Halo Style 2 stage COILGUN

[AnselmoFanZero]

The first coil of my 3stage pistol has 60J..the next 2 150J...dont wanna waste too much energy on the first stage, because the projectile isnt moving yet, its the most inefficient stage. Plus: It will be semi-auto and the ammo-clip holds the slug...a resistance I have to work against...so the first stage-eff will be even worst.

 

[Prototype]

I still haven't worked out if this is going to be a semi-auto or a single shot reload. I'm most likely going to go with semi-auto, but I have *no* idea how to design it. I've got an idea in mind, but I'm not sure how I'd implement it, it would place the slug in the coil for best efficiency, as well as being really simple, but I'm not sure yet...I'll get it drawn up for you guys tomo...today so you can see what I mean.

 

[AnselmoFanZero]

The video introducing the 3 stage 350J pistol will be a how-to-video, so you can check my design and go from there. Will test the mechanism today or tomorrow.

 

[millirad]

Ok, so I have been blowing up a few camera charger circuit cards(smoke coming off very lightly) and an occasional cap has also failed here and there(with no visible sign). So what I'm finding is that using disposable cameras, it's best not to go for more than about 2000uF, per stage. I have dropped from 6 layer 21awg to 5 layer for the purpose of speeding up the pulse. This has been successful in achieving a more powerful projectile, however this shorter spike of EMP is harder on the charging circuit boards and in some cases a cap fails.

I have burned out so many disposable camera boards, that I'm on the hunt for some more at my local photo shop which usually isn't a problem.

If I use a 6 layer coil vs a 5 layer coil, the weaker/longer pulse isn't as hard on the components, but the projectile power is reduced slightly. I think I can live with a 6 layer coil and 2250uF stage from now on. This is to extract the maximum reliable "free" power available from disposable cameras.

 

[Leodahsan]

EMP? Do you mean, the destructive wave that destroys electronics and components? Try this.

now talking serious:
if Prototype wants a semi-auto design, he'll surely needs an auto-reloader or something that forces the projectiles into the coil barrel... I cannot say anything more as I haven't tried it yet, I can just say that 134J @ 350v = 67W charger (I think, for 0.5sec charge time), so more caps in parallel would multiply this value... hence a more expensive inverter/hv-generator.

 

[AnselmoFanZero]

I believe I mentioned that before....using one charger per stage and maybe add a stage ^^

How about moving the loading switch, so that there is no connection between charger and cap (-)....that should protect the charger.

 

[StridAst]

Ok, so I have been blowing up a few camera charger circuit cards(smoke coming off very lightly) and an occasional cap has also failed here and there(with no visible sign). So what I'm finding is that using disposable cameras, it's best not to go for more than about 2000uF, per stage. I have dropped from 6 layer 21awg to 5 layer for the purpose of speeding up the pulse. This has been successful in achieving a more powerful projectile, however this shorter spike of EMP is harder on the charging circuit boards and in some cases a cap fails.

I have burned out so many disposable camera boards, that I'm on the hunt for some more at my local photo shop which usually isn't a problem.

Have you tried Barry's coilgun sim? if you can calculate your pulse with it, you can figure out if the pulse crosses into the negative. I think it's the negative side of things that's bad for the components. I've seen people talking about wiring diodes in anti-parallel with the coil. and adding resistors to counter this. There is a circuit diagram on this guy's page showing this. It might help. Again, I've not gotten as far on my coilgun as you have, but I'm trying a lot of reading

I think a downside is it lengthens your pulse. but that's the gist I have gotten from several other people's posts on other forums.

_-= Uzzors2k =-_ Project Site

 

[AnselmoFanZero]

No idea if its that bad for the electrical parts, but what you wanna get is a clean high positive peak...in general..specially for the last few stages.

 

[Leodahsan]

problems with negative peaks can be solved with ultrafast diodes antiparallel to the coil, right?

 

[AnselmoFanZero]

Protecting from back EMF...in German the Freilaufdioden
I installed some...antiparallel to the coil...no idea what would happen without them. Dont wanna know I guess ^^

 

[Leodahsan]

your caps could blowup or get damaged.

 

[AnselmoFanZero]

You shouldnt repeat what you read or heard that often ;-)
Check out what the V-switch does...coilgun.ru...those doesnt blow, so I guess yours wont neither ^^

 

[Leodahsan]

hahah sorry. I don't got experience but I try to have some knowledge and help others
I put the diodes there.. they wont seem a bad idea. Accidents happen u know. :eg:

 

[AnselmoFanZero]

Right...like I said: Dont wanna know what happens ^^

Might damage the charger as well...thats my main-concern.

 

[Leodahsan]

I think that putting diodes between the charger and the caps are a good idea.. just heatsink those and ensure they are >1000v RV capable
Not really expensive I say

 

[AnselmoFanZero]

Oo between charger and caps?
Needed for multi-stage...if you would connect all stages to the charger without the diodes, the first shot would trigger all stages.