New electronics for the Raspberry Pi clock

Actually, the clock has been running for quite a while now without any problems. But one small thing still bothers me. For the clock with the acrylic rings I ordered new Hall sensors. Same company and same type. After the installation the software behaved completely different than the old version with the wooden rings. It was even so bad that the Raspberry crashed regularly. After a longer troubleshooting I finally found the cause.

Hallsensoren der Raspberry Pi Uhr und das Schwingen des Hall Sensors

The problem is precisely these new Hall sensors. Even the old Hall sensors tended to oscillate in the limit range when approached with a magnet, but this range was only a few millimeters wide. With the new Hall sensors, this range extends over several centimeters. With the oscilloscope, you can see this behavior very nicely. However, the cause is unknown to me. The layout of the boards is slightly different, but basically the same components are installed. Especially the comparator type LM393 and the hall sensor AH49 is used in both versions. On the internet I found some hints that the LM393 can tend to oscillate, but why this occurs so much more in the new version I can't say.

So I decided to redesign the circuit, but this time with an LM324 type opamp. And while I was at it, I added the control of the stepper motors to the circuit, so that in the end everything sits on one board. I used KiCad, again a program I had to learn from scratch. I had the finished board made by the company Aisler and it was there less than two weeks later. The components were soldered quickly and then the board was ready.

Die Elektronik der Raspberry Pi Uhr

The Hall sensors now sit under a bar. This makes positioning the sensors much easier and the case is additionally stabilized. By the way, the watch looks much tidier now.

Gehäuse mit Elektronik und Hall Sensoren der Raspberry Pi Uhr

Since the bridge also needs a mount, I had to 3D print a new case again. I don't know for how many times. One day later it was ready. So the cyclochron project is finished for the time being. At the moment I don't know anything more I can improve. But I am sure that I will come up with something...

Raspberry Pi Uhr mit Acryl Ringen und neuer Elektronik


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