Session 29: Stepper stations and motor challenges
Learning outcomes
- Move a 28BYJ-48 a set number of steps with the Stepper library
- Measure the coil sequence on the oscilloscope
- Explain why a stepper can lose position
- Follow station rules for shared equipment
Kit and components
- Two stepper stations: Uno, 28BYJ-48, ULN2003 board, separate 5 V supply
- Oscilloscopes
- H-bridge circuits from S28 for students not at a station
Pre-reading about 20 min
Students read these on their phones before class. They are listed on the student Before class page.
Session plan
- 0:0010 minRecap
Quiz: H-bridges
- 0:1015 minDemo
The Stepper library and station rules
Run the worked sketch at one station on the projector. Show the IN1, IN3, IN2, IN4 pin order and read the station rules together.
- 0:2580 minStations
Stepper rotation and motor challenges
Pairs rotate through the two stepper stations in 20-minute slots: run the worked sketch, measure the coil frequency at 10 rpm, then move exactly one revolution. Everyone else works on the H-bridge exercises and a button-controlled motor challenge.
- 1:4515 minWrap-up
Open-loop control
Why the stepper cannot know it missed a step, and what a limit switch adds.
Checkpoint: ready to move on?
Every pair that visited a station has a measured coil frequency and a one-revolution move recorded in the logbook.
Extension for fast finishers
Non-blocking stepping with a button to reverse (lesson challenge).
Catch-up path
Students who miss a slot predict the coil frequencies from the lesson's table and take the first slot in S30.
Homework and practice
Final project proposal due in S30: problem, user, success criteria, block diagram and parts list.
Facilitator notes
- With two stations and 20-minute slots, eight pairs get a turn. Keep a rota on the board.
- Flex session: in a shorter course, demonstrate the stepper on the projector for 15 minutes in S28 instead.