Reddit:Electronics

I tested my KY-013 thermistor, which I bought as part of a sensor kit. At first, I thought it was defective, because when I tested it the input always returned 0 bits of resolution. I tested two other sensors from the KY family that came in the same kit, and the same thing happened.

Then I had the idea of swapping the ground pin with the signal pin — and boom! It worked. Apparently, in the production of the modules I bought, the signal and ground pins were swapped (that’s what you get when buying from a questionable supplier).

The supplier didn’t provide a datasheet for any of the components, nor information about what each one did. So I had to rely on some help from ChatGPT. I managed to identify all the components and created documentation in Notion with images and names so I wouldn’t get lost again. Document your projects, folks.

I’m using Notion to centralize information related to real-time systems, electronics, ESP32, and Arduino, mixing all of that into a broader firmware study.

I also took the opportunity to test whether the voltage returned by the circuit matched the actual measured voltage. For this, I used my DT-830Y multimeter. The measured value was around 1.51 V, while the value shown on the serial monitor was 1.1 V, which resulted in a considerable error. So I added a correction factor to the voltage calculation. Below is how the function ended up.

This correction factor is not precise; I would need to run the project more times to compute a more accurate arithmetic mean. The error is around ±1.5 °C for temperature and about 0.5 V for voltage, which is reasonably low.

Now I’m going to stop focusing on the KY-013 and start testing other sensors, creating code bases like this one. If anyone has ideas for portfolio projects using the KY-013, I’m all ears.

Conclusions:

• I won’t buy from questionable suppliers anymore.
• Is using a correction factor for voltage a hack, or the art of engineering?

I built a compact wireless power bank as a personal project to explore power management, protection, and layout tradeoffs in a small enclosure.

The system is based on a single-cell Li-Po with a dedicated PCM for overcurrent/overvoltage protection, a USB-C charging module for fast recharge, and a boost converter to supply the wireless charging module. A physical slide switch fully isolates the boost and wireless charger when off, so there’s no standby drain from the battery.

One of the main challenges was balancing size, thermal behavior, and efficiency. Wireless charging is obviously less efficient than wired, and this version does get warm under higher load, so the focus here was more on validating the architecture and enclosure layout rather than optimizing efficiency. Thermal and efficiency improvements would be a priority in a future revision.

The enclosure is sized tightly around the electronics and uses a transparent lid mainly for inspection and layout verification during use.

I documented the full wiring and build process in an Instructables write-up for anyone interested in the details:
https://www.instructables.com/LucidCharge-a-Slim-Transparent-Wireless-Power-Bank/

Happy to hear thoughts or suggestions on power architecture, thermal handling, or protection choices.

I’ll open with the project’s biggest criticism from everyone around me: yes this thing does require working SIM, which means money, which means the project has a recurring cost component.

It was built at the launch of Pacific Bell Mobile Services (PBMS) later Pacific Bell Wireless (PBW), Cingular and AT&T – the first GSM network on the west. As soon as I got the phone, texting immediately caught my eye. The project receives SMS commands and flips GPIOs to control a 24v Patlte tower via Opto22 – like those you see on a factory floor machines. Simple commands are texted to the phone number of the SIM inside the Wavecom module: yellow on/off, red on/off… and it replies with “done”. Now the Arduino context: the board is an early Futurelec ET-JRAVR with AT90S2313, firmware upload with PonyProg. Code you ask: Notepad and GNU GCC – hassle galore, however imagine the Star Wars-like magic of texting on your Nokia 3310; hitting send and in few seconds the tower lights up! Forget the dot-com crash; and S&P carnage. Just look at that cute little 1.9GHz GSM antenna (the only GSM band at the time), got it at Weird Stuff Warehouse.

And yes, I was a big fan (still am) of Opto22; I have boxes with hundreds of modules; love them yellow, white, black and red!

3D printing is such a fascinating field of technology, so a couple months ago, I decided to take a deep dive and learn how they actually work!

This took me to one of my very first PCB projects, a small, cheap, 3D printer motherboard. While it's not the most cutting edge board, I learned a lot and I fully documented my process designing it (https://github.com/KaiPereira/Cheetah-MX4-Mini/blob/master/J...), so other people can learn from my mistakes!

It runs off of an STM32H743 MCU, has 4 TMC stepsticks with UART/SPI configurations, sensorless/endstop homing, thermistor and fan ports, parallel, serial and TFT display connectors, bed and heater outputs and USB-C/SD Card printing, all in a small 80x90mm form factor with support for Marlin and Klipper!

Because it's smaller and cheaper than a typical motherboard, you can use it for smaller/more affordable printers, and other people can also reference the journal if they're making their own board!

If I were to make a V2, I would probably clean up the traces/layout of the PCB, pay more attention to trace size, stitching and fills, BOM optimize even further, and add another motor driver or two to the board. I also should've payed a bit more attention to how much current I would be drawing, and also the voltage ratings, because some of the parts are under-rated for the power.

I just got it running after a bit of bodging and I plan on using it to create a foldup printer I can bring to hackathons across the world!

The project is fully open source, and journaled, so if you'd like to check it out it's on GitHub (https://github.com/KaiPereira/Cheetah-MX4-Mini)!

I absolutely loved making this project and I'd love to hear what you guys would want to see in a V2!

This is a project that's been in the works for a while, I had been trying to find more compact and portable compute options for various projects and eventually settled on making my own carrier PCB for the CM5 which fullfills my needs. It's fully opensource so please do check it out!

https://github.com/azlan-works/Argo

https://oshwlab.com/azlan777/argo

When I tested this board I thought that I had designed it wrong, so I cut 19 traces (in the upper left corner) and rerouted them with patch wires. But it turned out that it was right from the beginning so I had to re-solder the newly added wires to restore the original configuration. A lot of soldering just to uglify the board...

Carpenters have this rule "Measure twice, cut once.", maybe electronics engineers should have something similar like "Test twice, don't patch" ;-)

WARNING! High voltage AC and DC on hot side of this circuit. Do NOT attempt to build any SMPS if you are a beginner. You need at least simple LCR meter and high-voltage oscilloscope probe for tuning. Caution is advised!

One of two higher power supplies that I need for my projects, this one is largest made by me. Transformer is a custom made also at home. Circuit and transformer design schematics in gallery.

Introducing Open-Schematics: largest public hardware schematic dataset, paired with images.

WIP screenshots for some RP2040 based cyberpunk sunglasses I've been working on this year.

Hopefully someone will one day create a kicad or easyeda extension that allows me to route at 30° / 60° angles, so I can make hexagonal traces

Third image is the first version. First and second images are improved based on feedback from my dad that has a lot more experience with electronics than me XD

This was possibly the most fun school project I have worked on, even if it was slightly more programming than wiring it all up

One of 4 Automated PCBA test fixtures I have just completed, entire design is from scratch and pretty much everything you see is 3D printed or Laser Cut!

I have 2x PCBAs inside, lots of wires and an additional switching PSU with Dummy load to simulate a battery for the UUT!

Hello, this is a radiophone project I'm working on while in my second year of ECE.

I came up with this new design this time on 4 layers as impedances are really smaller.

First part of the circuit (bottom left) is an LC that will tune close to 1Mhz using an old-school variable capacitor. On next the signal gets demodulated, amplified, given power and outputted (bottom middle) and the rest is a simple power rectifier, with an IC for a cool volume bar using LEDs

Pics are in order of layers, I used GND/SIGNAL - GND - POWER / SIGNAL - GND, and keepout zone below the transformer in order to remove capacitive noise.

Schematics

Layer 1 gnd/signal

Layer 2 GND

Layer 3 power/signal

Layer 4 gnd

This is a small laser module built utilizing a laser diode recovered from a DVD burner. The power supply is based on a ST Microelectronics LM317T adjustable voltage regulator set up in a constant current configuration.

Picture 3 is the output next to a ~5mw laser pointer output. don't think my phone camera liked taking this picture.

Schematic included.

Why the F did they decide to. No, no lissen, we need 36 different pinouts on the same ic with no id code on it either making it impossible to know wich "style" ic you got. Now that's what we need. Looking for help to identify GDS on the nmos somehow cuircit or instrument no problem.