Safety Control Unit
The past weeks at Nova Electric Racing I’ve been working on a design for the Safety Control Unit. This unit is responsible for shutting down the motorcycle when unsafe operation is detected. This can happen for example when the battery pack gets too hot. Since this system is there for safety reasons it is critical that the design of the unit works as expected. Furthermore it is nice to be able to test this before building your first prototype board since this can save a lot of extra time and money. To do this I was able to use a tool called LTSpice which we learned about during my minor in Electrical Engineering for Autonomous Exploration Robots. LTSpice allows you to build a circuit using various components (either using ideal components or even actual models from manufacturers). Afterwards LTSpice allows you to simulate the behaviour of your design, enabling you to check which voltages occur at certain nodes and how currents are flowing through the circuit.
The picture below shows a simulation of the safety control unit. In green are the start signals (generated when the user tries starting the bike) and in red the shutdown signals (generated when unsafe operation is detected or when manually shutting down the bike). In dark blue is a signal that has to be switched immediately based on these inputs and in light blue a signal that has to be switched after a small time delay based on this signal. This graph shows me that the board indeed works as expected during simulations.
Having verified that this design works in a simulation I can now, with more confidence, move on to designing and building the first prototype board which I can use to verify that what I tested in simulations also has the expected behaviour when build on a PCB.