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I apologize if I'm asking a really simple/stupid question here, or if this is an xy problem and I'm missing something entirely. I'm someone working way outside my field here since electrical systems and especially power supplies are not anywhere close to my usual area of work.

I'm currently tasked with developing a system that is mounted on a drone. Driving this system is a stepper motor which is controlled by an Arduino Nano. The problem I'm running into, however, is that in order to keep the weight down because drones, I have to use a PM-stepper motor compared to the much heavier hybrid stepper motors.The voltages of the motors I have access to are either 24V or 15V, but then the weight of the batteries I'd be looking at to supply that voltage would be heavier than the drone could lift.

I'm looking for a lightweight circuit design to use fewer/lighter batteries to produce both the 24V to drive the motor as well as provide a lower voltage power to the Arduino which has an input voltage limit of 21V.


Part numbers:

  • 15V stepper option - PG15S-D20-HHB9
  • 24V stepper option - PG25L-D24-HHC1
  • Arduino - ABX00027
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  • \$\begingroup\$ Have you read something of this? realpars.com/stepper-motors-advantages/…. \$\endgroup\$
    – Antonio51
    Jul 14, 2022 at 13:20
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    \$\begingroup\$ Can the Stepper motor be replaced by a "servo-motor"? \$\endgroup\$
    – Antonio51
    Jul 14, 2022 at 13:32
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    \$\begingroup\$ The question is a bit broad. Battery weight and voltage are not correlated, try to estimate the available and needed energy first. \$\endgroup\$
    – Jens
    Jul 14, 2022 at 14:24
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    \$\begingroup\$ Radio controlled models use powerful but lightweight brushless motors, not stepper motors. Many use 8.4V max (2 lithium cells), 12.6V max (3 lithium cells) or 16.8V max (4 lithium cells). The lithium batteries are made in many sizes and are lightweight. If you stepup the voltage of a battery then its current is increased the same amount then its discharge time is very short. \$\endgroup\$
    – Audioguru
    Jul 14, 2022 at 14:51
  • \$\begingroup\$ @Antonio51 It needs to be a stepper motor since holding torque is necessary since it will be winding and holding a constant force spring, I need it to be able to do continuous 360 rotation, and I need some form of positional accuracy. So servos & DC are out and steppers are what I need. \$\endgroup\$
    – Lacey
    Jul 15, 2022 at 7:41

1 Answer 1

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I will bring together some thoughts here:

  1. The mentioned payload of the system is 400g. If you take the motor PG25L-D24-HHC1, there are 57g. Using two LiPo 18650 3Ah cells with protection there are +100g. Arduino Nano is +7g, a boost converter +15g maximum, stepper motor driver module again about +15g. Add some wires and you are at about 200g for a raw working system. The remaining 200g can be filled with additional cells in parallel, a housing and other mechanical components needed.
  2. The 2 LiPo cells provide a usable voltage range from 7.2-8.4V, for a run time estimation I take 7.8V. If I give the motor 200 mA continous current at 24 V and assume 90% efficiency for the boost converter, this will draw around 684 mA from the battery. Add 20 mA for the Arduino and 10 mA for the stepper driver module and the total current consumption will be 714 mA. This would run for a bit more than 4 hours using the 3Ah cells.
  3. Adding a second DC/DC converter from battery voltage down to 5V for the Arduino improves the battery efficiency slightly but adds weight, I don't think its worth the effort. So feed the Arduino directly from the battery using Vin.
  4. Do not use a stepper driver with bipolar output stages as mentioned in the motor datasheet, the efficiency is too bad. There are a lot of driver chips with internal current control PWM and step/dir interface, often seen in 3D printers.

There are many assumptions here, it is possible to allow up to 500 mA for the motor having less than 2 hours run time. The 200 mA guess was derived from the less powerful capabilities of the other motor. I just don't know what torque you may need in this application.

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