Meetup report: 17 May 2018

TL;DR: 3D printers, robots and Sonoffs.

My Sonoff Basic Wifi switches arrived! My evening was spent getting them working and set up the way I wanted.

First step was to connect them and get them going with the stock firmware. I downloaded the EWeLink app and got one of them working.

That done, they needed to be reflashed with OS firmware.

Tasmota looked like the most complete firmware for the Sonoffs. It also had one BIG advantage: OTA (Over The Air) updating from the stock firmware to Tasmota! No need to open up and solder extra pins to the devices.

I used the experimental OTA update method and it worked perfectly. Luckily the factory firmware was still a slightly older version. The newest versions don’t work with this method.

Spoiler alert: Over the weekend I got Home Assistant running on my Raspberry Pi to integrate these switches as a home automation solution.

I let the 3D printer run in the background on a print job or 2, just to visually test the bed movement. As I suspected, right at the top of the travel, the bed moves sideways as the print head moves. This sloppyness is probably a combination of the Z-axis standing on a non-stuck-down base and the fact that the spectra line is not aligned correctly, which shows up particularly at the top of its travel. Some manual tweaking should fix this.

I let the pendulum wave run for a while and took some better photos of the waveforms.


Otto also worked on his printer. The print surface was not flat and calibrated, so with some effort he got the bed leveling to work.

Jan had some good inputs to add on all our projects, and helped Steph with his Alphabot. Looks like the screen is a 2-color OLED, and works as advertised, mostly.

An interesting evening, will do again.

Meetup report: 10 May 2018

TL;DR: Interesting evening, and we’ll do it again this Thursday.

The tables

Earlier in the week, I managed to redesign the pendulum ball holders to snugly fit the magnets in place, as well as being a bit more springy an nicer-looking. My mission for the evening was to print out a few examples and tweak until happy. I did get a few prints, but the bottom layers are squished and misaligned, leading to a misshapen print that did not fit that great. I think I’m overextruding.

Some prints

I also tried a newer version of Cura, but that resulted in skipped steps which messed up the last print I did.

Otto's rfid indicator project

Otto brought a very interesting project he’s doing for a friend: An ESP32 with OLED screen and RFID reader integrated into a handheld tool, with a Mutitoyo indicator attached. The idea is that this is used to make measurements easier. The user would position the indicator at a specific point and then scan an RFID tag near the point to capture the reading. The tag also stores the allowable range of readings to indicate a pass or fail. The ESP32 also serves as a web server to automatically transfer the readings to a central database. This eliminated manual entry errors and makes the whole process faster.

We discussed placing of a possible RFID sensor for home entry. Putting it into the mains power meter box seems a bit risky and uninsurable. However, the front gate has an extra access plate which is accessible and probably has 12V power already, so it should be pretty easy to wire in there.

Bob the Biped

Tom and Steph worked some more on the Alphabot. Not sure what they managed to figure out.


Ruan brought a disassembled smoothie maker. He is hoping to use the motor to make a wood lathe. We figured out how it’s controlled and came to the conclusion that the motor was probably too fast and had too little torque for a direct drive.

Triac for speed control

He then worked on the square tube layout for the lathe.

Lathe design

All in all, a nice evening.