Stepper 28byj48 unipolar OK with uln2003
Slit the red wire so there are only two windings
Measured ohms across coils. Pin 1 ic - 5v pos ... (OMG, 16 connection
I did the same thing a long while ago. I vaguely remember I performed the following operation converting the stepper from unipolar to bipolar.
Open the casing
Cut away the red wire, so that the two windings do not electrically connected to each other.
Now I am googling something to read, and jot down some pictures, ...
Now the schematic for L293D driving a bipolar stepping motor.
I have found a L293D module in my junk box.
Now I have shrinked and merged 4 big pictures into one big picture for my small eyes to look at.
The problem is we don't know the colour code of the wiring scheme. For example, what colour is for 1a, 1b, 2a, 3b etc. If we could not find the colour code, we may need to use the multimeter and a 6 battery to find by trial and error manually.
Anyway, now I have removed the casing of the 5 wire unipolar motor. Next step is find out which trace to cut to separate the two coils sticking together at the red wire, to make it a 4 wire, two non connecting coils, red wire don't care bipolar motor.
Now I am also thinking of testing my old stepper and compare how more powerful is, comparing to the small guy. The old guy costed me US$2 (a couple of years ago). The wires were badly torn, but I know there is no contact brushes to wear, so found it good and quite. A new one costed US$25. I thought it was very good money for a hobbyist to play with and learn something. As a newbie, I needed to google hard before I know how to use a battery, a multimeter, and a 1 pole, 12 throw to figure out which wire goes with which other wire, ...
A stronger stepping motor to replace 28BYJ48, should be strong enough to turn Rubik cube
/ to continue, ...
(1) 28BYJ-48 - 5V Stepper Motor
(2) Stepping Motor Fundamentals - Microchip
(3) Control of Stepping Motors A Tutorial - DW Jones Uni Iowa, 1995
(4) L293x Quadruple Half-H Drivers Datasheet - TI
(5) MINI L293D DC/stepping motor controller board - ¥9.50
(6) L293D DC motor control card dual h-bridge Module - US$ 1.43
(7) Stepping Motor Tutorial (Unipolar/Bipolar, Half Step/ Full Step, ULN2003/L293D)
(8) Stepping Motor Tutorial Using L298N Driver
(9) How does a Stepper Motor work? (Youtube 6 minute video) - Learn Engineering 3.17M subscribers 2,453,537 views 2016oct19
Appendix A - Why we need a dual bridge motor driver (L293D or L298N)?
We need to use two H-bridge circuits (dual H-bridge) to drive both
coils of a bipolar stepper motor.
How does a H-bridge circuit work?
The field effect transistors (FET) Q1 to Q4 act like switches. The
diodes D1 to D4 act like freewheeling diodes to channel
back-electromagnetic force (back-EMF) of the motor coils. When the
‘switches’ Q1 and Q4 are closed (and Q2 and Q3 are open) a conducting
path is created and current will flow from +9Vdc to Q1 to the coil to
Q4 to GND. By opening Q1 and Q4 switches and closing Q2 and Q3
switches, a different conducting path is generated from +9Vdc to Q2 to
the coil to Q3 to GND. If you pay close attention you will notice the
current flowing through the coil in the opposite direction, allowing
reverse operation of the motor.
Note however the switches Q1 and Q2 should never be closed at the same
time, as this would cause a short circuit. The same applies to the
switches Q3 and Q4. This is why we cannot simply use Arduino [or Rpi] HIGH and
LOW outputs to reverse the polarity; a H-bridge circuit is essential.