Kyung Yun Choi

Build a Bipolar Stepper Motor Driver Board!

Week 9: Output Devices

This week we learned about different types of output devices and fabricated PCB for controling the output device. For my final project, I decided to control the stepper motor for this week assignment.

Stepper Motor

I bought a bipolar stepper motor for my final project. It will be used for actuating the bubble iris attached with a string. NEMA 17- Body length: 34mm

The principle of a bipolar stepper motor is well explained on the below animation (referenced from link)

why not servo motor instead of stepper ?

Circuit

I used the same circuit design of fab class as shown on the below image. The circuit uses two motor driver IC chip (A4953)

First I fabricated the board using the mods but since I didn't check the firm adhesion of the copper board on the sacrificial layer of the milling machine, the trace had weird shape looks like drawn by hand. Also, when I tried to milling the outline of the board, the double-sided tape started to being detached from the sacrificial layer and I wasn't able to complete the board cut clean.

So, I had to cut out the board manually using the wire cutter and some part of board's edge was teared apart and damaged the trace

To connect the damaged traces, I just soldered a wire between the damaged traces which was the vcc line for the driver board. But when I tried to upload a code through the ArduinoISP, my laptop was not able to detect the ATtiny 44 chip on the board and the chip got very hot that even I couldn't touch it. But I couldn't find any shorted line on the board with multimeter and just assumed that the chip might be damaged. So I replaced only the chip but it still didn't work.

So I made another same board and this time I was able to fabricate the board unimpaired. Now I have two boards which are I call old and new.

Debugging

The problems I found during uploading the code through the ArduinoISP.
  • Getting the ATtiny44 very hot is happen when I disconnect the power to the board but keep the ISP vcc connected.
  • After connecting the power and ISP, I was able to upload the code on the motor driver board but the stepper motor didn't move at all
  • That was because I used the 5V output from the Arduino UNO to power the board and it was not enough to drive the NEMA 17 stepper motor
  • I supplied 12V to the power jack of the board and the motor started to move
  • As shown on the above, the old board drained more current upto 0.7A while the new one took 0.5A
  • Even though the old one was working, the motor speed was significantly different. 60 rpm but the old one looks like 20 rpm.
  • Test