Electronics

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.

From Blog – Hackaday via this RSS feed

I've gone through a bunch of different anti-static mats, but they are always lacking, or sticky, or smelly

What makes the ideal anti-static mat for you? What is your favorite?

How do you usually ground your mats?

nice kind of violence tho

You can do all sorts of nifty things when you're designing silicon. Including this abomination.

https://en.wikipedia.org/wiki/Carcinisation

Source: datasheet for LM161, a high speed (20ns delay) moderately high voltage (30V) comparator. I'm going to try and make a discrete version of some bits of it and see how well it works. Maybe not this triple-emitter NPN though, I draw the line at components that require livestock sacrifices.

FR2 is the brownish material that many cheap circuit boards are made of. It's a mixture of phenolic resin and paper. Apparently it's quite useful to make gears out of:

Phenolic Gears exhibits superior shear force, help reduce machinery noise, absorbs destructive vibration unlike metal gears, phenolic is non-conductive, protects the mating metal gear train, and are known to outlast metal gears under severe continuous service. (source: https://www.knowbirs.com/phenolic-gears )

(Main pic stolen from here)

(Many more pics here)

Has anyone seen these used anywhere? I've read a hint regarding pool equipment, but I have never seen them there. I assume the fibres allow them to last longer than plastic/resin only gears.

Two different sizes shown. Each has two inductors (grey bits) stuck to a capacitor (middle) with some metal end caps acting as terminals. There is a third terminal underneath the capacitor. Grid in background is 1mm, pics stolen from LCSC.

I think this taped picture is also really cool (stolen from here):

Datasheet: https://www.murata.com/en-global/products/productdata/8796766699550/ENFE0002.pdf

This is UV sensitive solder mask resin, applied as thin as possible using a silk screen mesh. Afterwards it's heated at about 90C for 10 minutes. This makes it more sensitive to UV light by evaporating most of the solvent.

It is exposed with a 405nm laser at about 250mw of power. I intentionally unfocused the laser for a spot size of about 0.5nm

After exposure the pads are easily cleaned off with some IPA.

der8auer got the original 5090 card from the reddit melting cable post, then demonstrated that two of the six 12V power connector cables are having 20ish amps running through them and overheating, while the other 4 cables are not.

The thickness of the board beneath it gives deceptive scale. It's about 50mm tall and the toroid is 85mm in diameter.

https://www.lcsc.com/datasheet/lcsc_datasheet_2408061709_Ruishen-RSCM11548-5mH-3P_C37634003.pdf

I was looking for much smaller CMCs. Also the datasheet for this part doesn't have impedance-versus-frequency graphs so I refuse to buy it anyway :P

A open source home automation mobile robot arm!

Exploiting the promise of recent advances in imitation learning for mobile manipulation will require the collection of large numbers of human-guided demonstrations. This paper proposes an open-source design for an inexpensive, robust, and flexible mobile manipulator that can support arbitrary arms, enabling a wide range of real-world household mobile manipulation tasks. Crucially, our design uses powered casters to enable the mobile base to be fully holonomic, able to control all planar degrees of freedom independently and simultaneously. This feature makes the base more maneuverable and simplifies many mobile manipulation tasks, eliminating the kinematic constraints that create complex and time-consuming motions in nonholonomic bases. We equip our robot with an intuitive mobile phone teleoperation interface to enable easy data acquisition for imitation learning. In our experiments, we use this interface to collect data and show that the resulting learned policies can successfully perform a variety of common household mobile manipulation tasks.

Hello everyone, I recently built a small distribution board to distribute 5V to multiple components for use in a robotics project. I made each output switchable with an individual switch and an LED to indicate the current state. When I went to test it using a lab power supply I noticed that the LEDs would start flickering weirdly when I turned them off and on again.

https://imgur.com/a/zaSCUby

As it turns out, the LEDs, which I found in my dads old parts in a bag labeled TLBO 5410, are apparently blinking LEDs. I found a datasheet for TLBR5410 LEDs which seem pretty much identical to what I have accidentally used.

Apparently these LEDs are made to operate directly from a 5V supply without an additional current limiting resistor (it is already built in) and are made to continuously blink at a frequency of 3Hz.

Because I thought I was using standard LEDs I added a series resistor causing them to behave weirdly due to low voltage. For comparison, this is how they are supposed to act: https://imgur.com/a/fXlcEDs

Me a few days ago, shopping on Amazon: "All the component and jumper wire leads are going to be on the bottom anyway; why shouldn't I get a pack of single-sided breadboards for $6.25 instead of double-sided ones for $10?"

Me today, after having lifted three pads off the damn board in 10 minutes: "Oh, that's why."

Get the double-sided breadboards; they're worth it.

4 bit adder. Took me a few evenings this week to put together. Im quite happy that it worked first try without any bugs. Constructive criticism is encouraged.

Im just getting back into building circuits on my breadboard and I want to know if there are any tips from the pros on here to help me on my journey. Also some links to resources for projects would be nice.

Cheap Chinese devices have iron instead of copper in wires. Aluminium is not suitable, since you can't solder it, otherwise I'm sure they'd use that as well.

Don't be fooled if the strands are copper colored, that could be either varnish or a thin layer of electroplated copper. A magnet test will reveal the truth. If it can't be soldered, it's most probably Aluminum. I've seen that as well, but only on wires that use some sort of a clamp-on connector at both ends... basically, it was never meant to be soldered.

i couldn't upload a video so it's a link