Creating a Post Consumer Life & Homestead in
Truth or Consequences, New Mexico. Making Our Own Fuel, Power, Food & Medicine, Building Materials and Domestic Goods since 2006.
I've been doing some bread board prototyping for a microcontroller based battery desulfator unit. At this point I am heating up a inductor or the mosfet both of which are BAD. I think my pulse is inverted so I'm working on fixing that today.
I think you are definitely going to keep burning mosfets with the schematic you posted earlier. The P-channel mosfet is probably not turning all the way off due to the 5V output from the avr being way below the fully off voltage (the source voltage). I would hook up a 2n3904 to switch the 12V from the source side of the transistor. Take a look at this h-bridge schematic: http://www.cadvision.com/blanchas/hexfet/npch-sw-sch.htm I am pretty sure your mosfet is dissipating quite a bit of heat when it is supposed to be off. If I understand your circuit (I am a little rusty), this will add the bonus change of turning the transistor ON when your output is high from the avr, which should make the program a little simpler :)
4 comments:
Don't let the magic smoke out!
I think you are definitely going to keep burning mosfets with the schematic you posted earlier. The P-channel mosfet is probably not turning all the way off due to the 5V output from the avr being way below the fully off voltage (the source voltage). I would hook up a 2n3904 to switch the 12V from the source side of the transistor. Take a look at this h-bridge schematic:
http://www.cadvision.com/blanchas/hexfet/npch-sw-sch.htm
I am pretty sure your mosfet is dissipating quite a bit of heat when it is supposed to be off. If I understand your circuit (I am a little rusty), this will add the bonus change of turning the transistor ON when your output is high from the avr, which should make the program a little simpler :)
Rantenki - Thanks for the N2N3904 transistor tip. I have dug one out of my electronics stash and will give it a try in combination with the p-fet.
No problem! Let me know if it works. I love the idea of getting a little more life out of the lead acid cells.
Post a Comment