I've just thrown together a schematic for a motor controller that should switch a motor on and off from the 5v signal from a micro-controller and should also allow for manual override via a switch; could people please point out any obvious issues with it before I build it in Veroboard?

The main issue I want to cover before implementing this is, is there some sort of rough guide for the resistor values? One of them is current limiting to protect the mosfet and the other is a pull down; is there a suggested size for these and will the ratio between the two effect the performance at all?

My other question surrounds the mosfet; am I right in thinking that the mosfet gate behaves like a capacitor in that it charges up until it saturates and then the channel between source and drain is fully open?

That should cover it so cheers for any help .

Many thanks
Oddy

 

The IRFZ44N is not a logic level FET. If motor is low current, less than 5 A, you might get away with only 5 V gate V. You could use a non inverting buffer , VCC 9V, 5V input, maybe a NPN & PNP pair?

 

Ah, dang, would it be possible to drive it via a transistor and a higher voltage source? i was hoping to control a 10amp motor so I may just hunt down a logic level mosfet.

 

If you are stuck with 5V input then a non inverting buffer is no big deal & you'll have 9 V for drive, which is plenty for 10 A output. Might add a diode across motor, cathode to VCC.

 

Just your basic, "double invert" circuit.

 

IRL530? Digikey $1.50.
Max.