Gemma projects revisited
2025-Mar-26, Wednesday 12:00 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
chebeIt can be funny, what projects end up being used for a very long time. But with time comes maintenance, and possibly even improvements. Which is what happened as I was considering ways to make my beloved Gemma projects less fragile. When they were constructed I didn't have a 3d-printer, which ruled out experimentation. But I do now.
I found Adafruit has provided the Gemma M0 Case model, which is a lovely slim snap-together case that leaves the USB-port accessible, and has a small hole either side for cable access to the pins, and two stands internally (for screwing down the board if you want), with just enough space for the (hard to find) tiny 100mAh lipo battery. I started iterating on variations. First I took the switch cover out, as most of my Gemmas are actually the original version that doesn't have a switch. (If I find need for it I can always just print another lid.) Then I added an additional four extra holes for easier access to all the pins. And this becomes a lovely self-contained component for slipping into discrete pockets.
But power requirements vary widely depending on the project. Take my LED wire Shamrock sign. This has proven to be mostly used at indoor events, where it is taped to the top of a long pole, and plugged into mains. It doesn't need to hold a battery. But it does need to contain a potentiometer-upon-protoboard. For this version I removed the internal stands, and removed a 16mm circle from the case base. It fits perfectly.
But even when batteries are required, I've found myself less comfortable wearing lithium-ion batteries right on my skin. So when it came to my NeoPixel Tiara I opted to switch to coin cell batteries. This holder takes two CR2032s, and includes a power switch. It's a lovely package. And after soldering a JST PH connector cable on to the ends I can plug it directly in to the Gemmas JST connector. (The original Gemmas can take up to 16V DC, so I can even use rechargeable 2032s without worry.) And the length of the battery cable means it reaches down to my shoulders, where it is much easier to switch on and off.
Unfortunately the 3d-printed part of the tiara is not holding up well. It was never a great print, the hair teeth snapped off almost instantly. The strands of the layers have also continued to separate, and in a desperate ploy to prevent it disintegrating completely I have wrapped it with ribbon. (Yes, all black would have looked better, but we use what we have.) Basically, in sections, with the ribbon ends melted to finish, and using hot-glue to attach, I wrapped the ribbon around the whole band. Leaving a gap for the switch.
To cover the Gemma I actually used an older iteration of the M0 case I had, that only has extra port access on one side. And seeing as how I need the JST connector towards the opening (instead of the USB port), I just put it on upside down. There is a piece of foam under the board to pad out the extra space, and to fill up the hole intended for the JST connector. It's working well enough as is, but I can always print a new version if needed.
(With the hair teeth gone, I keep the tiara on my head with two shop-bought grips that just fit around the band. Not with supernatural balancing abilities. If you were curious.)
But if we're talking about improvements around things involving Gemmas, then I'd like to present a lifetime achievement award to the maker of this JST connector extractor model. It's explicitly for micro:bits, but it's the same JST-PH form factor as used by Gemmas, Floras, and Lilypads. It is the 20 minute print that I wished I've had for the last 15 years. *applause*
I found Adafruit has provided the Gemma M0 Case model, which is a lovely slim snap-together case that leaves the USB-port accessible, and has a small hole either side for cable access to the pins, and two stands internally (for screwing down the board if you want), with just enough space for the (hard to find) tiny 100mAh lipo battery. I started iterating on variations. First I took the switch cover out, as most of my Gemmas are actually the original version that doesn't have a switch. (If I find need for it I can always just print another lid.) Then I added an additional four extra holes for easier access to all the pins. And this becomes a lovely self-contained component for slipping into discrete pockets.
Gemma M0 case, top, with extra pin access, and no button
Photo by chebe
But power requirements vary widely depending on the project. Take my LED wire Shamrock sign. This has proven to be mostly used at indoor events, where it is taped to the top of a long pole, and plugged into mains. It doesn't need to hold a battery. But it does need to contain a potentiometer-upon-protoboard. For this version I removed the internal stands, and removed a 16mm circle from the case base. It fits perfectly.
Gemma case lid, now the bottom
Photo by chebe
Gemma case base, now top, with circle removed for the potentiometer
Photo by chebe
But even when batteries are required, I've found myself less comfortable wearing lithium-ion batteries right on my skin. So when it came to my NeoPixel Tiara I opted to switch to coin cell batteries. This holder takes two CR2032s, and includes a power switch. It's a lovely package. And after soldering a JST PH connector cable on to the ends I can plug it directly in to the Gemmas JST connector. (The original Gemmas can take up to 16V DC, so I can even use rechargeable 2032s without worry.) And the length of the battery cable means it reaches down to my shoulders, where it is much easier to switch on and off.
Unfortunately the 3d-printed part of the tiara is not holding up well. It was never a great print, the hair teeth snapped off almost instantly. The strands of the layers have also continued to separate, and in a desperate ploy to prevent it disintegrating completely I have wrapped it with ribbon. (Yes, all black would have looked better, but we use what we have.) Basically, in sections, with the ribbon ends melted to finish, and using hot-glue to attach, I wrapped the ribbon around the whole band. Leaving a gap for the switch.
To cover the Gemma I actually used an older iteration of the M0 case I had, that only has extra port access on one side. And seeing as how I need the JST connector towards the opening (instead of the USB port), I just put it on upside down. There is a piece of foam under the board to pad out the extra space, and to fill up the hole intended for the JST connector. It's working well enough as is, but I can always print a new version if needed.
(With the hair teeth gone, I keep the tiara on my head with two shop-bought grips that just fit around the band. Not with supernatural balancing abilities. If you were curious.)
Gemma case base, now top
Photo by chebe
Overhead shot of the improved tiara, complete with battery case and hair grips
Photo by chebe
Tiara in operation
Photo by chebe
But if we're talking about improvements around things involving Gemmas, then I'd like to present a lifetime achievement award to the maker of this JST connector extractor model. It's explicitly for micro:bits, but it's the same JST-PH form factor as used by Gemmas, Floras, and Lilypads. It is the 20 minute print that I wished I've had for the last 15 years. *applause*
JST-PH extractor tool
Photo by chebe
