BBB Brushed ESC Programmer

Programming guide:

1. Connect the ESC servo wires to the programmer (ensure Sig to white, + to red, – to black)
2. Install & open Arduino software on your computer and look at the list of COM ports (Tools > Port)
3. Plug in the USB cable to your computer and select the new COM port in Arduino
4. Open the Serial Monitor in Arduino (Tools > Serial Monitor) and set the baud rate to 9600
5. Connect power to the ESC’s power wires (red and black wires)
6. Use the Serial Monitor to type commands – try “help” to start.

Overvolting guide:

All motors are limited by the amount of current they can draw, as electrical current generates heat and eventually burns out a motor. Combat robot motors are generally rated so that they will draw a suitable (non-firey) amount of current at the rated voltage in practice. Key background:

• A motor’s speed is proportional to the voltage used (more volts = more RPMs)
• A motor’s maximum current draw is proportional to the voltage used (more volts = more amps)
• A motor’s torque is proportional to the current draw (if the motor is heavily loaded / stalled, its producing more torque and drawing more amps)
• Heat buildup is proportional to the current draw (more amps = more heat)

Simply overvolting a motor yields more speed, current and torque but also more heat, meaning an increased risk of burning out the motor. By overvolting using an ESC with appropriate current limiting, we can still achieve higher RPMs, but keep the current draw and torque consistent, preventing any excess heat buildup. This on its own, would yield higher drive speeds. If we adjust the gear ratio to the wheels, we can boost speed and torque together!

Theoretical case study:

• A robot with BBB 22mm’s direct driven and a 4S lipo, can move at 10mph and generate torque to push a 2Kg weight.
• The same robot with 8S (and ESC’s limited to ~3.5A) can move at 20mph and generate the same torque to push a 2Kg weight.
• The same robot with an additional (e.g. 3D printed) set of gears (with a 1:1.5 ratio) can move at 15mph, and generate torque to push a 3Kg weight.
• The same robot with an additional (e.g. 3D printed) set of gears (with a 1:2 ratio) can move at the same 10mph, and generate torque to push a 4Kg weight.

Key takeaways:

• Overvolting should only be done with a current-limiting ESC set to an appropriate current limit (the limit will vary depending on your motors!) – current limiting may only be effective when driving 1 motor from 1 ESC.
• Overvolting in this fashion increases the maximum RPM of your motor, but not its torque output
• Additional gearing can be added to trade some/all of the extra RPM for extra torque.

Arduino Programmer Guide:

• Recommended to use an Arduino Nano.
• Solder a 1kOhm resistor between D3 & D4.
• Solder pins to GND, D2 & D3.
• Upload the Arduino sketch here.
• Then follow the programming guide above.
• Note: Plug in D3 to white, D2 to red, GND to black servo connectors on the ESC.