Cordless Drill - PC PSU please help

Other Hardware Motors, Mechanics, Power and CNC
1

Hi,

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???
http://www.nxp.com/documents/data_sheet/PBSS4021NX.pdf
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?

Thanks,

Marcel

2

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: http://www.nteinc.com/specs/300to399/pdf/nte331.pdf
Is that a better one?

Hope to hear from you guys soon!

Thanks

3

thanks for the information!!

Grtx,

Marcel

4

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.

5

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

Also avalible in module kit form:

6

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

7

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

Gr,

Marcel

8

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??

Thanks,

Marcel

9

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

GRtx,

Marcel