Airsoft Canada

Go Back   Airsoft Canada > Discussion > Doctor's Corner
Home Forums Register Gallery FAQ Calendar
Retailers Community News/Info International Retailers IRC Today's Posts

MOSFETS overheating

:

Doctor's Corner

Reply
 
Thread Tools
Old January 23rd, 2008, 19:10   #31
WingZER0
 
Join Date: Dec 2002
I just remembered something that completely slipped my mind. Some time ago the 249 burned out it's fuse when I was running a 7.2 1700 mAH battery when it was still stock wired. That was right before I began rewiring for a MOSFET.

It was a 30A fuse IIRC.... would this have any bearing?
WingZER0 is offline   Reply With Quote
Old January 24th, 2008, 00:33   #32
green_ninja
 
green_ninja's Avatar
 
Join Date: Apr 2007
Location: Winnipeg
Send a message via MSN to green_ninja
Re. heatsink

Quote:
Originally Posted by mcguyver View Post
Mnay FETs will heat up horrendously under load, even a small load. A heatsink is the solution, to increase the effective mass and surface area of the FET when.....
....specify whether you had a fuse in the system, but if you had one it likely would have blown already or shown signs of thermal damage.
I tried making a mosfet for myself, but to order the mosfet semi-conductor itself, you can only buy them in bulk (like 1000's). Screw that, so I found hhairsoft to make me one. Turned out to be a very efficient and sleek design, but after reading how these buggers like to heat up, I modded it with a heatsink from a useless videocard. It also helps to put a bit of thermal grease between the mosfet and the sink. Turned out great, and works fine!



FET increased my ROF by 27% from 840rpm to 1140rpm w/ no major sign of heat after full auto of 10-15 sec, running w/ 9.6v battery; at ~340fps w/ .20g. Do the heatsink if you get mosfet! highly recommend.
__________________
LOL

Last edited by green_ninja; February 5th, 2008 at 14:52..
green_ninja is offline   Reply With Quote
Old January 24th, 2008, 00:38   #33
mcguyver
 
mcguyver's Avatar
 
Join Date: Aug 2005
Location: Northern Alberta
The best compound to get would be some heatsink compound. I don't know exactly what's in it, but it's white and uber-sticky, great for transferring thermal energy. Even a small heatsink is a huge benefit. Look at the metal back on a TO-220 size FET and see how little surface area and mass is there, for passing so much current.
__________________
Age verifier Northern Alberta

Democracy is two wolves and a sheep discussing what's for dinner.

Freedom is the wolves limping away while the sheep reloads.

Never confuse freedom with democracy.
mcguyver is offline   Reply With Quote
Old January 24th, 2008, 00:47   #34
green_ninja
 
green_ninja's Avatar
 
Join Date: Apr 2007
Location: Winnipeg
Send a message via MSN to green_ninja
Yes, that's what I used, same sh!t from underneath the CPUs, works great eh?! yeah, there's direct contact b/w the metal backing of my mosfet and heatsink, should have better heat dissipation.
__________________
LOL

Last edited by green_ninja; February 4th, 2008 at 11:40..
green_ninja is offline   Reply With Quote
ReplyTop


Go Back   Airsoft Canada > Discussion > Doctor's Corner

Bookmarks


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Airsoft Canada

All times are GMT -4. The time now is 06:14.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.