Advice on first design - Page 1
Forum section: electronics / beginners

author: jnicolson
author_rank: Newbie
timestamp: July 26, 2020, 07:16:36 am
content: Hi All! Long time lurker, first time poster here! Another request for advice - this is the first PCB i've designed which I intend to get fabricated and then build. It's a 2 layer board which I hope to get made at one of the cheap Chinese manufacturers.The purpose of this is to act as a controller for a Tesla Wall Charger. These can work in a Primary -> Secondary arrangement to share a circuit, but some clever people (including people who posted on this forum) reverse engineered the protocol with the goal of controlling based on external inputs (such as solar generation).The existing project is based around a Python program running on a computer like a Rapberry Pi Zero W. In order to reduce the power consumption and let me centrally control everything, the purpose of this is to have an ESP32 (top centre) which will read from an external source (such as MQTT) - basically moving the logic and having the controller be much lighter weight.The Primary -> Secondary control is via RS485 (controller top right). I include a CANBus transceiver (top left) in case anyone decodes the CAN Communication with the car over the signal wires. I probably won't populate this on my first go though. Power is via the ribbon cable which feeds the front panel LED - ~14V.Design wise it's designed to plug directly into the ribbon cable connector on the LED front panel board, then the ribbon cable plugs into this one. Everything is passed straight through except VCC and GND. VCC goes to a buck regulator (bottom center). There is also a I2C temperature sensor (middle right) on there for fun as well as a few GPIOs broken out in case something comes to mind later.Greatly appreciate any input! Images have the flood fill turned off - both top and bottom are flooded with ground and full project files (KiCAD latest daily release) are available in a github repository:https://github.com/jnicolson/TWCController

author: tggzzz
author_rank: Super Contributor
timestamp: July 26, 2020, 08:14:08 am
content: I haven't looked at your design, but I can offer these general observations...Don't just consider how it works, consider how it fails and the consequences of failure.I suspect high energies and voltages are in the system. What happens if they "escape", whatever that might mean?In general, failures to consider include individual electronic components (e.g. open/short/indeterminate), signal integrity in the presence of interference, software, network, and especially anything "in the cloud". Never forget the eight fallacies of distributed computing

author: mariush
author_rank: Super Contributor
timestamp: July 26, 2020, 09:27:12 am
content: Seems like you could really optimize those traces by rotating U4 90 degrees clockwise. No idea how that would affect the antenna part though... i guess depends on the box in which the board will sit.

author: Unixon
author_rank: Frequent Contributor
timestamp: July 26, 2020, 03:37:02 pm
content: R8 is 36.1Ohm, this looks weird... is there a typo in schematic? 36.1kOhm is also wrong, this results in 3.7V output, not 3.3V.For 3.3V and TPS56339 this must be 36k over 11.5k.