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Author Topic: Cordless Drill - PC PSU please help  (Read 783 times)
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Deventer
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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.
https://skydrive.live.com/?cid=418EF6310E888ECB&id=418EF6310E888ECB%21689&sc=photos
https://skydrive.live.com/redir.aspx?cid=418ef6310e888ecb&page=play&resid=418EF6310E888ECB!688

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
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Deventer
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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
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Deventer
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thanks for the information!!

Grtx,

Marcel
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Shannon Member
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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.
« Last Edit: July 30, 2011, 07:45:49 pm by MarkT » Logged

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

http://www.sparkfun.com/products/10213

Also avalible in module kit form:

http://www.sparkfun.com/products/10256
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Shannon Member
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That's good for 3A or so without a heatsink though, 0.01 ohms is a better spec and readily available.
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Deventer
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thanks all!
I ordered the parts bij a dutch company Farnell.


Gr,

Marcel
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Deventer
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Hi people,

i just assembled the parts together as in my scheme:
https://skydrive.live.com/?cid=418EF6310E888ECB&id=418EF6310E888ECB%21689&sc=photos

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

GRtx,

Marcel
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