Meetup report: 31 May 2018 (And the previous week)

TL;DR: Knock sensors, ATTINY85, Satellite antennas, huge 3D printers and some drawing machine stuff.

Successful lissajous test

Last week

First, a quick report on last week: Steph did the Arduino knock sensor tutorial, but it looked like his piezo element was not working. We tried a few of mine, but most were actually buzzers, which don’t work in this application.

Evert came by: He’s interested in an IOT project with remote sensing, so we talked through the options, paying attention to the power requirements of the different technologies. This is very dependent on the data rates and radio technology used.

I messed around with the 3D printer and started getting my drawing machine going.

This week

Hard at work

Otto worked on his portable 3D printer, getting some misalignment sorted out. He had prints on the SD card, but most of them were sliced with ABS filament settings. PET-G needs a much slower first layer, otherwise the extrusion just gums up the nozzle. The few PET-G prints he had were either too long (time-wise) or just simple calibration prints.

Sorting out the printer

This is a really neat little printer.

Neat printer

Steph got the knock sensor working using one of my (many) scavenged piezo elements. Yay! He then started setting up some of the ATTINY85s that he bought from me, getting the bootloader onto them using an Arduino as an ISP. He got the first one working by the end of the evening, nice!

ATTINY programming

Jan had some soldering to do. He is building an azimuth/elevation satellite tracker to get satellite coverage in a big chunk of the southern hemisphere for SatNOGS. Awesome project:

Tracker soldering

Cassidy came by and chatted about the maker ecosystem in Stellenbosch, as well as a HUGE (2.4m square build volume) 3D printer he’s been developing for a client. Some interesting problems you pick up at that scale: 6 kW heated bed, getting things straight and squared up over those distances, and making sure that the multi-day prints can be stopped and resumed if needed. Very interesting.

(Also had some interesting sports scoring application, nice project to work on)

I got the drawing machine working again. The whole setup is a bit finicky: It depends on the order in which things are connected and started. I really want this to be a bit more solid.

Clearly obsessed with harmonic motion.

All in all, a very enjoyable evening.

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.