Electronics

Rescuing vintage microcontrollers from their decades-long purgatory in a drawer.

PS: not my blog.

DIY rebuild project for the Tektronix PS503A dual tracking power supply.

The constructed power supply: https://www.paulvdiyblogs.net/2026/03/diy-ps503a-construction.html

PS: not my blog.

I barely know anything about electricity. With that said:

I bought this decoration containing a bunch of what looks like LEDs (henceforth "lamp") at a thrift store

It needs 4.5 volts to function, according to the writing on a little etiquette. I wanted to ditch the AAA battery power supply and power it with a DC adapter, so I stripped the DC adapters end and cut off the lamp's cord that goes to the battery case/on off button in order to connect them like so

I even tried to attach the stripped DC wires to the original battery box, thinking that maybe there some circuitry magic going on in the little PCB.

The LEDs do not light up.

Questions:

1. aren't this wiring of the LEDs weird? It touches itself all the way, which to my very limited knowledge means shorting itself. Unless LEDs work differently?
2. the wiring of the LEDs seems to be of other material than copper. Is that relevant here?
3. why isn't this working?

In any case, I'll just rip out the LEDs and put in my own LEDs with wiring that's encased in some insulator, I guess.

Edit: I needed to remove the insulating coating from the LED wiring ends. I did it by burning it off. Thank you all!

Do you need 16 bytes of ROM that you can program with a soldering iron? Well, you're in luck!

I'm working on a larger project that I'll hopefully be sharing here soon, and needed something to display hexadecimal digits on a 7-segment LED display. The non-obsolete ICs that I found could only do binary coded decimal, but I need to be able to display A-F as well. An EEPROM truth table can be used for this, but I also wanted to avoid any programmable ICs. I decided to take an old-school approach and create a diode ROM board.

Hello, first time poster (and also no significant EE background, so bear with me).

After receiving a batch of bad USB C PD trigger boards, I decided that it would be better if I made some myself. The design is taken from the CH224K datasheet. However, I am not sure if

1. the schematic is correct
2. the PCB is well laid out (I really struggled to fit everything)

Here is the schematic, and here is the PCB. Both are in a Codeberg repo.

I've been working on Ben Eater's breadboard 6502 computer project for a little while. The pins on the EEPROM sometimes get bent when I pry it out of the breadboard to reprogram it. I was afraid that they'd break eventually, so I looked into getting a Zero Insertion Force (ZIF) socket to put on the board, which should be gentler on the EEPROM's pins. Ran into a few problems though:

• The pins on ZIF sockets are too short to seat properly on a breadboard. They're designed to be soldered into a printed circuit board.
• I found a few designs for adapter PCBs that allow a ZIF socket to be used on a breadboard. They're all sized for the common green ZIF sockets, which take up a lot of extra space compared to the chip that they hold.
• Aries Electronics makes low-profile ZIF sockets that are very compact, but I couldn't find any adapters designed for them.

I eventually decided to solve that last one myself, and I figured I'd share the design in case anyone else might find it useful:

An audio amplifier was once a fairly simple analogue device, but in recent decades a typical home entertainment amplifier will have expanded to include many digital functions. When these break they are often proprietary and not easy to repair, as was the case with a broken Pioneer surround-sound device given to [Boz]. It sat on the shelf for a few years until he had the idea of a jukebox for his ripped CDs, and his returning it to life with a new main board is something to behold.

Internally it’s a surprisingly modular design, meaning that the front panel with its VFD display and driver were intact and working, as were the class AB amplifier and its power supply. He had the service manual so reverse engineering was straightforward, thus out came the main board in favor of a replacement. He took the original connectors and a few other components, then designed a PCB to take them and a Raspberry Pi Pico and DAC. With appropriate MMBASIC firmware it looks as though it was originally made this way, a sense heightened by a look at the motherboard inside (ignoring a couple of bodges).

[Kerry Wong] points out that the Uni-T MSO oscilloscopes have a logic analyzer built in — that’s the MSO, or Mixed Signal Oscilloscope, part — but you have to add the probes. He shows you how it works in a recent video below.

He’s looked at the scope’s analog capabilities before and was not unimpressed. The probes aren’t inexpensive, but they do unlock the mixed signal capabilities of the instrument.

Although simple logic analyzers are very affordable today, having the capability integrated with your scope has several advantages, including integrated triggering and the simple convenience of being able to switch measurement modes with no problem.

Breadboards are great, but as the world moves more and more to having SMD as a standard, prototyping straight PCBs is becoming more common. If you’re mailing off to China for your PCBs, it’s shockingly quick for what it is, but a one-week turnaround is not “rapid prototyping”. [Stephen Hawes] has been on a quest on his YouTube channel for the ideal rapid-prototyping PCB solution, and he thinks he’s finally got it.

Now, if you’re only doing single-layer PCBs, this is a solved problem. You can mechanically mill, or laser cut, or chemically etch your way to PCB perfection, far faster than the Chinese fabs can get you a part. If you want a double-sided board, however, vias are both a pain in the keister to do yourself, and a rate-limiting step.

Hi all!

I thought y'all might be interested in my weekend project: Using an ESP32 to read the value from my 121GW DMM and send it to my MQTT broker via Bluetooth and WiFi. This workflow is much better for me compared to logging to microSD cards. The code is an ESPHome config that can straightforwardly be flashed onto most ESP32 variants.

The config and some documentation is available here: https://github.com/tjhowse/121gw-esphome

A brief video explainer is here: https://youtu.be/GLtkTARH1eo

At the moment I'm only unpacking the main value, range and sign from the Bluetooth packet. It would be nice to read out the rest of the values, but I haven't felt the need yet. Note that the DMM briefly blanks the display when changing ranges. This results in a value of zero being sent on the MQTT link. All of my testing has been in volts mode, other modes may contain dragons! Please test thoroughly before relying on this for anything important.

Cheers, tjhowse

I built two circuits as similarly as possible 1) quad ua741 and dual NE5532. FFT on my Rigol scope showing peaks at 1k and 15k as set/expected (2 channels from Seesil generator are mixed with 1k signal at 80% of 15k signal amplitude) with this I believe I created a tool to do AM with my cheap Seesil generator and can also mix two audio signals.

That said, I have no clue what I am doing. I based my testing procedure off an Elenco radio kit.

So I guess I actually have two questions or areas where I am trying to understand better:

1. What makes one op-amp better than another? I am talking about the IC itself, I believe. Why is NE5532 better than ua741, I see and hear the difference, now why?

2. What should I be testing and/or what data should I be collecting to better understand and characterized?

Thank you for your time and consideration. I am 100% self-taught savage from the wilderness and stumbled into your camp, but we are not so different, I promise, just had to walk down different road in life. Thanks again.

Hobbyist/DIY guy in a garage. I use Linux. I have briefly tested Eagle and a couple circuit design apps but didn't like anything about any of them, did not spend sufficient time with them either, though. Eagle is going away? Any recommended apps for designing pcb and/or services? I am also open to more artisinal methods. What direction should I point my momentum? Not afraid to try things out but also not wanting to waste time. I have been breadboarding for a minute, learned to solder, benn making some pcb gadgets and think I am ready. Thank you. (Pic is audio mixer with two NE5532 and LM386)

Source: https://lcsc.com/product-detail/Vibration-Motors_Lian-Xin-Technology-XDMD-YB200-08_C47118014.html

Applying current changes the vertical position. You would glue a lens onto this and place it above your camera sensor.

Machine-translated page from the datasheet:

I am looking for a PMIC to power an ESP8266 with photovoltaic with a small solar cell ca. 2-5V. I had CJMCU-2557 in mind, but it is quite costly. Are there any other suggestions or experiences?
@electronics
#diy #elctronics

This is an update to this post about the typical applications of the first op-amp by philbrick: https://www.reddit.com/r/electronics/comments/1l1whsq/in_the_50s_george_philbrick_introduced_and/

I paid for this to be vectorized, so people could have it printed in any size and form they'd like.

Here's the vector graphic: https://8volt.at/poster-8volt.pdf

I've set up a spreadshirt store to be able to directly order it as a poster/shirt/sticker/mug/... with and without the 8Volt logo: https://8volt.at/store#!/all

Hey Lemmy! I found these on c/rightToRepair and thought you might like it.

https://www.ifixit.com/News/109137/a-guide-to-reading-ct-scans-part-1-what-is-ct

https://www.ifixit.com/News/109675/how-to-read-ct-scans-part-2-identifying-components

The SCD4x sensor from Sensirion measures CO₂, temperature, and humidity, and communicates these values via I²C.

The measurement principle for the CO2 is that of photoacoustic sensing. The fundamental principle is shown in the diagram below: shine light that the CO2 molecules absorb and use a microphone to listen to the pressure variations.

I ordered a batch of SCD41 sensors from China for various projects, including fermentation, mushroom and plant cultivation, and field monitoring.

Since I had extras, I sacrificed one for macro photography. I removed the cover with a dremel and pliers, then cleaned the internals using isopropanol.

Here is my take:

The temperature and humidity are measured by Sensirion’s SHT40, seen as the black square at the bottom right. It’s likely accessed by the internal microcontroller over an internal I²C bus.

The pink square at the top left is a MEMS IR emitter. The SCD4x datasheet doesn’t specify the emission wavelength, but 4.3 µm is standard for NDIR-based CO₂ detection. A similar emitter example is this one from Microhybrid. These emitters usually produce broadband IR, with a 4.3 µm band-pass interference filter on top. The pink hue likely comes from this filter. Filters like these are critical to target CO₂ absorption while avoiding spectral overlap with other gases. For further reading, see Infratec's application note and Delta Optical Thin Film’s technical explanation.

The gold component labeled “o119 ANC” is the MEMS microphone, used to detect pressure waves caused by gas molecules absorbing pulsed IR light—this is photoacoustic sensing. The vibration excited by 4.3 µm light occurs at ~70 THz, far beyond acoustic detection. However, the IR source is pulsed at a modulation frequency (typically 20–60 Hz, e.g. 40 Hz), and the microphone detects the resulting pressure variations at this frequency. The principle is outlined in patent US 2024/0133801 A1.

An example of a compatible MEMS microphone is Infineon’s IM72D128V01, which supports frequencies down to 20 Hz.

The final main component is the metal-shielded package. It likely contains a microcontroller responsible for:

• Driving the MEMS IR emitter with a modulated current (e.g., at 40 Hz)
• Capturing and analyzing the MEMS microphone signal to extract the amplitude of acoustic pressure oscillations (proportional to CO₂ concentration)
• Acting as an I²C master to retrieve temperature and humidity data from the SHT40
• Acting as an I²C slave to provide CO₂, temperature, and humidity data to an external controller

Here are top and bottom views of the sensor cap:

The cap has a circular gas inlet. The white material covering it is likely a hydrophobic ePTFE membrane, which allows gas exchange while blocking liquid water.

I hope someone else finds this interesting too!

EDIT: After posted this, I searched online and I found a photo from someone who went a deeper than me and did expose the microcontroller: https://www.hackteria.org/wiki/CO2_Soil_Respiration_Chamber

This is the photo borrowed from that site:

I was reading up on the life expectancy of different building materials when I came across this gem.

Screenshot is of page 122 https://www.portseattle.org/sites/default/files/2025-02/SEA-SIPP%20Technical%20Report%20Appendix%20C%20Life%20Expectancy%20of%20Building%20Materials.pdf

I guess the ethernet cables could last that long, but they rate house wiring to a lower lifetime. Ethernet cables are not "wireless", however.

The only other wireless systems I can think of are garage door openers, but they are definitely not expected to last 50 years.

cross-posted from: https://rss.ponder.cat/post/159054

Binner Makes Workshop Parts Organization Easy

We’ve all had times where we knew we had some part but we had to go searching for it all over as it wasn’t where we thought we put it. Organizing the numerous components, parts, and supplies that go into your projects can be a daunting task, especially if you use the same type of part at different times for different projects. It helps to have a framework to keep track of all the small details. Binner is an open source project that aims to allow you to easily maintain a database that can be customized to your use.

In a recent video for DigiKey, [Byte Sized Engineer] used Binner to track the locations of his components and parts in his freshly organized workshop. Binner already has the ability to read the labels used by well-known electronics suppliers via a barcode scanner, and uses that information to populate your inventory. It even grabs quantities and links in a datasheet for your newly added part. The barcode scanner can also be used to retrieve the contents of a location, so with a single scan Binner can bring up everything residing at that location.

Binner can be run locally so there isn’t the concern of putting in all the effort to build up your database just to have an internet outage make it inaccessible. Another cool feature is that it allows you to print labels, you can customize the fields to display the values you care about.

The project already has future plans to tie into a “smart bin” system to light up the location of your component — a clever feature we’ve seen implemented in previous setups.

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