Mosfet not letting amps through?

[Nestorpants]

Hey everyone,

I built my first box mod this week and used the basic mosfet setup however, I ran into a strange problem and I've searched around but I'm stumped. The mosfet is allowing voltage to go through to the 510 connector but it's limiting the amps to between .02 and .05 amps therefore the atty doesn't fire. I have proper amps going into the source pin but not coming out of the drain pin.

I've tried three different mosfets so far with the same issue. I have one NTE2987, one NTE 2395, and an IRF510 that was from a different project.

This is the schematic that I'm using:



Only difference is I'm just using a single 18650. Like I said I am totally lost so any input is appreciated.

 

[johanct]

It seems from your description that the mosfet doesn't fully switch on, make sure that the mosfets you use are Logic Level types - standard mosfets require way more than 4.2V to fully switch on.

 

[Uncletattoowhat]

The diagram clearly shows the Mosfet that has been proven time and again that it works for the application.

IRLB3034PBF International Rectifier | IRLB3034PBF-ND | DigiKey

 

[Nestorpants]

I have some of the irlb3034's coming in the mail so hopefully that solves the issue. But I'm still curious as to how and why my mosfets are able to send voltage to the atty but no current.
The NTE2987 is a logic level mosfet that turns on with 2.5v and has an ID of 20 amps so there must be another parameter that makes the 3034 work but not this one. I'll compare the spec sheets tonight and see if I can figure anything out.

 

[Bunnykiller]

not too sure about this, its been a couple of years since Ive messed with mosfets... but the source and drain should be on the + side of the battery and gate tied to ground????

 

[Bunnykiller]

did you insert the 15K ohm resistor on the gate? you may need to go to a lower ohmed resistor ehhh 10K maybe even 5.1K

 

[Bunnykiller]

on IGBT's ( a more impressive mosfet) requires the gate to be driven low ( negative) to turn off and in the on position, a limited amount of voltage is applied with enuf current to keep the S/D working. You may need to create a voltage divider to supply the proper voltage to the gate....

 

[Bunnykiller]

heres a link that may help

http://www.vishay.com/docs/91015/sihf510.pdf

 

[Visus]

The 2987 should be golden it has lower IR (less sag)than the 3034 I would try another resistor fer sure but 15k should be golden..
Thats a good one if ya can get er runnin properly. Its also very easy to statically blow them out so you may have blew it out without even knowing..