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Intro

I have developed a 2-wire control bus for e-bikes. The signal and the power supply go together with in total two wires: GND and 5V. With this bus we can wire among other the throttle switch, brake sensor, pedal assist sensor and the speed sensor. Because the number of cables has been reduced drastically, very robust RC-model connectors can be used, because these connectors are only available with a maximum of three pins.

Each sensor only needs 1 resistor to work. In addition, the sensor can also be powered by the 5V.

Robust RC-model connectors used for an ebike
Robust RC-model connectors used for an ebike

Two-wire LIN bus

There is a standardized 2-wire control bus: LIN (Local Interconnect Network). This is a serial network protocol used for communication between components in vehicles. But with LIN, each sensor requires its own microcontroller board, which reduces reliability and also takes up too much space. My 2-wire current controlled bus is a simple alternative to this. Each sensor only needs 1 resistor.

Only one resistor is required per sensor

For example, see the the throttle with one resistor per switch:

Throttle switch wiring with the simple 2-wire bus
Throttle switch wiring with the simple 2-wire bus

Cable killer two-wire control board

One microcontroller board is required to control the two-wire bus. I've called it the "cable killer" board. It has several functions:

  • It is small enough to build into the motor controller.
  • It gets rid of the rat's nest of cables coming out of the motor controller.
  • It can communicate to an LCD display or smartphone wirelessly.
  • It supports all kind of bicycle electronics, such as torque sensor, temperature sensor, shift servo etc.

Robustness against leakage currents and current variations

The electronic has proven to be very stable, even when currents drifts occur. But if an error may occur, the system switches off and an error message is displayed by a LED.

Cable killer PCB

Simple 2-wire control bus for ebikes
Simple 2-wire control bus for ebikes

Simple 2-wire control bus for ebikes
Simple 2-wire control bus for ebikes

Ebike wire reduction

Here is a view of the rat's nest of cables coming out of a motor controller:

Rat's nest of cables coming out of a motor controller
Rat's nest of cables coming out of a motor controller

Here's the new reduced cabling with the two-wire current controlled bus:

E bike cabling reduction with 2-wire current controlled bus
E bike cabling reduction with 2-wire current controlled bus

2-wire current controlled bus “Cucobus"

I have called the current controlled bus with “Cucobus”. It is a bus with the least number of wires possible, only two: GND and 5V.

Maximal 7 switches can be connected to the Cucobus. When a switch is pressed, the 5V is loaded with a resistor, see the circuit. The cable killer measures the current from the 5V and deduce from this which switches have been pressed. For safety reasons, no errors are allowed here. As a result, the development of the cucobus took a lot of time and is quite complicated. For example, compensation is made for the supply current of the Hall sensors. The bus is continuously calibrated and if a suspicious fault occurs, the system is shut down.

Two current controlled busses are needed, one for the electronics at the bicycle frame and one for the handle bar. Just a single 3 pole connector is needed for the control of an ebike:

Robust two-wire (GND, 5V) current controlled bus for ebikes
Robust two-wire (GND, 5V) current controlled bus for ebikes


The E-bike cable killer works for all types of motor controllers and is small enough to fit into the small KU63. It consists of two PCB’s, the main PCB is built into the motor controller, the front PCB replaces the front plate thereof.

E bike cable killer inside KU63
E bike cable killer inside KU63

E bike cable killer inside KU63
E bike cable killer inside KU63

Circuit description

This is the old circuit version v0, used in the Maxun One solar bike for many years now:

E bike cable killer circuit v0
E bike cable killer circuit v0

Here's the newer circuit v1 that is not finished yet:

E bike cabling reduction with 2-wire current controlled bus
E bike cabling reduction with 2-wire current controlled bus

Future development

The E-bike cable killer is very robust, I've used it at my solar bike for more then 10,000km without any errors. Still, a new improved version has to be made. But since I'm working on an important invention, I don't have time to required finish this project. I would like someone else to take over this project, I will help with that.

These are the main improvements:

  • The 5V switching power supply is now synchronous
  • The SAMD51 is replaced by an STM32 controller

Fora

Control of additional components

The cable killer has two also two extra connectors, JM4 and JM5, for the control of components such as lights, torque sensor, temperature sensor, shift servo etc:

E bike cabling reduction with 2-wire current controlled bus
E bike cabling reduction with 2-wire current controlled bus

2-wire control bus development

Here are photos that give an insight into how the Cucobus works:

Current controlled bus development
Current controlled bus development

Current controlled bus development
Current controlled bus development

Do you have any comments about the website? Please let me know.