Reddit:Electronics

I designed a simple board that lets you transmit audio directly from your computer onto the commercial FM band. no code, no drivers, just plug and play.

This was a fun personal project and not meant to be an actual product (you can find similar boards on AliExpress for around $5). It’s also my first ever SMD assembly, and it was pretty fun working with SMD components (SSOP was a bit difficult).

The board uses a TI PCM2704 chip to stream audio over USB from the host device. That audio is then passed to a KT0803 FM transmitter chip, which broadcasts it over FM radio. I added I²C breakout pins, which can be used reprogram the KT0803's settings like transmitting frequency, mode, and calibration parameters.

Github page for the project (Includes the demo with sound) - https://github.com/Outdatedcandy92/FM-Transmitter

I think I salvaged it from an old VCD player. Pretty cool.

Some background here https://antiqueradios.com/forums/viewtopic.php?t=306396

"Prior to the introduction of integrated op amps, it was extremely difficult to build stable DC amplifiers. By passing the signal through a chopper, the DC voltage can be passed through a feedback stabilized AC amplifier and then converted back to DC afterward. Chopper stabilized DC amplifiers--using electromechanical devices--have been around since the late 1940s at least."

"HP's photoconductive choppers eliminated the inevitable problems with contact adjustment and wear in the electromechanical ones, but they required higher input voltages to overcome the "on" resistance of the photocells."

Enjoy!

I always thought that if a circuit worked and passed basic functionality tests, you were good to go. But I’ve been digging deeper while working on a small consumer electronics project, and wow, there’s a whole other layer around safety, durability, and compliance that I hadn’t even considered.

Things like how a device holds up under voltage fluctuations, or how materials react to heat and moisture, all that stuff matters a lot, especially if you’re thinking about scaling or selling internationally. I know there are experts like QIMA who offer this kind of testing, and it’s wild how many factors are involved.

Makes me look at everyday devices differently now.

**image not mine**

Features
Has many gpio pins
Does the job
Custom 3D-printed Case
Based on STM32F103C8 microcontroller
USB-C interface
RTC (Real-Time Clock) capabilities
Embedded microcontroller; low power consumption
Check the REPO pcb and gerber files
As always
Thank you for reading this <3

Building a dual rail power supply 0-40v and didn't have any 4700uf or bigger capacitors so a row of 1000x2 + 680x2 + 470x2 + 330x2 + 220x4 + 100x2 for a total of 6 040 will have to do.

Just a heads-up: be very careful when installing software that asks you to disable or bypass your system's security features.

I came across this in the official documentation for the offline EasyEDA app — they explicitly instruct users to bypass built-in protections:

https://oshwlab.com/forum/post/3695f3a2f9694de4b1b4cfa839a9a03e

Am I the only one who finds this not just unprofessional, but a serious security risk. Especially for users who might not fully understand the implications.

Curious to hear what others think.

Can't get most chips in DIP anymore...

god damn those LGA packages

New old stock form my surplus lot.

I was modifying a cheap handheld oscilloscope to fit in my diy modular synth but the horizontal layout was a bit too wide for my liking so I did this to rotate the screen 90° ☠️

These were early version of mask roms from the late 70's if you remove the epoxy over the crystal they become Intel D2716 can erase them and program again.

Tons of IC's.. So Far 6.5 hours sorting and backing up programmable chips. I live Stream day 1 rather boring https://youtube.com/live/6U9ADQovUoY Day 2 Soon. I sorted out all the programmables near the end and will do another day of backups soon. Some devices were not supported on my Xeltek or i did not have the adapters. So i need to Bust out the BPM Microsytems 1710.

"Work in progress: rebuilding my Inovonics 222 clone using proper unsound construction techniques."

We don’t really do micro soldering at work so had to do it without a microscope. I did however seal the solder points with epoxy after testing for shorts.