hi
would it melt if it was too thin ?
I doubt it. What the circuit does it charge a capacitor (5000uF) and then this is shorted through the coil via the SCR. The discharge will be very quick, and some of the diodes will prevent oscillation (also known as 'ringing') where the energry is dumped into the coil, from the cap, and then the coil dumps some energy back into the cap...just like an LC circuit.
The discharge will be very quick, under a ms. But....if you were to use a massive capactior and some very thin wire, there is a small chance the wire in the coil could explode. You're ok with a 5000uF cap.
does the diameter of the coil have to be at certain
ammount or any diameter would do the trick ?
I don't think there are any 'rules', you're just creating a massive magnetic field for a very short period. I'm unsure of how you are going to 'eject' your seat? Most coil guns, have a projectile placed just outside the coil, when the coil is enegised, the projectile it strongly attracted to the centre of the coil, but the pulse has stopped by the time it gets there, so it just goes through the coil, and out the other end.
Some designs, that can be more efficient, use the Lorentz force. Put simply, any coil nearby your coil, will have a current induced in it, of opposite polarity. If this secondary coil is closed (like a ring of aluminium) then current will flow in it, producing its own magnetic field.....which again, is opposite to the first coils polarity....the effect? They repel like theres no tomorrow
Also, because the secondary coil is simply a 'ring' (a single turn on a transformer) the voltage from the first coil is stepped down....by *1st coil turns : 1* And the current is stepped up. Because magnetic field strength is determined by current flow, this makes the effect quite impressive.
Anyway, I'm just ranting now....sorry, back to your problem.
The coil would simply require experimentation. From school, the properties of a coil that determine field strength are:
-Diameter of wire (you want it fairly thick)
-Some sort of 'core' (iron probably, or some sort of ferrite material)
-Number of turns in the coil
And obviously current. You might not want to have too many windings....more windings = higher resistance = less current flow. But anything under 500 turns should be OK.
Hope this helps, at least in some way :/
Finally, your SCR. I'm sure it will be fine, but I built a 'pulser' a while back, very similar design to yours...used for Xenon Tubes, Coil guns, rail guns etc.. And the SCR nearly always 'latched'. That is, once fired, the SCR remained 'on' and could not be turned off. It was rated at 800v and peak of 120A. Think I blew it.
If you want a substitute SCR....check the
max Voltage, and
peak current. It won't be conducting all the time, so av. current is meaningless.
Regards,
BuriedCode.