Mastodawn

Kit Bashir Jul 18, 2025

#HackOfTheDay is free-form circuit remixing. I’m installing some Meshtastic devices which use LoRa radio (low power long range wireless). I want to use solar power but need to know how much energy I use. To do this i’ll install an electric current sensor between the battery and the device. But this device has the battery soldered directly to the circuit board, I need to get creative. 🧵

Removing the battery holder leaves me with two points to connect my sensor, the pad on the PCB and the battery holder. But I’d like to retain the firm attachment of the battery holder. My current sensor has two through-holes for these connections, but it doesn’t have pads on opposite sides, then i could just insert it into the gap. BUT: sufficiently advanced bodging is indistinguishable from planning!

Kit Bashir Jul 18, 2025

Polyimide is a plastic that is heat resistant. “Kapton” is a kleenexesque brand name that you’ll probably recognize. In adhesive tape form you might have seen this orange material surrounding lithium polymer batteries in phones and drones. What I’m going to do is cover both sides of my sensor with Kapton and then cut away two areas on top and bottom, in order to effectively get a “top pad” and “bottom pad” on my sensor.

Kit Bashir Jul 18, 2025

With my sensor now converted to a “wedge” I can insert it between battery and device. But did I make a short circuit? It’s hard to be sure because there is a very low resistance component between the two pads, so using a normal continuity tester is not probitive. So I hot air desolder the shunt resistor and confirm that, yes, everything connects the way it should, with no shorts.

Kit Bashir Jul 18, 2025

Another tool of the Bodger’s Art is wire-wrapping. Very thin insulated wire and a special tool are used to make temporary but strong connections between pins. You will find computers in museums from the 1950s and 60s made this way.

Kit Bashir Jul 18, 2025

You might have noticed that red wire went to the wrong pin. Another advantage of wire wrap is the ability to un-do it.

Briala Jul 18, 2025

@Unixbigot I still remember when Tandy sold wire-wrapping tools. I never learnt wire-wrapping, though.

LovesTha🥧Jul 18, 2025

@Unixbigot You'll also find them on the moon right...

JonnyB Jul 18, 2025

@Unixbigot I still have the tools and even some short wire strips, with pre-cut insulation, from my mainframe days! I had not thought about using it as a temporary or even permanent connection in projects though!

JonnyB Jul 18, 2025

@Unixbigot and I was working on mainframes up to the mid 90s that used wire wrapped backplanes.

Robin Frousheger Jul 18, 2025

@Unixbigot most of the aus telephone exchange linkages are/were wire wrapped before the new-fangled krone ‘punch-down’ blocks became common.

most of my late 80s hackery/kits were wire wrapped and/or veroboard.

i wire wrapped a whole custom 6502 computer for an assignment in the early 90s (all the rage, 30 years later 🤣)

i still have 100m+ or various wire, and a tool to do so .. somewhere

Mike Jul 18, 2025

@Unixbigot You'll also find telephone exchanges from the 1970's making extensive use of it in the UK.

Robin Frousheger Jul 18, 2025

@Unixbigot masterful ❤️

Anthony Horton Jul 18, 2025

@Unixbigot You know someone means business when the Kapton tape comes out!

Scientific instruments and satellites are full of the stuff, because it's vacuum compatible in addition to being heat resistant.

Kit Bashir Jul 18, 2025

@spacelizard good to know! I do occasionally reach a stage on some projects when I want to fire the hardware into the sun.

Anthony Horton Jul 18, 2025

@Unixbigot Here's a photo of the inside of the Curiosity Mars rover. Plenty of little rectangles of distinctively bronze coloured space-tape in there.

Kanerva Jul 18, 2025

@spacelizard @Unixbigot Why can't they put better glue on it 😩 I use Kapton tape at work (for thermal testing where temperatures can be too high for most tapes) and getting it to stay put is a pain.

But knowing that I'm working with space tape makes it worth it!