Cordless Drill - PC PSU please help


I want to drive my cordless drill motor with my Arduino. The motor must only drive in 1 direction. I think a H-bridge is not needed.
I want to use the PSU at 5V. I my test i saw a max of 5amp current flow.
Here are some pictures of my project.

I search for a NPN trans, and came on this one. Is this the right product???
I also want to know what kind of diode i must use.

Can anybody help me?
1- Is the tans the right one?
2- What diode (type) must i buy?



HI, thanks for youre reply!

I measured the locked motor at 5A, and operating current at 2A. So in youre opinion i must use a 20A or even better a 50A trans?

You say something easer to use...... Can you explain why this trans is difficult?

I searched for a trans with higher current and in the TO-220 package and found this one:
Is that a better one?

Hope to hear from you guys soon!


thanks for the information!!



That surface mount transistor also needs 0.5A base current to drive 5A out, so you'd need another driver transistor to drive it... Given you are running off a relatively low voltage supply I'd say a logic-level MOSFET is the way to go (a darlington transistor would soak up 1.5V or so and need a biggish heatsink and waste 10W or so).

A logic level MOSFET with a R(ds)on of 0.01ohm or less would be good - with a small heatsink. Be careful to select a logic-level device, most TO220 MOSFETs aren't logic-level. To be logic-level the R(ds)on will be quoted at Vgs=4.5V or at Vgs=5V.

At 5A it would dissipate 5x5x0.01 = 0.25W.

The diode needs to be able to take the current the motor takes, but only for a brief pulse. So a diode rated at 10A (pulse) or so should be fine.

Here is a logic level mosfet that can't be beat for $1.

Also avalible in module kit form:

That's good for 3A or so without a heatsink though, 0.01 ohms is a better spec and readily available.

thanks all!
I ordered the parts bij a dutch company Farnell.



Hi people,

i just assembled the parts together as in my scheme:

when i turn things on it works, but not perfect.
I measure a perfect voltage on the arduino pin 3, from 0V to 5V.
When i measure the motor voltage (5V circuit) i measure from 3,7V to 4,98V.
I don't understand when pin 3=0V why the motor recieves through the mosfet 3,7V.
Can anybody help me??



Sorry, i found it out allready.....
Switched the source and the drain...