Electronics Design

VoltLink Shelly Adapter Test Jig | Voltlog #426

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.

VoltLink revD USB Serial Bridge & ESP32 Programmer | Voltlog #414

Ever since I’ve started offering the option for the Shelly programming cable, lots of people have ordered one because it makes the job of flashing an otherwise dangerously mains connected relay very safe by not having to power it from mains, but just supply it with DC power from the VoltLink itself.

But this video is not about that, it’s about the latest revision D of the board, the changes that it contains and some future plans.

So as you may have noticed there is no power LED on the VoltLink and to be honest for my personal use case I don’t really need one but I do understand people that want a power status LED so that they get a quick glimpse of whether the board has power or not.

Personally I think that because the VoltLink is so reliable in operation, the power LED is redundant but I do remember the times when I was using other cheap usb to serial adapters, there were the occasional issues with the micro usb connectors failing, with the on board chip failing, so it was nice to be able to see that you still got power to the board at least. Nonetheless, I added one to the new revision, placed it right next to the USB connector.

Now because I added these two extra components to my schematic, the LED and the resistor, I decided to switch to a resistor network to replace 4 x 1kilohm resistors with a single package to further optimize my BOM cost and DFM.

Another small change I did was to bump the 4.7uF decoupling capacitor on the USB to serial chip to 10uF because I was already using that value at the output of the voltage regulator. This once again, optimizes my BOM for using less parts as this will become important later.

And while I was revising the PCB, I also switched to these nice labels created with the Kibuzzard plugin for Kicad. No extra functionality because of these, but they do look nice.

VoltLink revC CP2102N USB Serial Bridge & ESP32 Programmer | Voltlog #405

Welcome to a new Voltlog, a rather short video for today. I’m gonna be showing you the latest revision of the VoltLink USB To Serial Adapter. This is revision C and while this revision doesn’t necessarily bring any new functionality to the VoltLink it does optimize the design for manufacturing a little more which makes it easier for me to build these units.

Before I go into more details let me just quickly mention that if you would like to order one of these, they are available on Tindie and there will be links in the video description to the product page.

So like I mentioned, no new functionality added in revC, but that’s okay because I’m pretty happy with the functionality we have so far, I mean there is USB Type-C which means you no longer need to resort to the older micro usb cables, you got over current protection at 500mA, ESD protection.

We still have a high quality, high speed, usb to serial converter in the form of the CP2102N which enables baud rates up to 3M baud and this significantly improves the time you need to flash your board and you will quickly get used to this higher speed so much that when you switch to some other converter or board that only supports lower baud rate you will feel how slow that is.

We still have the 500mA rated low dropout regulator which provides 3.3V to the target board and 500mA is enough to cover the majority of boards that you will be programming. For example all of the ESP32 based boards that I design can be powered by the VoltLink while flashing firmware with no issues. Additionally I showed in a recent video that with a custom optional cable that you can order with the VoltLink you can safely flash Shelly relays without having them connected to mains voltage.

VoltLink revB CP2102N USB Serial Bridge & ESP32 Programmer | Voltlog #396

Welcome to a new Voltlog, a rather short video for today. I’m gonna be introducing this little guy. You might recognize the design, it’s my VoltLink USB to Serial Converter but in it’s latest revision B which has a few important upgrades over the previous one and these are things that I noticed while using the module almost daily so I think you will all agree with me that these were some good improvements that justified revB.

In general I tried to keep the board the same size, because I like this form factor, the arrangement of the connectors, the fact that I have my own VoltLink standard JST connector that i use for all of the boards that I design so all of that stayed the same but due to the ongoing chip shortage I had to pick a slightly different usb to serial chip, we are now using the CP2102 in QFN28 package. So generally this chip is very similar to the previous version except that it’s a bit newer but you still get up to 3M baud rates which is great. Because of the new chip this meant redesigning the passives to support this new chip and redoing the layout.

Also because of the ongoing chip shortage, prices for electronic components have gone up in the past year and I will have to run the numbers for this particular design but I have no choice but to increase the cost of the unit on my Tindie store if I am to continue making these.

I also upgraded to a USB full speed rated ESD protection diode with lower capacitance TPSP0503, this should mean no connection issues while at the same time offering the recommended protection level on the USB connection together with the PTC resettable fuse.

I Made A 10 Channel Thermocouple Data Logger – Voltlog #368

The idea for this project started when I got the T-962 reflow oven, after running a few tests I discovered that it had some hot-spots which meant some areas inside the oven were hotter than others and this could lead to trouble, you could get melted connectors in some places and cold joints in other places. Now it’s hard to tell how bad the situation is without doing some measurements so I decided to design & build this board which is capable of reading 10 thermocouples and logging the data. This way I could place the thermocouples inside the oven, something like a 3×3 or 4x2x2 matrix and I could get a sense of what’s going on inside the oven.

New Lab, New Voltlog Electronics Workbench | Voltlog #367

The most important part of this lab is obviously the workbench and this is something that I designed myself, I guess I can call this the Voltlog Workbench Design, it’s 2m wide with 80cm deep. The working surface comes out at about 95 cm from the floor. It sits on these adjustable feet but I haven’t even leveled it so far. Thanks to my friends at Welectron.com my working surface is protected with these nice premium ESD Mats. They are 100% and phthalates free, no bad smell, Heat and solder resistant, Chemical resistant, two layer ESD bottom side is conductive, top side is dissipative and they have this nice anti-reflective surface finish which is very comfortable to work on. I went with gray because it works best as a background for video shooting but you can opt for Blue as well. I’ll put a link to these in the description below, I highly recommend Welectron for their services & customer care and I highly recommend these ESD mats they are top quality.

Upcoming Projects Teaser – Voltlog #365

Welcome to a new Voltlog, for today’s video I want to share with you some of the projects I currently have on my workbench, these are projects that still need some work to be done before they can be published but this will give you a glimpse of what to expect in the upcoming weeks on the channel.

I have these 3 projects on my workbench, the first one is a multi channel thermocouple data logger device based on an ESP32. This has 10 channels based on the famous maxim thermocouple interfacing chips and all of those are read by the ESP32 and data can be logged on an SD card. This should help me measure the temperature inside the T962 reflow oven that I reviewed a while ago in a grid to check how the heat is distributed inside the oven. I’m pretty sure there are some hotspots inside the oven and some cold spots, I don’t know if there is anything I can do at mechanical/design level to correct for them but it would sure be nice to be able to know what’s going on inside the oven and with such a board I can just connect 10 of these cheap braided K-type thermocouples from aliexpress and hopefully get some consistent readings but more on this in a future video.

The next one is an FT2232 based interface which I designed with the main purpose of allowing me to interface via JTAG to FPGA boards. The chip itself is capable of other protocols as well but my goal here is like I said to interface to various FPGA boards. I plan to dip my toes into the FPGA world and try to get a blinky up and running on an FPGA board for a start. I have designed the board to include a voltage level translator because the chip is running at 3.3V but whatever you connect this to might be running at 1.8 or 2.5V so there is provision for that and it uses USB Type-C like all of the boards that I’ve designed in the past year.

The third project is an ESP32 based CAN development board that I plan to use in my adventures of hacking the CAN bus on my car. I should be able to install this into my car to intercept, modify or send CAN messages while at the same time having two outputs which I can use to control various stuff with on/off 12V power. It has a dc-dc converter on board to step down the car 12V to 3.3V to power the board and if I remember correctly the chip was chosen to have a wide input voltage range to accommodate for any potential spikes on the 12V rail of the car.

How To Create High Voltage Isolation Slots In Kicad – Voltlog #364

Back when I published the video on the aquarium controller I built, someone asked how are these high voltage isolation slots or cutouts done in Kicad and I thought I’d do a short video to explain how you can design these into your next project but first, let’s talk about their purpose and whether or not you need them.

There is a common confusion between the terms creepage and clearance, myself I’m guilty of sometimes making this confusion but to give you a clear view on this, I found this picture online which shows everything very clear. Spacing between conductive elements through air is clearance while Creepage is spacing between conductive elements over an insulating surface.

By adding these cutouts in the PCB we are only increasing creepage distance, but if you would also like to increase clearance you will need to add some kind of barrier, and this is usually built into the enclosure and it will slide through the slot creating a barrier to prevent any potential high voltage arc to jump over the barrier by increasing the length.

There are also secondary purposes for putting cutouts into your PCB, I have used them in the past to create a thermal barrier or to accommodate various enclosure walls and features but I won’t talk about those today, those applications tend to vary a lot on a case by case basis.

But if you are using them as high voltage isolation you need to be aware of some aspects: first and most important remember to make the slot at least 1mm wide, if possible go with 2mm as this is required by some standards. There is a min width required by the fab house anyway because they are going to use a router bit on a CNC machine to cut that slot into the PCB and this may vary from one board house to another but I’ve seen 0.8mm mentioned by most PCB manufacturers. For example PCBway which is the sponsor of the channel, gives a min value of 0.8mm non plated slot and 0.5mm for plated ones. For isolation purposes you only want non plated ones.

There might also be other limitations on the size of the corner radius, I’ve not hit any of those so far myself but just imagine that router bit going around, it will not be possible to create very small features at your request.

Use These LEDs For Your Next Project – Voltlog #362

Welcome to a new Voltlog, this will be a rather short video where I will be talking about a rather common subject, LEDs. I’m sure everyone uses them in their projects but if you are like me you probably never cared about the efficiency of the LEDs you use for signaling the status of something on your microcontroller board. So what I was doing most of the time was picking the least expensive LED available while still picking a known manufacturer like Kingbright or Lite-on or Osram just to avoid quality issues. And that was my voltage rail indicator LED or my blinky LED for signaling some status. But this ofcourse meant I needed to drive those LEDs with a fairly high current of 15-20mA to get decent brightness out of them and that might be OK for numerous applications but in this video i want to talk about high efficiency LEDs and how your project could be nicer because of them.

ESP32 Aquarium Terrarium Controller – Voltlog #361

This project started when a friend of mine which has a snake terrarium asked for my help to build a system that is capable of regulating temperature and humidity so the snake can live in optimum conditions. I’m not necessarily a snake lover, I would rather stay away from these kinds of creatures but that doesn’t stop me from helping my friend.

I started by figuring out what he uses to control temperature and humidity and it turns out there is some sort of a lamp to provide heat from above, some sort of mains powered stone that heats up and a water fountain, probably one that runs with fog to control the humidity. All of these are mains powered and only need simple on/off control which makes things simple when designing the electronics board.

In terms of digital control I figured it would be nice to have to be able to update the set points and check on the status values wirelessly so I went with an ESP32 modules. This also helps to add an extra layer of protection to keep the user away from the dangerous mains voltages present on the relays. I can have the whole board, enclosed in a plastic box so the user never goes near the mains voltages.