Reddit:Electronics

This was a project that I worked on a couple months ago that was really fun and cool, I followed it on YouTube if you look up adhd engineer. (Black was the first version)

Made a full adder with CSD15380F3 N channel FETs and 0402 resistors. I probably won't actually get it made.

For my home theater controller i use an existing obsolete hmb2260 settop box and keep the 4digit display as its integrated in the casing. so an arduino nano can display info on it. The ltc display is common anode and its multiplexed. I used an mcp23017, register b outputs are connected to each segment (7seg +dp), via uln2803 darlington transistor ic. The anode of each digit is switched by a 2n3904 as this transistor can switch the required current (8x25ma=200mA max). This transistor is switched via 1k resistor by register A of the mcp. So via i2c, only 1 digit is powered at the time resulting in the current flow from 5v supply, via 2n3904, via led segment(s), via 180 ohm resistor, via uln2803 darlington, to ground. I could by software in the arduino switch each digit in a row every 20ms without seeing a flicker. So it works quite well.

Here's something I hooked up at the weekend - it's a prototype for an NFC card reader door entry system, with buzzer and doorbell I/O + lock strike plate activator. The ESP32 is running Tasmota and the board speaks to Node-RED via MQTT over wifi.

Astable multivibrator LED ckt

Using a arcadyan hmb2260, just keeping the case and the connectors ,ir sensor and display. Grinding off all smd components of the original multilayer board. Keeping the scart,ca display,and other connectors. Adding arduino nano. Building display controller with mcp 23017. Implementing i2c bus between nano and mcp. Next a second nano will be added, as i2c slave to control hdmi cec bus. Aim is to control the home theater by sending cec commands, controlling line audio and speaker relays.

Greetings everyone!

This is a follow up post on a previous one I made a month ago regarding an remote-controlled car project using an L289N motor driver with an ATMega328P microcontroller and an NRF24 module to communicate. I've been re-reading the comments and I added the necessary changes that needed to be added. An idea I have in mind is to add an Adafruit OLED screen so as to keep track of battery life or something, but I want to get the basics down first before I do that. I am open to additional feedback.

Added changes :

- To begin with, better-organized schematic (with the Ground symbol facing down this time hehe) with explanations.

- Ground plane on both front and back so as to reduce noise.
- 220 uF capacitors on both 5 Volt and 3.3 Volt regulators, as well as 10 uF capacitor for the NRF24 module to further reduce noise.

- Added a 10k resistor from 5v regulator to RESET pin (Pin 1) of the ATMega328P. In my previous project I did not have this, and was worried that my project would not work because of this mistake. Luckily nothing happened but in this newer project, I added the resistor just to be sure,

Thank you once again!

JLCPCB is great for prototyping. But I'm writing this to warn anyone considering using JLCPCB's assembly service for projects involving digital MEMS microphones. I've tried 6 times over the last two years. It has cost me countless hours, endless frustration, and over $2000. Since I do this work for a non-profit organization protecting elephants, the setbacks hurt even more.

The PCB is for a wildlife audio recorder – basically a digital MEMS microphone connected to an ESP32. Nothing particularly complex.
EDIT: The MEMS mic we use is the ICS-43434

Here’s the timeline of what happened:

Order 1 (Apr 2023): For prototyping, I ordered 2 assembled PCBs. One MEMS microphone arrived broken. Neither JLCPCB nor I knew why initially. I spent hours troubleshooting. I specifically asked their support if they followed the correct reflow temperature profiles and if they performed board cleaning (which can destroy these mics). They replied that temperature curves looked good and claimed no board cleaning was done.

Order 2 (Aug 2023): Thinking the first failure was a one-off, I ordered 10 PCBs. To my disappointment, 8 out of 10 arrived with broken mics that only recorded noise. Adding an external mic to the same PCB worked fine, confirming the onboard mics were the issue. This time, I removed the cap from the MEMS component and could see the ruptured membrane (See picture). Some also showed bad solder joints. A friend suspected the mic was too close to the panelization rails, causing stress when the rails were broken off. So, for the next design, I moved the mic further away and added a gap to the rail area.

Order 3 (Dec 2023): Confident the rail spacing was the fix, I ordered 50pcs. All 50 arrived broken. Again, I opened the MEMS packages with a hot air gun and saw the membranes were shattered. After endless emails, JLCPCB initially offered a tiny coupon of 20USD, which was insulting given the scale of the failure. Eventually, after significant back-and-forth, we settled on $120. I asked how to prevent this, and support told me to add a specific note to my next order asking for extra care.

Order 4 (Feb 2024): Following their advice, I ordered again, adding the requested note. Nothing changed – all boards arrived broken. Finally, JLCPCB started investigating properly. They used some of my parts from stock to test their process. And YES, they found the issue: their board cleaning process destroyed the microphones. Specifically, dry ice cleaning after manual soldering was the culprit. Apparently, they do perform cleaning sometimes (especially with through-hole parts), even if you explicitly told them not to.

Order 5 (Nov 2024): Armed with JLCPCB's own findings, I explicitly added a remark for my next order of 100 boards ($1500): NO dry ice cleaning without protection. I was reassured by support that the special request would be followed. When the boards arrived... All 100 were broken again... due to dry ice cleaning. JLCPCB admitted their operator failed to follow the instruction. I received a $200 coupon after a long negotiation.

Order 6 (Mar 2025): I had almost given up but placed another small prototype order (5 boards) and decided to give the mics one last chance. I wrote the note again: "NO DRY ICE CLEANING or it will destroy the MEMS". I also confirmed with support that the note was in the system and would be followed. When they arrived... No surprise: all membranes broken again, due to the dry ice cleaning process.

After this final failure, I told them I was done with JLCPCB and would have to share my experience. Only then did they offer to refund this last order completely, which i refused. That's not how it should work.

Based on my documented experience, JLCPCB seems incapable of reliably assembling boards with MEMS microphones or consistently following critical process instructions. If your project uses MEMS mics, I strongly advise you to consider alternatives or proceed with extreme caution.

Hope this saves someone else the time, money, and frustration I went through.

I have to say that the support contact I had (Emma) was always friendly and tried to be supportive. However, it felt like crucial technical details sometimes got lost in translation when relaying information between me and the engineers.

I reverse-engineered a no-neutral smart switch from Sonoff. It's like 70% ready, not all values for passive, no MCU board, no PCBs. If someone is interested in collaboration, let me know.

I finally got rid of all those cards I had in my nightstand for years😩

It finally made it work

I had previously done it on two breadboards, because I had to find space for the push-up buttons, but yesterday I received this type of buttons😄

Hi