Back in December I wrote about making a portable anti-collision light systems for, say, cyclists using the Airbus scheme.

That first version used a generic full-size Arduino unit. I’ve been miniaturizing it and changing hardware platforms over the last month or so as parts arrive from China. Here’s version 2 below. It adds the tail light, switches to a LiPo battery and uses a trinket instead of an Arduino:

Version 3 moves to an ATTiny85 programmer board:

Version 4 uses just the the ATTiny84 IC and switches to rechargeable AAA batteries. By rearranging components I removed 8 wires and added an on/off switch:

The next step is to put the thing on some strip board and/or design a PCB and case for it. There are a bunch of mixed considerations as the case and PCB layout interact with each other, and I’d like it to be waterproof for helmet mounting for cyclists. The battery type introduces a lot of complexity – a rechargeable lithium cell is probably best but that means integrating the charging cicuitry and having a USB socket on the thing. I have more parts ordered from China to test all of this.