Building a neat 12v power distribution system.
The Red Tin has had a couple of outings now and has performed well. I have the MIDI controller set up how I like it and I’ve added a bit of wood veneer for the retro feel.
One awkward thing, and a change from my old set up is that I have 3 x 12v adapters to plug in: one for the UDOO x86, one for the monitor and one for the sound card that incorporates a USB hub. Just having one thing to plug in would obviously be a lot more convenient, and as everything was 12v, it should not present too much of a challenge to build a 6-way distribution box, giving me plenty of outputs should I need them.
The bottom drawer of the toolbox was not being used for anything specific, so that would be the obvious place to house it. I talked it over with my colleague and we came up with a plan.
Making it weatherproof
The idea was to have a 12v desktop power supply that would plug into a socket in the back of the tin, that would be connected in turn to a box that would house 6 fused sockets that supply the equipment in the top of the tin.
With my experience of some very wet and muddy music festivals, and with the festival season fast approaching, as well as the wine throwing incident that had sparked the creation of the original Red Tin — see Part 1 for details! — I wanted the system to be as weather and liquid proof as possible.
I started sourcing suitable components — this was my introduction to the world of IP Ratings. The Binder 720 Series connectors, for example, are IP68 which translates as “dust-tight” and “protected against complete continuous submersion in water (up to 1 meter deep for 15 minutes)” — that should do the trick!
I found a nice red aluminium enclosure to house the project that would fit perfectly in the toolbox drawer and set about identifying the other components I would need. Using Inkscape started mapping out where everything was going to fit into it.
- 1 Red Aluminium enclosure
- 1 Binder 720 Series Plug
- 1 Binder 720 Series Socket
- 1 Binder 720 Series Male Dust Cap
- Lapp UNITRONIC LiYY 2 Core YY Control Cable
- 1 Panel Mount SPDT Toggle Switch
- 1 RS Pro 60W Desktop Power Supply, 100 → 240 V ac, 12V dc 5A Output Level V 1 Output, C1
- 6 Binder 620 Series, 3 Pole Panel Mount Subminiature Connector Socket, with Female Contacts, IP67
- 6 Binder 620 Series, 3 Pole Cable Mount Subminiature Connector Plug, with Male Contacts, IP67
- 6 Schurter FPG3 Series 16A Slotted Cap Panel Mount Fuse Holder for 5 x 20mm Fuse, PC2, IP40
- 1 Oxley IP67 Panel Mount LED Indicator, 12 v
- 6 5.5mm barrel 12v plug – red
- 1 RS Pro Blue Crimp Splice
After checking the component data sheets for dimensions I could start working out how things would fit into the box even before they were delivered and using Inkscape started mapping out where everything was going to fit into it.
As soon as the materials were delivered I made a start.
First I needed to make the right size holes in the right places in my red enclosure to accommodate the fuse holders, the sockets, LED and switch. This always makes me nervous – it may just be me, but lining up holes accurately and getting the sizes just right I find particularly challenging. To help with the process I made some templates from MDF using the laser cutter. One set with the holes the size they need to be and one set with just the centres cut out so I could mark the enclosure with a punch to help get the drill bit in the right place.
It went pretty well and the holes all look nicely lined up.
Soldering the connectors, switch and LED
I then fitted the fuse holders and soldered a piece of copper wire to connect them along a common connector.
Each of the free connectors on the fuse holders was then connected to the positive connector on the plugs.
I was then going to run a copper wire rail across the remaining connectors on the plugs but when they were arranged so the mark to line up the plug was at the top, as I wanted so that I could easily get the plugs the right way round in low light conditions, the connections on plugs were not lined up. So I connected them with wire using a crimped connector.
The switch, LED and main input plug were then fitted and wired up.
The filed part on the screw hole in the top right-hand corner of the box is to accommodate the strap of the socket cap.
I replaced the supplied silver screws with some nice black ones to fit in with the look of the tin.
I then needed to fit some fuses and my research revealed the different speed markings:
Very Fast Acting Fuse (Flink Flink)
Fast Acting Fuse (Flink)
Medium Acting Fuse (Mitteltrage)
Slow Acting Fuse (Trage)
I have initially fitted 2A FF but if the Very Fast Acting bit causes problems I will replace them with Medium Acting.
I drilled 3 holes in the front of the bottom drawer of the toolbox to accommodate the LED the socket and the cap. I had decided to put the connector at the front of the toolbox rather than the back as it meant I could plug directly into the box without any internal connecting cables that would not get pulled about whenever I opened the drawer. It also meant it was where I could keep an eye on it and it wouldn’t get pulled out by accident.
I fitted it into the drawer held in place by Velcro so it could be easily removed if necessary.
The Red Tin was ready to go!
The next night I played for about 3 hours in a local bar and it performed without a hitch.
As ever with these projects I have learned a lot along the way — IP ratings and the speed of fuses to name two. The project reminded me of my 9-year-old self-learning from the Ladybird book of Magnets Bulbs and Batteries. I think my 9-year-old self would be pretty impressed.