BBB Beetleweight Single Brushed ESC v4

Example Robot: Abracagrabra by Rebecca Wilton

Rebecca built this magical lifter robot Abracagrabra – she runs two BBB Single Brushed ESCs – one per side each powering two BBB 22mm motors, see the wiring diagram below for how to add four motor drive to your robot.

More info about the ESC:

Please note: these are single ESCs and you will need one per drive side of your robot. You’ll need to set up mixing on your transmitter – Mixing Guide.

LED indicator light & beeps:
Start up beep = ESC has just powered on – it is receiving power and is connected to motor(s).
Solid LED = Powered on. Receiver ready, ESC is armed.
Flash & beep with short gap = Powered on. Throttle isn’t centred.
Flash & beep with long gap = Powered on. No receiver signal.

Programming:
These ESCs can be configured with a BBB ESC programmer or an arduino. You can configure the current and temperature limit, enable the limit switches and more! More info  & video tutorial on the programmer page.

Wiring diagram for two or four wheel drive:

Note: You do not need to cut the red servo wire on one of the ESCs for v4s!
Components in this example: 3S or 4S Lipo, Beetle Safety Kit, Breakout cable, BBB ESCs, BBB 22mm Motors, BEC and Flysky Reciever.

Microswitch End Stops:

Useful for brushed weapons that don’t continuously rotate such as axes and lifters, you can attach a microswitch at each end of the range (as an end stop like a 3D printer or CNC) to help prevent stalling out of motors and damaging your gears  – diagram for v3 below. End stop mode is off by default on the ESC and needs to be enabled with a programmer or we can ship it enabled – let us know in the order notes.
Note: on v4 ESCs : FWD = F, REV = R, COM = C

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.