Fusion Message Board

In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.

Subject: Re: Novice Questions
Date: Jan 29, 7:16 pm
Poster: Tom Ligon

On Jan 29, 7:16 pm, Tom Ligon wrote:

>7. We were planning on buying a small spot welder for grid construction until we found there is no such animal. The posting on building a spot welder was very helpful. I've got several fair sized capacitors rated at 3000 ufd @ 50 VDC. It seems too simple to just get a 50 volt DC power supply and hook it up to the capacitor and the spot welding electrodes. It seems we could easily get a nasty burn from this setup if we're anything other than totally alert. What else are we not understanding here being novices?
The spotwelder I use is a very old reconditioned commercial model, rated at up to 80 watt-seconds (joules). It uses electrolytic caps charged to up to about 400 volts, then discharges them thru a step-down transformer to get high current at low voltage. 50 volts is safer than 400, but still possibly lethal (you can get a tickle at 24 volts and can conceivably kill yourself as low as 35 volts). Try running the caps directly at 24 volts or so if you can find a small supply to charge them, or step the voltage down with a transformer (good junkyard item).
Regarding the hydrogen issue, you might "cheat" by getting someone to give you an occasional wiff of hydrogen you could store in your cylinder. Backfilling an existing tank to 7 psig is not technically legal, but it is safe. If it leaks it is no more dangerous than a bad case of gas, and you would not need a regulator.