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berkie

homemade mosfet starts shooting after a while

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I made a mosfet following terry's design from unconventional airsoft and tested it about a week ago. the first day everything went fine, but the second day te FET tripped while briefing was going on and the selector was on safe. I quickly unplugged the battery adn after a minute plugged it in again. it didnt instantly start shooting but after a minute it began again.

 

 

 

Because of this I don't believe I have a faulty fet but im unsure what it could be.

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what spec mosfet are you using?

 

I have the 3034s, and they take solder heat really well [precautions taken of course] and never had any die on me yet/or my customers.

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That is reallllly strange, are you using Extreme-Fire's schematic or Gologo's design?

 

 

Extreme fire schematics. I followed the airsofttutorials tutorial which is the same minus the diode. that one I added myself following extremefire's build.

 

Ill open it up later tonight for pics and will check for a broken insulation.

 

It could be the selector wiring. I used wires from adata or network cable, which is smaller than 20 awg and is regular copper.

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Check the soldering on the 2 prongs.

 

if its even touching the GB's walls, it could create a short. Check with the GB closed and test the motor/trigger pull. etc. Follow the steps from function to not functional. Error analysis that stuff.

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Check the soldering on the 2 prongs.

 

if its even touching the GB's walls, it could create a short. Check with the GB closed and test the motor/trigger pull. etc. Follow the steps from function to not functional. Error analysis that stuff.

 

The entire mosfet is covered in a big shrinktube so I think it's somewhat impossible for that to happen, and both prongs are seperately covered in shrink tube underneath.

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The key factor is that its happening a minute or two "after" the battery is connected. If it was a short it would instantly fire when you connect the battery.

 

I am surmising you have a low grade component in there somewhere and after it has been connected to the battery it's heating up and then forming a circuit.

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The key factor is that its happening a minute or two "after" the battery is connected. If it was a short it would instantly fire when you connect the battery.

 

I am surmising you have a low grade component in there somewhere and after it has been connected to the battery it's heating up and then forming a circuit.

 

 

That might possibly be it. I'm not sure if the big Diode works that way, but that's the only thing I've ordered from Ebay. The resistors come from a friend who works with X ray machines and the mosfet itself comes from a reputable dutch store. I'll try it out and when it trips I'll check the temperatures.

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