Here’s the TL/DR version of this blogpost: if you are using the BBC micro:bit, especially with children, make sure they heed the advice on these panels in the middle of the back of the ‘Getting Started’ leaflet. In effect this means you can’t easily use the micro:bit buttons when it’s plugged in to a computer, as the natural way of holding it is to put a finger behind the A button to support it as you push:
Still interested? Here’s the background.
I’ve had 3 preview teacher micro:bits for a few months, and they all worked swimmingly… until I started using them with children. One unit got warm but still worked, another got incredibly hot (dangerously so) and failed. I sent it back to the BBC and got a replacement unit, which worked fine again – until I started using them with children. The new unit also started getting warm, but it still worked.
The BBC told me the chances of having multiple failures were ‘billions’ to one, so there must be an environmental factor. They sent me 5 more micro:bits to test in the same ICT room, on the same computers: HP Chromebooks. I spent about an hour testing them – and they were all perfectly fine. Must have been a fluke. A billion-to-one fluke.
Then I tried them out with my Year 5 computer club – and 2 of the new 5 micro:bits also now started getting warm. Not dangerously so, but noticeably warmer than normal.
Logically the only explanation for the mystery of the micro:bits was: children. I toyed with the idea of positing a new particle called a childon. Children must emit childons which have the effect of frying integrated circuits.
It turns out that my experience with the micro:bit is reproducable, and is, I am told, caused by 3 things happening at the same time:
- The micro:bit must be plugged into a USB socket that can deliver enough current to charge a phone
- The user must be touching the metal test pads on the back of the device
- The user must cause an electrostatic charge to go into the device
Now this is a bit of a problem, because I think these 3 things will happen really quite often indeed. Firstly, most children test code, upload it, tweak it, upload it again. Combine that with the need for batteries, I think most micro:bits will be plugged into computers most of the time. Our HP Chromebooks are not unusual devices in schools, they have USB 3 sockets, and apparently these provide enough current to be a problem.
Secondly, it’s hard to avoid touching the test points on the back, especially as the ones in question are immediately behind the A button. It’s natural to hold it there as you push the button. Is it reasonable to expect children always to remember to hold them by the edges?
Thirdly, electrostatic shocks. My problems were in a room where I’d never noticed static shocks, but the floor is covered in carpet tiles, presumably nylon, so it’s a possibility. In my main ICT room I get shocks all the time, so when we use the class sets with Year 7 we will all have to keep earthing ourselves on something – not quite sure what. Do I need to run an earth to every desk?
I write all this with a heavy heart. I like the device, I love the microPython on it, I’ve written Python games for it, I’ve re-made the ‘happy plant‘ physical computing project, I’ve planned lessons for it.
But I fear that unless teachers and children read the leaflet carefully and heed the advice, an awful lot of micro:bits will fail, some may even get dangerously hot – though I should stress only 1 out of 9 initial units felt hot enough to burn, but a high proportion of the micro:bits I’ve actually allowed children to use run warmer than they should and draw more current than they should. I do wonder what would happen to the warm units if left plugged in for a long time – there is another warning panel about not leaving them unattended and unventilated on the back of the Getting Started leaflet. Where do I stand legally, as a teacher, if I give a child a micro:bit to take home and at home it causes an injury or fire?
The project is already beleaguered by insane delays – we were supposed to get them near the start of the academic year. That was 2015. We finally got our class sets for Year 7 last week, but because of upcoming exams and school trips, I now can’t use them until after half term in the Summer 2016 term. It’s a one-off giveaway, so the current Year 7s will only get a few weeks’ use out of them – and then we may struggle to use them in class. “Right Year 7! Only hold them by the edges! Earth yourself! Don’t use them when they are plugged in to the computer!” I may be an exceptionally poor teacher, but I find children do not always hear, understand and follow instructions in class. And the supplied USB leads are so short, usage will anyway be quite comical given our PC base units are built into the bottom of the desks.
It all just seems like a tragic mess, a wasted opportunity. I wish the BBC had been able to say “we messed up, let’s hold it over a year and you can hand them out next year’s Year 7s, or Year 8s if you already told them they were coming.”
Luckily I have still not told my current Year 7s about the micro:bit. And I am still not sure what to do with them.
How not to handle a micro:bit: