have three phase 480V for the really big equipment.
Washing machines etc. have their own 10-16A fuses. 3 phase 16A power is used for larger equipment, most commonly for semi-permanent installation like oven&stove combo and electric sauna stove. Those are usually connected to star, so single element in equipment will still see 230V.
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.
Knocking over a candle would be an accident. Keeping barrels of petrol in your living room would be negligence. Doing your own mains wiring without the proper qualifications, I dunno which side that falls on. Real accidents can’t be foreseen, but you have to take reasonable precautions.
I will not put all the money on the bet, but this one might be indeed one of the solutions: http://www.mouser.com/ds/2/328/lnk302_304-306-179954.pdf if you want something “all-in-one”. I prefer a separate external PSU for many reasons, including circuit separation and protection. You can find 5V and 3.3V SMPS DIN rail mouting ones for decent prices.
Anything below 50 Volts is considered “safe”. As in, you don’t need to be a licensed electrician to build and operate it. That’s the other thing with dealing with mains voltages in a DIY project. If you build it yourself, your insurance company won’t covery you.
“Normal” mains voltage heating elements use nichrome (nickel chromium) some time called “resistance wire” because it has a higher resistance for a given surface area.
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