Micro:bit projects

  Solar panel, microbit, battery and regulator Update I have made a few improvements since this post was published in September 2022: The key change is to use a   separate low-dropout regulator (LDO) to provide the 3.3V supply to the microbit and other components. I had previously used the microbit's internal regulator. I found subsequently that it has a curious high-current region as the battery voltage drops, which leads to a period of rapid battery discharge.  AA rechargeable cells, with 1200 mAh capacity, replace the previous AAA 850 mAh cells I use a 2W solar panel and a smaller current limit resistor, so that I can get a higher charging current I added a PNP transistor to the output of the TL431 shunt, so that it can handle more than 100 mA These changes do add a little to the overall cost, but they do give more reliable operation under a wide range of solar input. Introduction This article describes a low-cost DIY solar power source which is aimed at school...

Powering microbits outdoors isn't easy: dry cells have quite a low capacity. Typically a microbit battery of 2 AAA cells can provide around 500 mAh, which might power a weather station for a couple of days. Another solution is a power bank. These are rechargeable batteries that are aimed at the mobile phone market - to keep your phone battery topped up.  They are charged from a mains charger  via a USB input port, and deliver 5V from a second port. The one I'm using is an Apachie 5200 mAh , which is available for around £8. It's the size of a typical phone. Power banks are intended to give your phone 's battery a boost - not to power some electronics which need a continuous supply! So they come with a means of testing if the load has been disconnected; the power bank can then switch off its internal circuits to reduce power wastage. This power bank does that by switching off for a short time (about 500 ms), every 5 seconds or so. That will cause the microbit supply to c...