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Registered Member #1774
Joined: Wed Oct 22 2008, 02:51AM
Location:
Posts: 135
Im trying to amake a variant of uzzors boost converter to charge the capacitors in my next coilgun. Mine is exactly the same except im only using the boost converter part and not the the "auto turn off" part. But it wont work with any of the MOSFETs I have, first I tried a 2sc2625 (400v 10amp N channel mosfet) but it draws about two Amps and only charges to 12v (then still draws 2 Amps and stays at 12v) while the mosfet slowly heats up, so I tried a c4106 (400v 7amp MOSFET) and it got upto about 12.6v before the MOSFET started melting the paint on my desk (I didnt realise it was doing this so I picked it up and now have a MOSFET shaped burn on my finger). Do I just need a better MOSFET? (Also note that the 555timer heats allot as well) If I just flick the powersuply on and off fairly fast it will slowly charge up to about 20v So i think the diode and inductor are fine.
Registered Member #1790
Joined: Fri Oct 31 2008, 10:10AM
Location: Sydney, Australia
Posts: 40
I think the problem is the 555 or the mosfet, but im preaty sure the 555 is blown aand is causing the mosfets to stay on.
Just rebuild the whole thing and make sure you connect everything correctly, and design it on a breadboard first than go to a vero board, in case you make another mistake.
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
I had the same problem. It was fixed by getting a better inductor (H value) vs the frequency. For the 555, add a resistor to the input, i had a 12v reg too.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
It is definitely something with the 555. The 555 is turning and keeping the mosfet on, so it is basically just shorting through the inductor. The output is 12 volts, because that is your supply voltage. The voltage goes up to 20 volts when you connect and disconnect the supply, is because it is working like the 555, just MUCH slower, charging and discharging the inductor, creating a slight rise in the voltage.
Registered Member #1774
Joined: Wed Oct 22 2008, 02:51AM
Location:
Posts: 135
Well i remade it on a proto board and now the 555 doesnt heat up but it still wont charge anything (current draw slowly increases past 3amps, which is my powersupply's max). so I tried another 555 I had not realising it was a 555p not 555n so it blew... Any other ideas or should I just go and buy another whole set of parts?
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Boost converter problems
