hi all i need a help

[zamir89]

im trying to drive this 5v 2a stepper motor using tip 122 transistor ....after the connection the motor drive but the torque is not high enough as i can easily stop it using my hand....the resistor im using is 0.4ohm should i use 1Kohm as in this diagram so the motor will operate at high torque?

[raschemmel]

What is the motor supply  ? (hint: arduino +5V is not a correct answer to this question)

ALSO - PLEASE STATE YOUR KNOWLEDGE OR EXPERIENCE WITH ELECTRONICS.

[Robin2]

Is that a 5-wire or 6-wire stepper?

If it is a 6-wire stepper just ignore the two centre wires (keep them separate from each other and everything else) and treat the motor as a 4-wire bipolar stepper. Then just get a proper stepper motor driver board and save yourself a lot of trouble. I would get a 3amp driver board to give a bit of headroom.

The main shortcoming with your design is that you can't use high voltages because you have no current limiting circuitry to prevent overloading the motor.

...R

[Grumpy_Mike]

the resistor im using is 0.4ohm

You sure of that!
That would mean you are overloading the arduino output pins. It won't affect the motor but it might fry your arduino. Stick with 1K.

[raschemmel]

@Robin,
Here we go again...

@OP,
Can you  post a vendor link or datasheet for your motor ?
Where is your code ?
What is your motor power supply ?

[MarkT]

im trying to drive this 5v 2a stepper motor using tip 122 transistor ....after the connection the motor drive but the torque is not high enough as i can easily stop it using my hand....the resistor im using is 0.4ohm should i use 1Kohm as in this diagram so the motor will operate at high torque?

The diodes are in the wrong place, they go anode to collector, cathode to +ve motor
supply.  You have possibly blown something.

You'll need ~6.5V supply to get to about 5V to the motor, since darlingtons drop lots
of voltage at high current.  And enough amps in the power supply.

[raschemmel]

Do you know how to test the TIP122? (put the diods across the motor windings as suggested. cathode to +V_motor , anode to Collector)

[zamir89]

err..im using a standard 5v 2amps adapter...u guys mean the diodes connection are wrong?

[Grumpy_Mike]

Yes they should be between the collector and the motor supply.

[zamir89]

humm thanks all i think this is the limit this motor can go....if i use a higher supply it may damage the coils

[Robin2]

humm thanks all i think this is the limit this motor can go....if i use a higher supply it may damage the coils

Did you read Reply #2?

...R

[zamir89]

hmm buying a proper driver...nah i already owned a big easy driver i decided to make own driver

[raschemmel]

Did you measure the resistor Mike asked you about ? Is it really 0.4 ohms ?
You never posted your code. You never posted a photo of your circuit. You never posted any measurements for the TIP122s.
I really don't see how you can draw any conclusions on your own, considering the circuit was miswired to begin with, the resistor value you claim to be using doesn't match the schematic you posted, and we still haven't seen your code.

[Robin2]

hmm buying a proper driver...nah i already owned a big easy driver i decided to make own driver

Then I will happily leave you to your masochism.

Would you mind going back to your original post and changing the title to something more meangingful so that I know to avoid it.

...R

[MarkT]

Absolutely, subject lines are there to identify the subject of the posting so those with
the right expertise can find relevant threads to contribute to.  We can all work out
someone posting here is wanting help with an Arduino project!