Welcome to a new video it’s been a while since I’ve done a project video on the channel and it’s not that I’ve not done any projects, I’ve designed lots of things this year it’s just that they’re part of my consulting business, under an NDA so they can’t be shared.
You may be familiar with the VoltLink, the usb to serial adapter that I designed a while ago, it’s quite popular on my Tindie store with lots of orders coming in and for good reason if you ask me, this is an awesome, reliable usb to serial adapter. To extend its functionality I also created this Shelly relay adapter which can be used to flash shelly relays, in a safe and reliable way by also powering the relay during the flashing procedure so you don’t need to have it connected to mains.
If you would like to order a VoltLink, you can find these on my Tindie store, there will be a link in the description of the video so check it out.
So far I haven’t any issues, not one single module with problems and I’ve probably made several hundreds of these. It’s a pretty simple design in terms of PCB, the components are 0603 so there isn’t much that can go wrong but recently I’ve started thinking about testing these.
Now the topic of test jigs and testing electronics in general can get pretty deep, especially if you need to implement it in the manufacturing process and keep track of the test results in an automated fashion but for hobby level it can be much simpler.
For example, depending on the number of units you manufacture, you can also skip testing all together, because if I sell 100 boards and 1 of them ends up defective, I can live with that 1 failure rate and I can cover the cost of shipping another board to that customer and all of this with zero resources wasted testing these but at the expense of one unhappy customer who needs to wait for another unit to be shipped.
So mainly for me that was the main factor for wanting to test these, to avoid having unhappy customers that might end up getting a bad unit. And I don’t really need to test for all of the things working, I just need to figure out if I have a working connection from the USB side all the way up to the shelly relay and also verify that the path can be used to communicate over serial and toggle the reset lines.
This kind of test would eliminate for example a lot of the most common issue like soldering problems with the USB Type-C connector or with the QFN chip, or with the PCB copper layers, or with the JST-SH pigtail connecting the adapter board, or soldering issues on the small adapter board so all of these would be eliminated.
So here is what I came up with, a series of 6 total shelly adapters, chained together in series with an ESP32 at the end of the chain. I would be connecting a VoltLink at the start of the chain, UART signal would then go through 6 of these adapters, connectors, pigtails and it would end up at the ESP32 side for either flashing the ESP32 or writing a small test firmware that would just communicate over serial to verify the whole chain is connected correctly.