High power pneumatic switch

This is a high power switch which can be used to switch almost anything. It is designed to enable / shorting large capacitor banks for maximum energy transfer. Applications: Can Crusher, Disc Launcher, Rail Gun, etc.

I chose to smash a copper piece into an aluminum block, I thought it might reduce the contact welding and sticking because of the two different metals. The copper rod is 25x25mm with two M12 threaded holes. At 8 bar the cylinder delivers a force of about 500N (50kg). The cylinder is driven by an electrically activated valve, this valve controls the switch and is open at rest (NO contact). Welded contacts will be pulled loose with 50kg by the air cylinder.

To separate the copper electrically from the frame, I put it on a 4mm aluminum sheet. This sheet was bolted to the cylinder with 4 M6 nylon bolts, with an 8mm acrylic sheet between.

To test it, I connected my old (small) capacitor bank directly to the switch. The bank contains about 1 kJ at 400V. The discharge current is at least 3kA. I was surprised how few sparks actually came from the switch contacts. The capacitors don't like this kind of abuse, but they'll survive.

A short demonstration video, the sound is truly deafening.

Some pictures of construction, etc.:

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