chris – ettis.at

2023-01-07

QR-Code für WLAN erzeugen

Ein QR-Code ist eine komfortable Methode, Informationen in ein Handy zu übertragen ohne sie manuell eingeben zu müssen. Das können Web-URLs, E-Mail-Adressen oder auch ganze Visitenkarten sein. Einfach mit dem Handy abfotografieren, drauftippen und schon hat man’s.

Das funktioniert auch mit WLAN-Zugangsdaten! Heutzutage drucken viele Restaurants die SSID (=der „Name“ des WLANs) und das Passwort auf die Rechnung. Hotels reichen dem Gast einen zusätzlichen Zettel, Firmen legen laminierte Flyer in Besprechungsräume oder hängen die Zugangsdaten an die Wand. Dabei wäre ein einfacher QR-Code zusammen mit einem sprechenden Symbol viel eleganter!

Für mein Gästenetz zuhause wollte ich genau so einen QR-Code erstellen. In diesem Beitrag möchte ich beschreiben wie ich das geschafft habe.

2020-10-09

How to increase my Synology NAS backup storage

I recently ran into the problem that the backup storage of my Synology NAS ran out of space. Buying a bigger harddrive is trivial – keeping all existing backup data and continuing incremental backups is not. I googled a lot because I thought this is a fairly common problem, but strangely I couldn’t find any guides on that. So, I did a little bit of trying and hacking and in the end, the solution was simpler than I expected. In this post, I want to show you how I did it.

2019-11-262020-01-06

Bowl Feeder: First Prototype!

Good news! The first prototype of my bowl feeder is ready! Finally I can do some tests and see how the mechanics are working!

It was an exciting moment to switch on the vibration for the first time, and to slowly increase the amplitude and try different frequencies. Unfortunately, the result was slightly disappointing: nothing happened.

2019-11-132019-11-17

Bowl Feeder Control Circuit

The bowl feeder needs to vibrate with just the right frequency and amplitude in order to move the beads the optimal way. Since I don’t know the optimal parameters yet, I want to make a control circuit that allows me to tune frequency and amplitude of the vibration. In more technical terms this means I need two control knobs, two displays and a microcontroller for generating a PWM signal.

2019-09-192019-10-20

3D Printing

Now that I have finished designing the bowl feeder, it’s the time to get it 3d-printed. I never intended to 3d-print it myself, this would be similar to making printed-circuit boards (PCBs) myself: It would be a huge project of its own and there are companies out there, who offer professional quality at a very good price. But still, one has to understand the challenges of 3d-printing in order to avoid common pitfalls in designing the model.

So I searched the Internet for a suitable printing-service provider. I found https://all3dp.com/, who submit your model to different providers and show you the providers with the best price vs. the shortest delivery time. Both parts, the bowl and the base cost me less than 20€ each incl. shipping and VAT.

2019-09-082019-11-09

Learn professional CAD software

A bowl feeder consists of more than just the bowl: It needs a stand and, most importantly, some kind of suspension to allow it to vibrate as needed. When planning the next steps, I quickly realized TinkerCAD will not be the best tool to support me with these things. When I discussed my project with a professional, he recommended Autodesk Fusion 360. He also pointed out there is a free license for hobbyists and start-ups (thanks Florian!). Since one of the goals of this project is to learn new technologies, I thought I should learn them with the proper software. So that’s why I decided to work into Fusion 360.

2019-07-202019-11-09

Programming a spiral

As I wrote in my previous post, I decided to program a Custom Shape Generator in Tinkercad in order to be able to generate every detail of my bowl feeder just as I want it to be. I spent my two weeks summer vacation in Italy thinking about sine and cosine, vectors and loops. I implemented the JavaScript code on my cellphone, although characters such as the square brackets [] were a challenge and I needed to install a special Android keyboard app for these. When coming back from Italy it was almost finished, only a few minor details needed to be fixed.

2019-07-042019-11-09

Designing a Bowl Feeder

Bowl Feeders are used very often in industry when a bulk load of pieces must be separated into single pieces. They consist of a bowl with a spiral ramp on the inside. The bowl is vibrated around its center in a way that each point of the ramp vibrates horizontally and vertically, e.g. in a small circle. This will cause parts on the ramp to be thrown forward a little on each vibration.

Each bowl feeder must be made specifically for the goods it should process, mainly for the pieces’ physical dimensions. This is the reason why I want to 3d-print my bowl. 3d-printing is quick and if a tiny detail doesn’t fit, I can cheaply make a new one.

2019-06-192019-11-09

A new project idea!

As chance would have it, I find myself with a lot of spare time over the summer. This screams for a new project! Recently, I have made a list of skills I already possess and skills I would like to learn. So the project that I choose should help me learn a few of these.

After a lot of thinking I came up with the following: I want to make a machine that sorts my perler beads for me!

2018-09-062018-09-07

Predicting periodic events with FFT

Problem description

We have embedded devices periodically sending us data. We want to be alerted as early as possible when a device stops sending data.

A very simple approach is to take the time difference of the last few times a device sent data and calculate the average. When we know a device sends data roughly every 15 minutes, we can easily trigger an alarm if no data arrived for that time.

The above approach assumes devices send data with the same period always. However, that is unfortunately not true for all. We have found devices which never send data during the night. Or devices which stop sending every afternoon, presumably because their GSM internet connection becomes disturbed. Continue reading “Predicting periodic events with FFT”