EMC Consutancy & Design solutions
OBD2 IoT
Garages are now able to check the state of a car's engine within a matter of seconds by using the OBD2 standards. In spite of this, what most people are not aware of is the fact that the OBD2 connector that we all see in most cars comes with protocols that are undocumented and that they are specific to the manufacturer of the car. I find this to be both fascinating and very scary at the same time. In order not to bore you with too much detail, I would like to give you a very brief overview of the main issues encountered on this particular project.
don't add too many vias in the same place
There are a few mistakes in this design, and I will point out two of them.
It was found that there were too many vias below the microcontroller, and the anti-pad vias were also too large, and that was the first error. As a result of this, the return current between the vias will be broken. As an attempt to describe this in a more detailed manner, I have created the drawing on the left which shows what the "loop" created looks like. As you can see from the drawing. The issue with this OBD2 scanner was quite severe. In fact, there are quite a few emissions above 300 MHz as a result of issues such as this all over the PCB.
We have redesigned the PCB layout keeping an eye on the return current of each trace and the issue has disappeared after our layout.
Surge test on the CAN BUS
There may be some people who think that the 12V battery car cannot have surge in it since the 12V comes from a battery, but that's not true. As far as I am concerned, there is nothing more incorrect than this assumption. During the start-up process of most modern EV cars, there is a possibility of voltage surges up to 500 V. Therefore it is necessary to have surge protection on the OBD2 12 V connector. There are several types of overvoltage protection on the market but all have different characteristics. For the purpose of this particular application, I will not mention which one was used. Nevertheless, after our design was completed, the OBD2 tester was tested and, this time, it passed EMC testing as well.