Instrumentation

A big part of Electric Vehicles is the instrumentation that is possible with a electric motor.  There are some generic systems that can monitor basic functionality of the system and display it on a small LCD, but as with most of the elements of Jane, this too is going to be have to custom built.

The good news is there are now off-shelf electronics available that can be utilized.

Available information

The Kelly KHB72701 controller has an optional CAN bus.  This provides an industry standard bus that allows a computer to communicate with the controller.  The controller has a wide range of data available via the CAN bus.

Available Data includes

1) Voltages: Batteries, controller supply, accelerator sensor

2) Motor Specs: RPM, Motor current and Phase Width Modulator (PWM) value

3) Temperatures: Controller and Motor

4) Switch Settings: Reverse & accelerator micro-switch

Notes: The CAN BUS is internally terminated within the Kelly Controller.

All that is needed is small computer than can read and display this.

Arduino

The Arduino platform is a great development system.  There are a number of controllers available along with accessory boards that mount directly on the controller, allowing for easy to configure HW solution.  Also, many libraries exist to help jump start development.

Useful links:  

Main Arduino Page  - We are using an Arduino Uno

CAN Bus Adapter Board (called a shield)

LCD Shield

These three boards mount together and will the main controller for Jane.

Software

Here are the project specific files for the Sketch that generates the dashboard below.  Google Drive Link

I'll have to dust off my software skills to start work on the C code for the Arduino board.  Luckily it won't take much to have it perform basic dashboard functions.  The key data I would like to display realtime is:

Motor RPM --> which can be used to calculate vehicle speed if the gear is known.

Motor and Controller Temperatures --> Need to make sure nothing is getting too hot

Motor Amps as reported by the controller

Battery Amps as measured by a current shunt

Drive/Reverse - To confirm the electronic Reverse is working

Controller Errors --> Just in case something goes wrong

Here is a picture of the prototype display 

Battery Current Measurement

The real measure of power and efficiency requires accurate battery voltage and current measurements.  The controller does not report battery current so a current is installed on the ground side of the power going to the controller.  Using the negative side helps eliminate common mode voltage since the motor battery is not connect to the 12V battery which powers the controller.  The shunt is a low resistance resistor that will generate 75mV from a current of 600A.

The current plan is to install a Amp-Hour (AH)  & Current meter like this meter from Elite 600A-90V Digital Dual Display.  It will provide instantaneous readings plus it offers some alarm capability.