Fab Academy 2025

@ Fab Lab Rwanda, Kigali

Output Devices

Output Devices


  • Team Kigali
  • Team Botswana
  • Week 10 - Output Devices

    Group Assignment

    This week we had to measure the power consumption of an output device.
    We decided to test a stepper motor since we had one available in our lab and wanted to understand how much power it actually uses.

    Our testing setup with the stepper motor Power measurement with multimeter

    What we did

    So basically we took this stepper motor (model 17HS4401S) that we found in the lab and tested how much electricity it uses under different conditions. It was pretty interesting to see the differences!

    Quick explanation of terms (for those who don't know)

    What it is What it means
    Power Supply The thing that gives electricity to other stuff. Ours can be adjusted to give different amounts of voltage
    Voltage (V) Think of it like water pressure - higher voltage = more "push" for the electricity
    Current (A) How much electricity is actually flowing (like how much water is coming out of a hose)
    Multimeter Tool for measuring electrical stuff - voltage, current, resistance, etc.

    The Motor We Used

    We picked the 17HS4401S NEMA 17 stepper motor. These are pretty common in 3D printers and CNC machines, so it seemed like a good choice for testing.

    The stepper motor we tested
    17HS4401S NEMA 17 Stepper Motor
    Motor specs on the label
    Specs printed on the motor

    What the motor specs say:

    Power Supply Setup

    We used this adjustable DC power supply that we have in the lab. It's pretty nice because you can control both voltage and current, plus it shows you what's happening in real time on the display.

    Front of the power supply
    Power supply with all the knobs and displays
    Digital readout
    The screen showing voltage and current

    The display shows both voltage and current at the same time. There are two sets of controls - "coarse" (moves fast) and "fine" (for precise adjustments). We looked at the motor label to figure out we needed 12V.

    One thing our instructor told us - always set current limits! If you don't, LEDs can get hot and pull more current until they burn out. Same goes for other components.

    How we set it up:

    1. First, set voltage to 12V using the coarse and fine knobs
    2. Turn everything off and short the test leads together
    3. Turn back on and set current limit to about 1.5A (bit under the motor's rating)
    4. Connect the motor and see what happens

    Using the Multimeter

    We also used a multimeter to double-check our measurements. The power supply can measure and supply at the same time, but the multimeter only measures (which sometimes makes it more accurate).

    Measuring current with multimeter
    Multimeter in series to measure current
    Measuring voltage
    Multimeter across the motor for voltage

    Our Test Results

    Test 1: Motor just sitting there (not moving)

    Motor powered but stationary
    Motor getting power but not turning
    Power reading during idle
    What the power supply showed

    What we measured: 12.0V, 0.85A, so that's about 10.2W

    Test 2: Motor spinning freely

    Motor spinning
    Motor rotating with no load on it

    What we measured: 12.0V, 0.92A, so about 11.0W

    Test 3: Making it work harder

    Then we tried holding the motor shaft while it was trying to turn, making it work harder. As expected, it needed more power to fight against our resistance.

    Applying load to motor
    Holding the shaft to create resistance
    Higher power consumption
    Power consumption went up significantly

    What we measured: 12.0V, 1.42A, so about 17.0W

    Summary of our measurements

    What the motor was doing Voltage Current Power
    Just sitting there (holding position) 12.0V 0.85A 10.2W
    Spinning freely 12.0V 0.92A 11.0W
    Working against resistance 12.0V 1.42A 17.0W

    What we learned

    Some interesting things we noticed:

    Overall this was a pretty useful exercise. We didn't expect the motor to use so much power just sitting there, but now we understand why stepper motor drivers often have features to reduce holding current when the motor doesn't need to move.

    Instructor

    Contacts

    • Map
    • +250 781 187 555