When I disassembled the front panel of Nikola and inspected the connectors, I realized that we have to replace the old wiring/connectors with a new with an adjustable control system. There are many actuators to control, I decided to include all in the system except the heating and air conditioning of the cabin. I checked the fuel and temperature gauges and works perfectly, on a voltage of 6V the pointer shows full. I intend to use the temperature gauge for measuring the motor temperature, the fuel gauge will be for the battery pack voltage (the SOC will be displayed graphically in the Nextion display placed in between the speed gauge and analog clock).
For that task I choose Arduino Mega in combination with Nextion touch display. The actuators will be driven with a 16-channel relay module, each relay isolated by an optocoupler. The Nextion display is quite easy to program: a fine editor WYSIWYG makes programing very attractive hence the connection between Arduino is much more demanding. You can find our solutions in the GitHub link right above in the top menu of our site.
We put and wire the Arduino Nano, Nextion display, a fuse, 16-channel relay module and all connectors inside a solid box, so the tester is now portable and can be used in many other situations, where it is needed. In the Arduino code program you can see which pins were used for I/O, transmitting data to Nextion (Tx, Rx) and also Ardunio Nano (wire.h), the independent SOC meter device.