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Topic: MOSFET use for driving larger current devices (Read 554 times) previous topic - next topic

taz3m

Dear all,

I would like to raise one confusion upon the connection of a MOSFET to my arduino UNO board.

This confusion aroused after reading some Arduino materials.

My concern:

I have a fan with operating voltage 5Vdc but alas with current consumption 0.16 Amps.

In regards to an output Pin on the Arduino, we can draw up to 20 mA per pin and a total of 200mA in total. correct if im wrong.

Can i supply my Arduino Board with my external Power supply 9 Vdc, and take my supply from Vin of my board, pass through coresponding resistances through my MOSFET and up to my FAN without hurting my Arduino ?? Please note that i will like to control my FAN with PWM in relation to a thermistor.

thanks

Regards
taz
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tz
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MarkT

Basically yes - be sure it's a logic-level MOSFET (that can be switched with 5V logic - most require 10V).  The 5V fan might run a bit fast on 9V - so you are adding a resistor to drop the voltage a bit?  You would normally do that on the high side, and switch with a n-channel MOSFET or NPN transistor on the low side.

Is the fan a brushless motor BTW?
[ I won't respond to messages, use the forum please ]

dhenry

Quote
current consumption 0.16 Amps.


That's like nothing. A puny to92 npn or 2n700x will handle that with ease.

fungus


Can i supply my Arduino Board with my external Power supply 9 Vdc, and take my supply from Vin of my board, pass through coresponding resistances through my MOSFET and up to my FAN without hurting my Arduino ?? Please note that i will like to control my FAN with PWM in relation to a thermistor.


Basically, yes, but make sure it goes through the fan before it goes through the MOSFET...

No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

taz3m


Basically yes - be sure it's a logic-level MOSFET (that can be switched with 5V logic - most require 10V).  The 5V fan might run a bit fast on 9V - so you are adding a resistor to drop the voltage a bit?  You would normally do that on the high side, and switch with a n-channel MOSFET or NPN transistor on the low side.

Is the fan a brushless motor BTW?


I need to check if the MOSFET is a 5 level logic - i got the tech spec for the mosfet bt got to read it .. :) but im pretty sure its a 10 V logic. .

Yes wanna use the resistor to drop the voltage a bit. about the circuit it seems  i will need an NPN transistor ?

What if . . Can i achieve the same with an SSR?? And i already have that at hand, with 5 volt logic and switch up to 250 vac . . can i run the FAN without the need to get an external 5V power supply for the FAN, can i use the 9 Vdc . .

Concerning the FAN, i got them from the real china market, no specs at all, with brand name RUNDA without model no :-( i need the cfm as well for some sizing work bt . . :(

But still i will like to control these through pwm with my arduino without hurting my pins, . . .

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tz
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taz3m


Quote
current consumption 0.16 Amps.


That's like nothing. A puny to92 npn or 2n700x will handle that with ease.



Are you refering to transistor type ???
tz
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oric_dan

You never want to try and drive loads other than a few mA from the
Arduino pins. Always think about using a driver inbetween, like an NPN
inverter or mosfet.

Personally, I try not to connect large loads to the same power supply as is
powering the Arduino bd. Especially true if the load is a motor or other
inductor or R/C servo, as they will inject a lot of noise on the power buss.

I do sometimes power my robots, walkers and motorized, from the same
battery, but I always add additional electrolytic and bypass caps across the
power busses.

Another thing people use is called a "brownout circuit" on the Arduino bd
Vin pin. This is basically a diode/large capacitor circuit so the capacitor
temporarily powers the Arduino v.reg if the Vin voltage sags. Of course, in
this case,  you don't want the load connected to the Vin pin on the header.

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