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Basic stamp, stepper and 'muscle wire'

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Baldilocks

New Member
Hi, I've been out of electronics for about 10+ years and have gone a little rusty!

I want to use my basic stamp kit (I've got quite a lot) to run a small stepper, then use it to operate a length of Nitinol. The project is to measure out accurate lengths of magnesium ribbon using a stepper, then cutting it with a Nitinol actuated cutter (scissors!).

I believe that I can drive a power mosfet (diode protected) directly from the stamp, and the stepper directly from the mosfet. The only additional components are a couple of resistors - a few 10s of k in series with the gate and a meg or so from gate to drain to protect from static.

Picbits have a IRF540 28A 100v at 25p which look good to me for both the stepper and the wire. They also have a 24v 0.6A stepper which might be OK (I don't particularly want to use 24V - I work in a school and 12V is much more accessible.)

Mosfet link

Stepper link

Has anyone got any comments?
 

Grossel

Well-Known Member
In my opinion, the transistors is overkill. You don't need that powerful transistors. But no worry - it will work.

The stepper will probably run well with only 12V, but maximum torque will be greatly reduced. That will affect acceleration and max speed.
 

Baldilocks

New Member
Thanks Grossel. I recognise that the Mosfets are over-specced, but they are cheap!

At a theoretical level would there be any advantages/disadvantages between, say, a 10A 50V mosfet and a 20A 100V one?

Ian
 

Grossel

Well-Known Member
Thanks Grossel. I recognise that the Mosfets are over-specced, but they are cheap!
:)

At a theoretical level would there be any advantages/disadvantages between, say, a 10A 50V mosfet and a 20A 100V one?
The latter one may be physically bigger. It also might have a slower response time, but that's might not be true (see datasheets).
 

Mr RB

Well-Known Member
I would consider using a ULN2003 or ULN2004 darlington chip. They are great for driving those little stepper motors at a few hundred mA and much easier to contruct than 4 separate transistors.
 
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