Would like to increase curcuit capasity

[krypticnexus]

Hello all I have build up this curcuit and it works great but it only works with lower amperage fans like .2 or .4 amp. Well I have 1.2 amp delta fans I would love to use with this but I'm not sure what I need to do. I was thinking maybe a variable capacitor or something I'm really not sure. The 1.2 amp fans do run if you manually start them with your finger then it will continue to run.

Thanks everyone
Anthony

[Audioguru]

The IRFZ24 Mosfet can conduct 17A if you keep it cool or conduct 12A when it heats so that its case becomes 70 degrees C, when its gate to source voltage is 10V or more.
I think your NTC temperature sensor is not sensitive enough to cause Vgs to go to 10V or more. Try changing the  10k pot to a 100k pot.

[krypticnexus]

The IRFZ24 Mosfet can conduct 17A if you keep it cool or conduct 12A when it heats so that its case becomes 70 degrees C, when its gate to source voltage is 10V or more.
I think your NTC temperature sensor is not sensitive enough to cause Vgs to go to 10V or more. Try changing the  10k pot to a 100k pot.

ok ill be ordering new pots soon but do you think i should also change the ntc sensor to something more sensitive?

[jdraughn]

If I were you I would look into using PWM to drive the fan instead of running the mosfet in it's linear region constantly. Maybe use a 555 timer, or maybe someone can program and mail you a little 8 pin pic.