EV Fundamentals: CANBus Cable Introduction
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CANBus Cable Introduction
04.48
| 00:00 | CAN bus is a communication protocol that's commonly used in modern automotive applications due to its robustness and fairly cheap implementation. |
| 00:07 | It allows controllers and devices to communicate with each other efficiently, sending hundreds or thousands of different commands and sensor signals over a two-wire network without having to individually wire each component. |
| 00:18 | This is a massive savings of weight and complexity compared to running analog wires for every individual signal. |
| 00:25 | CAN stands for controller area network and this network runs through buses , which are simply two wires twisted together that connect all of the devices on the network. |
| 00:34 | Before we jump into this topic, I should point out that High Performance Academy does have a complete course that dives deep into CAN communication. |
| 00:41 | It's a big subject that definitely warrants its own course. |
| 00:44 | With that in mind, in this module we're just going to cover the important points to consider specifically in relation to CAN for EVs. |
| 00:51 | Essentially, the must-know points that may save a lot of headaches down the road. |
| 00:54 | But if you finish this module and find yourself wanting to learn more about CAN, I highly recommend you check out the full course, which you'll find a link to below. |
| 01:02 | Nearly everything is communicated via CAN on EVs and the vehicle control unit relies on that communication or the vehicle simply won't function. |
| 01:09 | In some ways, they're the two most important wires in the vehicle. |
| 01:13 | It's crucial that CAN is properly routed, terminated, and respected. |
| 01:16 | If the CAN bus has errors or goes down, the entire car will most likely be disabled. |
| 01:20 | So, this is why it's common to see multiple CAN buses in one vehicle. |
| 01:23 | If there are some components that are prone to risk, for example sensors that are mounted in the wheel wells, it's a smart idea to put those on a separate CAN bus in such an arrangement that if that bus is damaged, the entire vehicle's operation isn't impacted. |
| 01:36 | This way, systems remain independent from each other and a damaged or disconnected CAN bus that works with some relatively unimportant body or lighting functionality won't take down the entire powertrain. |
| 01:47 | With EVs, it's a very good idea to keep the high voltage system on its own CAN bus, isolated from other components. |
| 01:52 | This single bus would typically contain the inverter or inverters, the vehicle control unit, plus the BMS, DC-DC, and charger. |
| 02:01 | A separate bus would then be used for data analysis sensors and a third bus could be used for other vehicle functions. |
| 02:07 | CAN cables and other analog signal cables should always be routed away from high voltage lines when possible, specifically the motor to inverter cables as these cables create the most electromagnetic interference, commonly referred to as EMI, due to their high frequency high amplitude current. |
| 02:21 | However, the good news about CAN is that it uses differential signaling, which is designed to cancel out noise and interference. |
| 02:28 | This is why the CAN wires are twisted together. |
| 02:30 | If the interference affects each wire equally, in theory the noise should be canceled out. |
| 02:34 | The best practice for these twists is that they should occur every 50 millimeters or so and it's important that this rate remains consistent for the entire bus. |
| 02:42 | If cables do need to cross over high voltage lines for some reason, it's best to have them cross perpendicular to each other as that reduces the amount of area under influence of EMI. |
| 02:52 | So, throughout this network we have all the devices , which connect to the CAN bus. These are referred to as nodes. |
| 02:57 | A node is any device or component that's connected to the bus and can transmit or receive data. |
| 03:02 | The general rule of thumb here is that these nodes should be no more than 300 millimeters away from the bus, however in practice that's often not possible and generally lengths under one meter won't pose any issues. |
| 03:13 | The last key piece of knowledge I want to cover when it comes to the CAN bus is the terminating resistor. |
| 03:18 | This is a resistor that's placed at each end of the bus to prevent signal reflections and ensure proper signal integrity. |
| 03:24 | It's crucial in cutting out electrical noise and keeping the entire network stable and reliable. |
| 03:29 | Terminating resistors are typically placed inside connectors of components at either end of the bus. |
| 03:34 | Never put a resistor in the middle of a wiring loom where it could be damaged or hard to locate. |
| 03:39 | CAN might seem daunting, but it's a complete game changer for modern vehicles and much of what we enjoy now just wouldn't be possible without it. |
| 03:46 | In fact CAN has been around for a long time and as vehicles continue to get more and more complicated and advanced, newer and faster communication protocols such as FlexRay and Ethernet are now being used. |
| 03:56 | Once you get your head around the basics a whole world of possibilities opens up and as I mentioned earlier check out the CAN bus communications decoded course linked below if you're interested in learning everything there is to know about the subject. |
| 04:08 | Okay, time for a quick wrap-up of this module before we move on. |
| 04:11 | A commonly used communication protocol in the automotive space, CAN bus allows for communication between all of the components in your vehicle without having to wire each signal separately to each device that wanted access to that signal. |
| 04:23 | This means that many different components can be on the same bus relying on that bus to communicate with each other. |
| 04:28 | This can be problematic if that bus fails causing the entire shutdown of everything else. |
| 04:32 | It's for this reason that it's best to separate critical and non-critical functions into different buses. |
| 04:37 | CAN cables are susceptible to interference especially from high voltage components so always ensure using twisted pair cable with CAN and avoid crossing over hv cables whenever possible. |
