Support » Pololu Simple Motor Controller User’s Guide » 3. Getting Started »
3.5. LED Feedback
The Simple Motor Controllers have three indicator LEDs that provide feedback about the current state of the controller. The LEDs can tell you whether an error is occurring, whether the USB connection is active, what direction the motor is driving, and much more.
Simple Motor Controller 18v7 LEDs.
Simple High-Power Motor Controller 18v15 or 24v12 LEDs.
Simple High-Power Motor Controller 18v25 or 24v23 LEDs.
The Simple Motor Controllers have three indicator LEDs:
Green USB LED
This LED indicates the USB status of the device. When the Simple Motor Controller is not connected to a computer via the USB cable, the green LED will always be off. When you connect the controller to USB, the green LED starts blinking slowly. The blinking continues until the controller receives a particular message from the computer indicating that the Simple Motor Controller’s USB drivers are installed correctly (see Section 3.1 for driver installation instructions). After the controller gets this message, the green LED turns solidly on, except for brief flickers whenever there is USB activity. The Simple Motor Control Center software constantly streams data from the controller, so when the control center is running and connected to the Simple Motor Controller, the green LED will flicker constantly.
Red Error LED
This LED turns on whenever there is an error stopping the motor (see Section 3.4 for information on errors that can stop the motor). The red LED is tied directly to the active-high output ERR, which allows the error status to be monitored by an external device such as a microcontroller. When no errors are stopping the motor, the error LED is off and the ERR pin is pulled low. See Section 4.2 for more information about the ERR pin and the error LED.
Yellow Status LED
This LED helps you visually identify the state of the device, which can be useful when the controller is not connected to the Control Center. On start-up, the status LED briefly flashes a pattern indicating the source of the last reset (see the Reset Flags variable in Section 6.4 for more information):
- 8 blinks over the first two seconds after start-up indicates that the external RST pin was driven low to reset the controller.
- 3 blinks over the first two seconds after start-up indicates that the controller last reset because logic power got too low (power was disconnected or the controller browned out).
- Rapid flickering for the first two seconds after start-up indicates that the controller was reset by a software fault or by a firmware upgrade.
This startup behavior can help you detect if your Simple Motor Controller is browning out and resetting unexpectedly (as can happen if your input voltage drops due to high power demands or electrical noise).
After the start-up phase ends, the status LED primarily gives feedback about the motor driver outputs:
- An even blinking pattern of on for 2/3 s and off for 2/3 s indicates that the controller is not driving the motor and has not yet detected the baud rate. This pattern only occurs when the controller is in USB/serial mode with automatic baud detection enabled and helps you determine when you have established communication between a TTL serial source and the Simple Motor Controller.
- A brief flash once per second indicates that the controller is not driving the motor. If the controller is in Serial/USB mode with automatic baud detection enabled, this pattern additionally indicates that the Simple Motor Controller has successfully learned the TTL serial baud rate.
- A repeating, gradual increase in brightness every second indicates that the controller is driving the motor forward.
- A repeating, gradual decrease in brightness every second indicates that the controller is driving the motor in reverse.