small, battery powered stepper motor

[[email protected]]

I am looking to use a basic stamp controlled (with a ULN2003 chip)
stepper motor in a small (pocket sized), battery powered prototype. it
doesnt need much torque at all. the problem is i dont know much at all
about stepper motors...specifically which one to use.

i need it to be battery powered (a small battery) and cheap. i was
thinking something along the lines of a NAMA 17. it needs to draw
power from a small battery...maybe as big as a standard 9 volt but
hopefully smaller (any ideas?).

http://www.eettaiwan.com/ARTICLES/2002MAR/PDF/2002MAR08_AMD_MPC_AN81.PDF
is the basic setup i'm going to be using...except with a smaller basic
stamp board.

any help or suggestions would be VERY much appreciated. i'm looking to
get it done soon as my opportunity to use (for free ) the Rutgers
University SLA rapid prototyping machine will be gone shortly. you may
post suggestions here or email me at [email protected].

much thanks,
adam

 

[BobG]

One problem with stepper motors is that one coil is always on.... a
'trick' to reduce the holding current is stick an R in series with
each coil. Use 4 outputs... a pair for each coil... energize coils
like this to go one way... 01 01, 01 10, 10 10, 10 01, and back to 01
01.

 

[[email protected]]

One problem with stepper motors is that one coil is always on.... a
'trick' to reduce the holding current is stick an R in series with
each coil. Use 4 outputs... a pair for each coil... energize coils
like this to go one way... 01 01, 01 10, 10 10, 10 01, and back to 01
01.

my plan was to actually remove the current after each desired sequence
of movement as there will be something to hold the motor in its
position. i only need it to move a certain amount of degrees then
stop...i have a mechanical break or holding mechanism.

 

[Sjouke Burry]

my plan was to actually remove the current after each desired sequence
of movement as there will be something to hold the motor in its
position. i only need it to move a certain amount of degrees then
stop...i have a mechanical break or holding mechanism.

If you bridge the resistor with a capacitor,
you get a powerful step response, without to
much coil heating, and a useful holding force.
Just design the cap value such that at the
maximum step speed, the voltage on the resistor
has dropped to about half of the start value, and
the resistor value for an acceptable hold force.

 

[[email protected]]

does anyone have a suggestion for a small, slow, relatively
inexpensive, low torque, low voltage and able to be powered by a small
battery stepper motor?

 

[BobG]

does anyone have a suggestion for a small, slow, relatively
inexpensive, low torque, low voltage and able to be powered by a small
battery stepper motor?

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There are lots of them listed on Jameco, for example. I'd say, the
higher the coil ohms the better for battery operation.