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It's a very small stepper at 18 ohm resistance per coil(2 of them) (4 phase).

enter image description here

I got: stepper in the picture, L9110, LM358, arduino.

I used an L9110 with the arduino. The stepper moved where it was supposed to move but with a lot of noise, vibrations during some frequencies. At higher frequencies it moved very smooth but at lower frequencies it became a clock. "tick", "tock", "tick", "tock".

I want to step with a sine wave signal. I want it to have an amplitude of 3V. How do I make such a circuit?
3 V / 18 ohm = 0.16 A
3 V * 0.16 A = ½ watt

My previous ideas that have failed:

  • Use two pins (filtered pwm) on the arduino.
    Fail: they can only give 20 mA safely. (18 ohm * 20 mA * 20 mA = 0.0072 watt). Too weak.
  • ^Use above idea with two LM358 as buffer for the two pins.
    Fail: LM358 outputs about 1 mA (0V gnd, 5V vcc).
  • Use a linear analog voltage regulator.
    Fail: It will be ineffecient and I don't have a linear analog voltage regulator. Though I could buy one.
  • Use L9110.
    Fail: It only has a truth table. There's no analog voltages.

Since it's just a very small stepper that won't use more than ½ Watt I should be able to get away with a few components.

When it comes to software and digital things I'm a king. When it comes to analog circuits I'm a peasant. Please help this peasant you analog kings and queens.

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    \$\begingroup\$ Combine the first bullet with the last one. Feed it PWM through a driver (no filtering should be needed if the frequency is high enough). \$\endgroup\$
    – Eugene Sh.
    Aug 4, 2015 at 18:27
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    \$\begingroup\$ H-Bridge + PWM = Stepper motor driver. \$\endgroup\$ Aug 4, 2015 at 18:40
  • \$\begingroup\$ @TomCarpenter So no filtering? Won't this produce sound? If I use filtering will it cover the ½ watt? \$\endgroup\$ Aug 4, 2015 at 19:08
  • \$\begingroup\$ @EugeneSh. "Bullet", is that the LM358? \$\endgroup\$ Aug 4, 2015 at 19:08
  • \$\begingroup\$ Depends on the PWM frequency. There comes a point when the inductance of the motor winding will act as a filter and smooth out the PWM signal. There is a limit to how high you can go which comes down how fast the transistors in the driver can switch - if you switch them too fast you can end up with both high side and low side on at the same time resulting in a lot of heat dissipation in the driver. \$\endgroup\$ Aug 4, 2015 at 19:21

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Apparantly what I need is called a Push-Pull Amplifier.

This is the schematic that I made and decided to go for. In case anyone cares.

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