This is my attempt at making a variable speed motor controller for 4 Lego Technic PF Motors using the following parts.
1x Arduino Mini Pro
2x Chinese L298N PWM 1.5A Dual Channel Motor Driver modules
1x HC-05 Bluetooth Serial module
The boards have in1, in2 for each channel that can be set as below
| in1 | in2 | Motor Behavior |
|---|---|---|
| lo | lo | Standby |
| hi | hi | Brake |
| lo | hi/PWM | Forward |
| hi/PWM | lo | Backward |
Since I would need 2 PWM pins per channel for this config for a total of 8pins which Arduino mini doesn't have.
I'll use the config below
| in1 | in2 | Motor Behavior |
|---|---|---|
| lo | lo | Standby |
| lo | PWM | Forward |
| hi | ~PWM | Backward |
~PWM: Use 255-pwm value to turn the motor on in the OFF part of the PWM cycle.
The Arduino is controlled using a simple mobile app created with the [MIT App Inventor] (http://ai2.appinventor.mit.edu).
It uses the following char based command protocol with each command terminated with a newline.
command format: P "1byte port num" "1byte OP code" "arg"\n
| Commands | Description |
|---|---|
| P0E1\n | Enable Port0 |
| P0E0\n | Disable Port0 |
| P0S100\n | Port0 Fwd Speed 100 |
| P1S-200\n | Port1 Rev Speed 200 |
Wiring the output to 4 Lego PF connectors, the pinout is as below.
The output of the L298N will go to C1 and C2. The GND and +9v is required for the Servo, the M, L, XL motors don't need them.
