Bottle light update

I’ve been working on variations of the Joule-Thief -based bottle lights I’ve been making. I made a couple using strip board for the through-hole components but its clunky. Better yet would be SMD components stuck directly onto the structure…

Joule Thief circuit using tape to adhere SMD compnentsJoule Thief circuit using tape to adhere SMD compnents

Some time back I adopted a simple technique I saw where you use sticky tape to put SMD components across copper tape “traces”. This was my first go at a slightly-less trivial circuit and not surprisingly it failed. I’ve not really diagnosed exactly where the problem was yet. It could be I got something in backwards, but more likely its one or more bad connections. I used some tape I had bought that is normally used for repairing polytubes and greenhouses. The idea is that its UV-stable and semi-permanent - regular scotch tape or sellotape becomes brittle over time and would fail. But this stuff is quite thick and and doesn’t grab so much (less sticky) so even as I was putting it together I was concerned it wouldn’t hold down those components well enough to make a reliable electrical connection.

I could just glue the components down, but with the capiliary action there’s a good chance the glue would get in between the component contacts and the tape. So better still would be a conductive adhesive. The good ones (silver particles in a silicon or expoy base) however are spendy so that’ll need to wait while I save my pennies. Backing up a little, of course the strongest and most reliable solution would be to solder the joints. I’m trying to avoid that for a couple of reasons: first because any heat-based process risks distorting and melting the substrate - which is currently PET (Polyethylene terephthalate) plastic. The second reason is a bit more fluffy - I just want to find other ways to assemble these circuits that are maybe more kid-friendly, or less intimidating or don’t require special tools. That might yet turn out to be an unreasonable and impractical requirement but I’m not done yet.