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Driving a large stepper motor

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Junior Member level 1
Oct 25, 2005
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large stepper motors

i need to drive a large stepper motor for something i`m working on.....its considerably larger than the ones used in printers. takes 1.8° per step.
I've always used a ULN2003 ic to drive stepper motors but i've never driven something as large as this. i tried using ULN2003 to run works but the ic gets very hot very quickly.

Anybody knows how to drive a big stepper motor????? Its really urgent 'coz i need to submit that something to somebody quite soon. Help me out guys.

One other thing.....the motor runs very slowly....takes 5 secs to complete one revolution. Do all stepper motors with small steps run that slow???

large stepper motor

use 4 TIP122 transistor insted of ULN2003.
speed of rotation depend on number of pulse per second (pulse frequency), you can increase frequency.

big stepper motor

Check the motor spec and select some appropriate transistors (MOSFETs).
Do a power loss calculation to see if and what heatsinks are necessary.

As for the speed, you just need to increase the frequency of the steps.

tip120 stepper

i tried increasing the number of steps but beyond 40 pulses per seconds the torque starts to gets really low.....i want to drive the motor at higher speed with substantial torque.

tip120 stepper motor

For optimum performance you must use current drive, insted of voltage drive.
because of inductance effect of motor winding, current [& torque] reduced in higher frequency.

stepper motor open source

**broken link removed**

try here for a list of ic's made to do the job
properly without the need to drag the calculator out !!

just one page from many many dedicated ic's makers
who have draged it out before too many times

i used this google search string

4x tip 122 LOL hahahahaah hehehe max freq 1.5khz then BANG goes your darlingtons

stepper motor large

Mr. hahahahaah hehehe
it seem you are very professional.

sepper motor drive with tip 122

switching time for darlingtons is too slow

need for fets here

sry wasnt taking the piss :|

however for ac {audio freq} they are fine

as used in many cb radios as a rf final and/or driver stages
dc supply rail modulator

yet to see it driving pwm


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stepper motor using tip120

do u know how to use these ic's. I mean i'm the worst of novices so i need help in this too. I've never driven a stepper with anything except darlingtons. How do u use these ic's. They look complex. I had a look at A3983 datasheet and couldn't get hold of anything though i guess they are supposed to be easy to use.


Hey Davood
If u can sketch a quick ckt using TIP120/121/122 to drive a six wire (2 common) motor and upload it i'll be really grateful.

look guys! i may be looking like an idiot to u right now but i'm desperate. Pleeeeeeeeeeease help me out.

and by the way
is a six wire motor bipolar or unipolar???
i think this question ought to clarify how weak i am at steppers!!!!!

using a tip120 to drive a stepper motor

any fet driver bridge can be used to drive this motor
provided it can sink enought current and gives a good range of torque

chips like the more complex ones you mention have other features

it was ment as a general example of availible kit
i also posted the google search string for the purpose of finding a better example

i know how to use / model / allign / build / etch / process / dream up /
ic's of any kind from many years of doing it all the time

one day youll learn enough by reading and working in this field and
youll click how its done

if you look on the label on the motor
then type the part number into google you will get the datasheet

or far more info
both types of motor can have up to 8 wires

so poor choice of question

uln2003 stepper m+ wire

Hey Davood
If u can sketch a quick ckt using TIP120/121/122 to drive a six wire (2 common) motor and upload it i'll be really grateful
previusly you said

i tried using ULN2003 to run works but the ic gets very hot very quickly.

just you can use one TIP122 in place of each internal transistor of ULN2003.
6 wire motor (2 common) needed 4 transistor.

For higher current you can use smaller resistor insted of 2.2K (eg. 470 ohm).


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stepper transistor 4 wire

l297 & l298
for more detal see their datasheet

large diameter stepper motor

a lot depends on how much current the stepper's coils draw. In general, bipolar transistors don't work well for higher current devices. Also, the answer depends on whether you have a bipolar or unipolar stepper (4 wires or more than 4 wires). Check this site for a lot of open source controller designs: There are a number of good ones there.

Note that to get more power, you should go to a higher voltage than on the label. This is ok if you keep the current at the rated level. There are 2 ways to do this: power resistors or PWM (chopping). PWM is much better. You can often go to 10X the voltage rating with no ill effect and a lot more torque.



good discussion. but here is also another schematic about TIP120.
taken from . Here why the diodes are used. And what is the ratio of resistors with current.

I have used the above diagram and TIP 122

My stepper is 2.5v motor

It is working. Thank u Geniuses!

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