Update: Thanks for the overwhelming response to this! I’m currently working on the design of this shield with input from several community members and plan to have the shield produced by Spark and sold on the Spark Store. Be sure to read through the thread to see how the design has unfolded and check the latest posts at the end of the thread for current information!
I don’t like mustache board too.
I like your one and would like to suggest one more thing - optional switch, enabling powering spark.
Battery status by i2c is great addon
I see, so a switch to turn the Core on and off when on battery power? Since the Core is sitting up a bit on those female headers, I could place a little horizontal switch where the solid white box is in the first image. Would that be alright?
Very very interesting!!!
Great design. I would definitely purchase one!
+1 (or + a couple actually) for me.
Would it be possible to add trickle charge from something like a solar panel? I know Adafruit have something similar.
I have some old Panasonic cells hanging around and would love to be able to get a top up if the sun shows its face.
I’m in. I’ll take 2.
Expanding on my idea of adding an I2C based GPIO Expander, I modified the form factor a bit, making it thinner (0.9" wide down from 1.1") by removing the outer row of 0.1" holes. I added an SX1509 16-Port GPIO Expander Chip which routes to two 2x8 0.1" headers (under the Core) on the front and back of the board. This would add 16 extra
analogWrite channels to the Core, with hardware interrupts, hardware PWM (for LEDs etc.) and hardware switch/button/keypad scanning.
So the Core would plug into the Battery Shield which itself would plug directly into a breadboard (and all the Core’s pins would route straight through). The GPIO expansion would be accessible from the right-angle headers on the shield under the Core.
This is just an experimental direction I could take the board in if you guys think it would be useful. If there’s no interest I’ll drop the GPIO Expansion and continue down the original path, no harm no foul. (I like to practice experimental, iterative design. Doing it for the community will be fun!)
Yes, actually! At least one of the charging solutions I’m testing supports alternate energy inputs: Solar, Thermal and Piezo. This may require external circuitry you’ll need to provide (a large capacitor in the case of solar). Depending on what other on-board components are needed, I may also add the footprints and just let the end user hand solder those parts if they so desire. At any rate solar would be very nice to have for outdoor environmental monitoring projects, so it’s on my list!
I’d be interested, as anything is better than the abomination.
How many depends upon cost. I’d probably be interested in a couple, though.
Being able to charge directly from solar would be nice, but certainly not essential. The solar panels I’ve seen output ~6V.
Maybe it’s just me, but I’d like to see a ground connection on each GPIO header (even if you have to drop one of the GPIO lines), and maybe a filtered 3.3V, too.
timb, as being one of the first to voice my incredible dislike for that “whimsical” POS mustache things, I would absolutely take one of your shields. I am not so crazy about the horizontal headers on either ends of the board but I can’t think of a better way to expand I/O. +1 for the solar cell charging.
Can I ask why the battery connector has 4 pins as most I have seen are all 2-pin JST connectors?
Oh yeah, I couldn’t find the JST connector in my 3D library right away, so I just used that as a placeholder. I think that’s one gof those stereo CDROM drive connectors, the kind you had to run from your drive to sound card back in the day!
Don’t worry, a real JST plug will be in the finished product!
My requirements are relatively simple i2C, Fuel gauge, Battery.
I like the idea of an LED bar graph show the status externally but I think I’d like this exposed as a separate unit that could be mounted appropriately in a case.
I’m also interested in this. A fuel gauge would be great as well.
What I really would like (but know will not be likely to get) Is 2S or 3S support. This will allow for the core to be powered off the same circuit as the servos. The fuel gauge would then be amazing!
I’m starting to see the benefit of DipTrace over Eagle Love the 3D models. Personally I’m an OrCad guy, and like KiCad because it’s more like OrCad than Eagle… but pretty much all open source hardware people rally around Eagle so I’ve had to learn it as well.
It’s about time someone proposed a new LiPo charging backpack!
I would say add whatever you want for “playground” parts, as long as they can be completely isolated in case a user doesn’t want something hooked up to various I/O. The fuel gauge sounds like a done deal. Pull up resistors, check.
What I would love to see is a low voltage cut off on the input of your buck/boost circuit, perhaps programmable with one resistor. Maybe even bridging a solder short could change it from 3.0V to 2.8V or 2.6V. Not sure how safe people want to be with their batteries.
It would be nice if there was room somewhere under the Core, but above the Lipo backpack for a known certain size Lipo. Obviously you may want to just power it with a large lipo that’s obviously not going to play. Obviously you can’t change this inner volume much so I guess this is just a research part.
A way to “latch” the battery management circuitry into low power mode (shutdown), would be nice. See my post here about low power ideas: (probably not easy to work this in … but… if there was a 5V/3.3V mode to your buck/boost, you could power the Core directly on the 3V3 pin and the Core’s on-board 5V LDO wouldn’t waste so much power when you put the core to sleep).
You can definitely put me down for at least 1, if not 2 of these
I would certainly be interested. An on/off stitch would be virtually mandatory for battery powered operation, I think. With the mustache you can cut the output usb cable and run it to/from an externally mounted switch, so a nice external on/off switch capability (maybe another JST plug?) would be nice
I like the idea a lot, for me, I’d sacrifice some of the additional gpio’s for the switch, the switch is essential!
Especially one that you could come up with a way to actuate once you package the whole lot in an enclosure, so perhaps a slide switch…
Also a status led for charging, yellow charging, green fully charged?
charge status light
my 2 cents
There is too little space there. I’ve already scanned internets for LiPo sizes. Most suitable are from RC Helicopters (V911 one for example fits between arduino nano pins) but max size would be around 130-150Mah 3.7V
Hey guys! I wanted to provide some input from the Spark team in response to this awesome thread. Firstly, we continue to be impressed by the ability and enthusiasm of this community. We think it’s great that there’s interest in community-led development for new Spark accessories, and we’d love to work with you guys to create a manufacturing pathway for these creations so that everyone can benefit from them.
Basically, our idea is to offer up our manufacturing supply chain to help bring the most popular shields and accessories to the rest of the Spark community. We’d work with the project’s leader(s) to bring the designs through validation/sourcing/manufacturing/testing/packaging, and aim to minimize costs all around by leveraging an active supply chain. Finally, we would work with the project creator(s) to figure out a distributor agreement so that we could sell community-led accessories alongside Spark-developed ones, as one big happy Spark family.
We’re continuously impressed by the projects you all share, and would love to test-drive a mechanism for realizing the best of those community-led contributions on a much broader scale. It looks like there’s significant interest in an alternate battery shield, and we think it’d be a great opportunity to pilot a process that we could open up on a case-by-case basis to other shields and accessories in the future.
What do you guys think?