# Project Codename Puffer

A project to build an airgun whose piston is actuated with a solenoid ala gauss gun style.

# Notes

NiMH batteries appears to be the way to go due to their high-drain capabilities.

Rechargeable D-Cell batteries with 10Ah available here

Diameter of 33.2 ± 1 millimeters (1.3 inches). Overall length of 61.5 mm.

With 4 D-Cell batteries, some possible power configurations:

10Ah @ 4.8V 20Ah @ 2.4V 40Ah @ 1.2V

Two of the transformers currently available from scavenging are 10:1. I could use a booster converter as well, or chain multiple transformers together, or attempt to changing the windings.

I may be able to scavenge an old 20:1 transformer (a mains powerbrick for going from 120V → 5V). I might be also able to scavenge or otherwise source a UK/European 5V PSU–that would be designed to take 240 → 5V meaning a 40:1 winding.

Regardless, my target is 330V. It would seem that I cannot go straight from my battery source, not without increasing my cell count (at the cost of Ah, no less).

The firing capacitor(s) have been scavenged from old external flashes.

## Problems and Constraints

• Constraint I'd like to run off a single D-Cell battery. Per my math, even if I go for a 2400 MFD capacitor bank (at 330V), a single D-Cell has enough Watt-Hours to charge over 300 times. The ease of changing out and cool-factor of replicating the single-cell power source of energy weapons from Fallout is very appealing.
• Challenge How do I get a more workable voltage out of a 1.2V cell? I need about 3 volts to drive the ARM microcontroller. If I want to use one 10:1 transformer, I need at least 40 volts. The MCU isn't entirely necessary–a 555 to generate the AC signal and an op-amp, voltage divider, and transistor can be used to stop charging and indicate when the gun is ready to fire. I could use a ready-made booster-converter circuit board, but those have limited amperage output. I could drive directly from the battery, but to reach the target 461V, that's a 384:1 winding ratio. I'd either have to make a transformer or buy one. Neither are really doable. I could link two of my 10:1 transformers together for a step up of 100:1
• Pragmatic Solution Just use more batteries for greater voltage. Bleh. Shitty.
• Ideal Solution Have a 300W, 384:1 transformer being fed directly from the bank of high-Amp MOSFETs.