u/RohitRojo

I'm designing my own RC Car as a learning project over the summer. I hope to learn more about PCB design, electronics, and power through the process. I've designed some PCBs before and did some PCB projects for classes and my design team. This was a relatively simple board for me to design since there are very few components.

After my previous PCB failed in ways that I'm unable to comprehend, I decided to split the system into multiple parts and connect them with wires, hopefully making the debugging process simpler. Plus, if a single part/board fails, it'll be easier to replace that part rather than the whole system. At the end, I (might) design a singular PCB for the whole system.

This Motor Driver Dev board uses the MP6551 motor driver to drive two spare motors I have. I believe my motors are the PAN14 motors. The MP6551 outputs 5A, which should work well since the motors are rated for 4.8A and I expect a small amount of power loss. I will use the Molex Mini-fit connectors and the respective headers to power the board and transfer power from the board to the motors. I used the recommended PCB layout in the datasheet of the motor driver to guide the layout of my board.

The motor driver will be controlled using an Arduino Nano (RP2040 Connect) or an ESP32 C3 (official Dev Module) through header pins and DuPont wires. The header pins also have current measurement pins as outputs to be read by the MCU.

The board and motors will be powered by a 2s Li-ion battery (7.2V nominal). I used 8.4V for current/resistance calculations for the LEDs.

The board also has two mounting holes for M6 screws on one side, and testpoints for each motor output. They're not labelled on the board.

The board is about 2 x 1 inches, so it's relatively small. I'm not opposed to making it larger if necessary.

Since I have a bit of experience but lots to learn, I am open to all levels of feedback. I do not plan to pursue a career in PCB design, but I want to master PCB design so that I can guide my peers better.

https://preview.redd.it/35hhuug43k9h1.png?width=3836&format=png&auto=webp&s=554977e98ac360aa843cf3e119b5326564380ae6

https://preview.redd.it/r3ry0vg43k9h1.png?width=3840&format=png&auto=webp&s=9f214c59787207cbe70c50064071cd40041aeff5

https://preview.redd.it/bdkqrvg43k9h1.png?width=3836&format=png&auto=webp&s=a59272abb69646718d69355a8ea2009e1987e590

https://preview.redd.it/rviilug43k9h1.png?width=1892&format=png&auto=webp&s=036590d3fbac3e60a03c47d4eb4af2932ddfc436

Thanks for taking a look!

Note: The reference designators don't all start at one since there's another schematic+PCB in this project

I'm using a VNH5200 motor driver for my RC Car. The datasheet provides a typical application circuit shown below. Underneath, it includes a note about a large blocking capacitor.

The circuit shows three symbols I don't understand. The one circled in red seems like it would be the large blocking capacitor, but why are there multiple connections to it? The capacitor circled in blue is a capacitor too, but that might just be a bypass capacitor. Can someone also confirm that the capacitor circled in blue should be connected to ground? Lastly, what is the component circled in green?

Edit: muC circled in red is the MCU

Edit 2: I'm confused by the purpose of the pull up resistors for the DIAG/EN pins -- are they not supposed to be controlled by the MCU? Are they connected to the MCU only for detecting a fault?

Also, 500uF is very large. Would an electrolytic capacitor suffice?

https://preview.redd.it/jpkhnj03wx8h1.png?width=1656&format=png&auto=webp&s=5cd7cec1c155326647bdfa22cba6e3b196e0ac98

I was reported for not picking up a delivery. I couldn’t figure out which delivery I was reported for, but I have a suspicion that I was reported for a courier service delivery (they took too long to figure out payment, they wouldn’t give me the package until they were paid, and I had another order in the car; i ended up cancelling after waiting 10+ minutes). Do I need to be worried about this singular report? Will it affect my future orders/payments?

I'm designing an RC Car with an Arduino Nano, DRV8421 motor controller, and some spare parts from an RC helicopter (motors and 8.4V battery pack). When the Arduino drives the motor controller, the motor just produces a whining noise and doesn't spin. I removed the motors to measure the voltage and current. Without the motor attached, I'm getting 8.3V and 2A from the output of the motor driver. When I connect the motor, the current drops to 2mA. Why does this happen? I've tested these motors with an L293D, and they were able to run fine. I designed my PCB for the DRV8421 since it conducts higher currents.

Here's the Altium design. Note that my printed+assembled PCB looks slightly different since I updated the design -- The motor OUT connections don't have vias on and the traces are 15mils instead of 20mils on fabricated.

I ordered some JST 02HR-6S-P-N connectors from DigiKey. I thought it would be convenient that I can order the crimp connector and receptacle at once. However, I can't figure out how to crimp it since the crimp connector is already in the receptacle. Am I supposed to be able to pluck the crimp connector out with tweezers, crimp the wire, and then put it back in?