Hello! I wanted to show off my ongoing project.

It's a diy colorimeter (a device that measures the true color of things) with high precision. Since it is based on an AS7341 10-channel spectrometer, it can also provide a very coarse spectrum, which is especially useful for me, because it allows me to analyze dying strengths and concentrations based on the Kubelka-Munk mechanism.

Similar devices can be bought, but they cost in between of 200-2000EUR, which I am unwilling to spend. Plus, this has been a super cool project in the overlap between programming, 3D-printing, functional design, electronics, colorimetry, chemistry and (at least for me specifically) natural dyes.

My device is able to achieve a relative precision of about 0.1-0.5 delta E (relative color difference in the CieLAB color space), depending on the area (blues are a bit noisy, and pinks are generally difficult). I have spent 200-300 Euros on it so far, but if I wrote down a BOM of what I got now and know to work, it would be at most 100EUR.

It consists of:

• An Adafruit AS7341 Spectrometer (the AS7343 should also fit with no hardware changes necessary and only minor software changes, adding 2-3 more channels)
• A single Nichia Optisolis LED, shining in 45 degrees onto the sample
• An ESP32-C3 Zero from Waveshare doing all the thinking & data storing
• An 0,96" OLED screen with SSD1306 driver
• A small hand-soldered PCB
• A couple JST PH cables and sockets
• 2 small buttons
• A 3D printed body
• A couple of M2x6 screws and M2 press-in inserts
• A cheap 700nm 9mm IR-cut filter
• An even cheaper piece of polarizing plastic sheet for LCD displays

I also built a surprisingly good beam trap from an IKEA steel bottle and some black fabric. And a relatively good white reference from some wound up and compressed PTFE-tape.

The software includes all the logic to communicate with the sensor, doing repeated and series measurements, performing calibrations, exporting measurements via serial connection and Bluetooth, presenting the measurements as reflectance spectra with NIR corrections, and conversion of the spectral data into common color descriptions like CieLAB and RGB (if possible).

One remaining issue is absolute calibration. "Absolute white" samples made from compressed and fused PTFE or BaSO4 powder is expensive, and calibrated color sample cardboard cards cost like 70EUR and would only be necessary once. And they don't help with calibrating the spectral data, only the colors that come out of it (the correction matrix would basically counter the spectral errors, and these would remain unreliable). I was thinking of using 3D-printing-filament swaps from reputable brands, with specified printing settings and careful sanding as calibration standards and even relative white references, but that would need someone to fabricate such a sample to specification and put it into a proper spectrometer and share the data.

I was thinking of open-sourcing the print-files, the software and the wiring diagrams if there's enough interest for it. Reproducing it should be way easier than building it for the first time (don't ask how much time I've spent optimizing the light paths), and if more people contribute, this could actually become a really awesome distributed project.

Safety Disclaimer: I am fully aware of the hazards regarding high-power UV light. The chamber is structurally sealed, I use dedicated UV-blocking safety gear during testing, and a hardware safety switch will be installed to cut power instantly if the door is opened.

Hi everyone!

A couple of months ago I decided to start building some custom IEMs myself. The commercially available UV curing enclosures did not satisfy my needs, and very few of them would go into a required wavelength territory for Dreve Fotoplast and other suitable resins. Just wanted to share my build and get some feedback.

Why not pre-built?

It's mainly prices and availability. Most of the 365 nm UV curing units are for medical purposes, and the vast majority of those still use fluorescent lamps because of some certifications (or whatever). This is inefficient and expensive to maintain.

The enclosure

I repurposed a solid cast aluminum chassis to act as both a rigid body and a massive passive heatsink for the internal high-power UV LED emitters (Seoul Z5, 365 nm). To power these 4 pairs of diodes, I used Mean Well LDD-500LW drivers. Every connection possible is made with silicone-insulated wires, so they do not degrade in UV light over time.

In order to avoid using a turntable, I had to add aluminum tape, and it worked flawlessly: there is no shadowing.

It also turned out that this setup is so powerful for its purpose that it would make UV resin boil. So I had to add a controller.

The controller

It is based on the RP2040 Pico board at its heart. The LDD-500LW allows one to use PWM to control its maximum output power (white wire). When this wire is connected to V- (GND), the drivers are off, and they are at their 100% power when this wire is NC.

To control the LDD driver with the RP2040 in a direct way, I had to use a two-transistor setup (BC547 BJT and IRFU9024 P-ch MOSFET). Since my input is 15V DC, I had to also add a DC-DC converter and use a voltage divider not to fry the LDD with 15V.

The SSD1306 OLED screen and the EC11 encoder were added to control this thing somehow and get feedback on what's going on. The screen shows current power and curing time. During the "work" mode, any encoder action would stop the process immediately. I have also set a hard limit of 3 minutes of continuous work time, just in case.

First results

I was able to get a consistent, reproducible shell after 14-16 tries. Curing faceplate templates is still tricky because I wanna get them as thin as possible, and they would bend without proper temperature stabilization.

Advice needed on

• Door hinges. It seems like I need offset ones. Which designs (3D printed, preferably) would fit here the best?
• Door locking. Because I have a "paracord gasket" to prevent light leaks, I cannot place any kind of locking mechanism inside. It seems to me that some kind of a magnetic latch should work, but again, I cannot find out the exact way of implementing this.
• Wire management. Any tips on how to clean up the wiring inside the box?

I've been building a large equipment cart for video production, and after adding batteries and motorized wheels, the thing can weigh nearly 400 lbs loaded.

The original cable brakes that came with the wheel kit were not going to cut it.. so I decided to integrate a custom hydraulic disc brake system into the forks I had fabricated for the brushless wheels.

It was my first time working with hydraulic brake lines, and took quite a while to find parts, and to design a "one brake lever" solution. In the end It works pretty well with the exception of the parking brake feature: whenever I leave it engaged the whole system loses it's ability to function correctly. There is no fluid loss. My suspicion is that when the lever is held in, there is a small amount of oil that is able to bypass a seal in the handle assembly, resulting in less fluid in the line side. Anyone have any insight about this?

I documented the build here if you are interested in following the build:
https://youtu.be/Xz3B-3wACwE

Right Your Ship Captain carved in birch. In this seen there is a person on the deck of the ship with their arm held out, the sails are inflated. But their ship is under water, the anchor is down, the fish are looking at them while the world is going on with out them. This carving talks about the determination to go in the wrong direction when everything is against you.

I'm pretty happy with it but we don't really use it that often.

I plopped a monitor in there and I tapped into the (annoyingly and needlessly complicated) wiring for the buttons. I connected the buttons to zero delay usb encoders and then setup fruitbox to accept those button presses as letter/number/button inputs.