I made several wrist holders for the microbit and a AAA battery pack as I could not find a suitable off the shelf solution.
Since I made my own - instructions below, I found a couple of ready-made solutions that I write about in this blog:
Make your own microbit wrist holder
This section shows you how to convert a £3 iPod 7 armband into a wrist or arm holder for a BBC micro:bit board and battery. The photo shows the first one that I built being modelled by the local electronic's wear supermodel. I have made a few of these now and each time I make a few improvements.
I have a project which requires a micro:bit and battery pack to be securely worn on a wrist or arm. More details of this project are at https://mattoppenheim.com/handshake
I start with a 'King of Flash New iPod Nano 7th Generation Premium Water Resistant Armband Case' from eBay for the princely sum of £3.
Remove the plastic iPod holder bit with a few minutes of cutting with a suitably sharp instrument. Leave the cover over the slots for the strap. For the first couple of holders that I made, I removed the top cover completely and then sewed one of the plastic reinforcements back on. Leaving the cover over this bit saves an hour's work. Please see the photo below.
I sew up the slot in the neoprene at the bottom of the photo and add some elastic loops to hold the battery pack.
I use a AAA battery holder with a switch on it that I also bought from eBay for about £2 instead of the 'always on' battery pack that came with the micro:bit. This means that I need larger loops than are required for the smaller battery case that comes with the micro:bit.
As most of the mass is in the batteries, I use 10mm wide elastic for these loops. I cut 90mm lengths of the elastic and sew it into loops with a 20mm overlap of each end of elastic. Sew them onto the wrist holder about 30mm apart as shown below.
Top tip: check that your loops are the right size before sewing them onto the wrist holder by putting them onto the battery pack.
Then add loops to hold the microbit board. The microbit board is light compared with the battery pack, so 3mm elastic cord is ample. I cut 115mm lengths of cord and sew them into two loops, each with an overlap of 25mm of elastic. I sew the loops 30mm apart onto the wrist holder. The photo below shows one loop in place, with the second ready to sew on.
Top tip: check that your loops are the right size before sewing them onto the wrist holder by putting them on the microbit.
The fully assembled wrist holder can be seen below.
To help get the strap to stick to itself and close the holder, I use some sticky back velcro of the 'hook' gender. I stick two pieces back to back to form a velcro 'gender-bender'. This sticks to the belt part of the velcro on the holder, next to where the board and battery will sit.
The assembled wrist holder with the micro:bit and battery pack is shown below. The gender-bender velcro is indicated by the yellow square.
If you are worried about the battery pack flying off after a violent wrist motion, you can double secure it with some sticky back velcro between the back of the battery pack and the neoprene of the wrist mount.
A friend pointed out that the holder could be used to strap the microbit on the leg or upper arm, not just the wrist. For instance, you could log accelerometer and temperature data during sports, using a second micro:bit connected to a laptop to wirelessly log the data from the micro:bit attached to your body. Or log the data to the microbit's memory and recover it later.
There you have it. How to make your own micro:bit and battery pack wrist/arm/leg holder.
Off the shelf Classic iPod holder solution
Having made a couple of my own wrist holders I am the first to admit that this is time-consuming. I tried several off the shelf phone arm holders. None of them seemed comfortable enough to ask somebody to wear them for while.
Finally, I tried a Classic iPod holder made by igadgitz that may be suitable. I have yet to try it with the target user group though.
Please see a front view of the holder below. I added some of the double-sided velcro gender-bender strips to the velcro already on the holder. This helps the holder close when worn on the wrist, which is thinner than the upper arm that the case is designed to go around.
Please see a photo of the back below. There is a flap over the back of the holder. This is thicker and more comfortable than the backs of other telephone and iPod holders I trialled. This flap pulls down to insert the micro:bit and battery pack and holds in place with velcro. Overall, it has a better standard of construction than the other pre-made holders I have tested.
I think that my home-made wrist holder looks better and is lighter than the store-bought one. But expecting busy people to spend 2-3 hours to make their own holder is unrealistic. If this off the shelf solution is good enough and the end-users find it comfortable, this is the way to go.