Measuring in at a minuscule 4cm x 1.9cm (1.6 x 0.75 inches), it still packs nearly the same punch as the original -- with some additional features!
To open up more possibilities with data logging and larger CircuitPython programs, it now rocks an onboard 16MB SPI flash chip.
There's an additional tiny RGB Dotstar LED (APA102-2020) for more LED indicator options.
The power indicator LED is now inside the power button. When the board is turned on, the button is illuminated. There's also a cuttable trace to disable or rewire it if needed.
What's the catch?
Of course, I couldn't shrink it this much without losing something.
The battery is no longer is embedded on the board. However, there's a standard JST battery connector and it still has the 500mA lithium battery charger. I found that bundling the battery on the board limited its applications in some areas. I still prefer cylindrical batteries for wearable applications and have been playing with JST connectors and shrink tubing to repackage some batteries.
To conserve more space, I had to reduce the PWM MOSFETs from 2.3A to 1.4A.
It was really hard keeping the four PWM LED indicators. On a 2-layer board this tight, finding room became difficult. I almost had to ditch them entirely, but at the last minute, I was able to find some room on the other side of the board.
Besides that, and outside of a few new circuit design choices, that's pretty much all it lost. The new board does nearly everything the original did, with some new features, at a fraction of the size.
What do you think?
After a few more checks, I'll be making a new production run to sell on my tindie store. I'm debating if I should keep both the original ThunderPack form factor (with the added new features) along with the new compact version, or fully commit to the compact version and deprecate the old. What do you think?