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