Hi, I'd like to use an ST IRF740 MOSFET to flip a switch on a 24VDC motor.(http://www.datasheetcatalog.org/datasheet2/d/0j6qjdy97r1j3gwshsqhw2h4ek3y.pdf)Can i just hook the output up of the Arduino up to pin 1, ground to pin 3 and 24VDC coming through through the motor to pin2? I'd like the circuit to be as simple as possible. Anything else I need? I've seen some circuits out there but I'm unsure why they have more components.Thanks!
So what's the resistor for?A mosfet gate is like a large capacitor that has to charge up or discharge when first going from off to on and on to off, this draws high current for a moment and may stress the output pin current limit for the arduino output pin. Once the mosfet is fully on or off no gate current flows. So it's an arduino output pin protection thingee.Also, how do you get 10Volts to turn it on. The datasheet shows:VGS(th) Gate ThresholdVoltageVDS = VGS ID = 250 mA 2 3 4 V (3 volts typical)Am I missing something or is this the wrong spec point?Wrong spec to look at. Gate threshold is the voltage that the mosfet will just start to conduct current, perhaps just uamps. You need to look at the graph named "Output Characteristics" that plots current flow Vs gate voltage and you can see the almost no current flows with just 5vdc on the gate.Also look where they define what voltage is required for the best (minimum) Ron resistance:QuoteRDS(on) Static Drain-source On Resistance VGS = 10V ID = 5.3 A 0.48 0.55 ? A 'logic level' mosfet is required if one wants direct control from an arduino output pin.LeftyThanks
RDS(on) Static Drain-source On Resistance VGS = 10V ID = 5.3 A 0.48 0.55 ?
So what's the resistor for?
I think the gate-to-ground resistor is there to pull the gate low and keep it there unless something drives it high on purpose, to prevent accidental or unwanted switching. Could be wrong... but I seem to recall that's what it does.
Wiring is pretty much as you stated, except most recommend a series 100-150 ohm series resistor between that arduion output pin and the gate terminal. Also you need a common ground wire run between the 24 volt negative terminal to the mosfet source terminal and then on to a arduino ground wire.Lefty
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