problems with a mosfet
Archiver
Posts: 46,084
I am useing an n channel mosfet (International Rectifier irf730) to contorl
a fan, in my circut i have conected the gate to the stamp pin an a pull down
resistor, the sorce to ground and the fan to the dran to the neg of the fan
and positeve to +12vdc. i also put a diode reverced acros the fan to stomp
any voltage transenats. both +5 and +12 have the same gnd.
my problem is that i can control the fan, even if i tie the gate directly to
+5v or gnd, the fan just runs at about 50% and the mosfet really heats up,
is the fet fried? the gate threshold according to the data sheet is 2 to 4
volts. whats the deal?
Lincoln
a fan, in my circut i have conected the gate to the stamp pin an a pull down
resistor, the sorce to ground and the fan to the dran to the neg of the fan
and positeve to +12vdc. i also put a diode reverced acros the fan to stomp
any voltage transenats. both +5 and +12 have the same gnd.
my problem is that i can control the fan, even if i tie the gate directly to
+5v or gnd, the fan just runs at about 50% and the mosfet really heats up,
is the fet fried? the gate threshold according to the data sheet is 2 to 4
volts. whats the deal?
Lincoln
Comments
>I am useing an n channel mosfet (International Rectifier irf730) to contorl
>a fan, in my circut i have conected the gate to the stamp pin an a pull down
>resistor, the sorce to ground and the fan to the dran to the neg of the fan
>and positeve to +12vdc. i also put a diode reverced acros the fan to stomp
>any voltage transenats. both +5 and +12 have the same gnd.
>
>my problem is that i can control the fan, even if i tie the gate directly to
>+5v or gnd, the fan just runs at about 50% and the mosfet really heats up,
>is the fet fried? the gate threshold according to the data sheet is 2 to 4
>volts. whats the deal?
>
>Lincoln
>
>Lincoln -
What is the amperage rating of the fan ?
Bruce Bates
Sounds like the fan is either defective (too much current required), the
RON of the MOSFET is too high, or as you say the FET is defective. If
the fan is OK (check it directly connected to a 12 v supply, and measure
the current draw). You could try multiple MOSFETs in parallel, to reduce
RON. My preference is the IRF540 device.
Rob
Original Message
From: Bruce Bates [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=UglMumXfbG0tfDMKqioCgIGKKouBLH17uZYZjSEJQw-52ITMsk4LmTq2-rbhQ71Q0VH5UCdscNS_X7pMZM3t]bvbates@u...[/url
Sent: 20 March 2002 04:58
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] problems with a mosfet
At 08:47 PM 3/19/2002 -0800, you wrote:
>I am useing an n channel mosfet (International Rectifier irf730) to
contorl
>a fan, in my circut i have conected the gate to the stamp pin an a pull
down
>resistor, the sorce to ground and the fan to the dran to the neg of the
fan
>and positeve to +12vdc. i also put a diode reverced acros the fan to
stomp
>any voltage transenats. both +5 and +12 have the same gnd.
>
>my problem is that i can control the fan, even if i tie the gate
directly to
>+5v or gnd, the fan just runs at about 50% and the mosfet really heats
up,
>is the fet fried? the gate threshold according to the data sheet is 2
to 4
>volts. whats the deal?
>
>Lincoln
>
>Lincoln -
What is the amperage rating of the fan ?
Bruce Bates
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject
and Body of the message will be ignored.
Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
thanks
Lincoln
Original Message
From: "Rob" <robbed666@b...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, March 19, 2002 11:19 PM
Subject: RE: [noparse][[/noparse]basicstamps] problems with a mosfet
> Hi
> Sounds like the fan is either defective (too much current required), the
> RON of the MOSFET is too high, or as you say the FET is defective. If
> the fan is OK (check it directly connected to a 12 v supply, and measure
> the current draw). You could try multiple MOSFETs in parallel, to reduce
> RON. My preference is the IRF540 device.
>
> Rob
>
>
>
Original Message
> From: Bruce Bates [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=ArgFPN7jBD0mhm8X0kFxbRQAH6Zxa4Tg7paD3Tpj7Cfz9ECsHW6WGIqNS2_-c8zg7omz2YhWO5AKmMw3Kw]bvbates@u...[/url
> Sent: 20 March 2002 04:58
> To: basicstamps@yahoogroups.com
> Subject: Re: [noparse][[/noparse]basicstamps] problems with a mosfet
>
> At 08:47 PM 3/19/2002 -0800, you wrote:
> >I am useing an n channel mosfet (International Rectifier irf730) to
> contorl
> >a fan, in my circut i have conected the gate to the stamp pin an a pull
> down
> >resistor, the sorce to ground and the fan to the dran to the neg of the
> fan
> >and positeve to +12vdc. i also put a diode reverced acros the fan to
> stomp
> >any voltage transenats. both +5 and +12 have the same gnd.
> >
> >my problem is that i can control the fan, even if i tie the gate
> directly to
> >+5v or gnd, the fan just runs at about 50% and the mosfet really heats
> up,
> >is the fet fried? the gate threshold according to the data sheet is 2
> to 4
> >volts. whats the deal?
> >
> >Lincoln
> >
> >Lincoln -
>
> What is the amperage rating of the fan ?
>
> Bruce Bates
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject
> and Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>