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Progress is still slow whilst I wait for more bits and pieces to arrive.

I’ve ordered an HP EliteDesk Mini to try out as a “pier-top” machine and weatherproof boxes for each pier which will contain most of the electrical stuff on each.

Weatherproof ABS boxes are relatively easy to find as long as you want solid doors, but because it’s sometimes reassuring to be able to see inside I was looking for ones with clear doors. The only source I found for boxes a convenient size for my pier was on Ebay. They’ve not arrived yet however.

I’ve also been running cabling from each pier to the warm room. I have three runs of 2.5mm “twin and earth” to each pier, the thinking being that I can either use two runs for the 12V supply and the other for a 240V spur, or the other way around with a 240V ring. The cable should be ok for up to 25A and I really can’t imagine I’ll be needing that for either.

Some data cables are also in place, too. From the two mounts furthest from the warm room I’ve pulled through a 5m HDMI cable, followed by a 5m USB2 cable, and then two lengths of cat5e (somewhat longer, to allow me to decide where the hub is going to go later). I’ve not done the last pier yet because I’ve been waiting for a shorter HDMI cable to arrive and I’m pulling them through in order of size of the plugs in the hope that will be the easiest way to do it. That last cable has in fact now arrived, but the weather has been so unpleasant here over the last twenty-four hours that I’ve not felt like going out and finishing off.

So it comes to that time when I need to think about power. In particular 12V (or 13.8V) power to the piers to supply most of the kit that will be on them.

Initially my thoughts were to have a single PSU in the warm room to provide power everywhere, but I wasn’t really happy with a single PSU failure hitting all the mounts. That meant having multiple PSUs either in the warm room or at the pier, but multiple PSUs also seems a bit wasteful (and consumes a lot of space) and if they were on the pier then ensuring they were adequately ventilated whilst keeping the dew away from them was going to be a challenge.

Then someone suggested to me that I could use a battery wired in parallel with a PSU with fuses each side of the battery to protect everything and switches to allow circuits to be disconnected. It’s not a cheap solution, but it does mean the battery could power everything, possibly for several hours, in the event that the PSU died. I’d need to turn down the voltage a little, perhaps to 13.5V or 13.6V, but that should be fine.

An alternative suggestion was to just get two lower-rated PSUs and power some stuff from one and some from the other. That would probably cost the same as the single PSU solution without the battery.

So for the time being I’m dithering a little. I do need to make a decision very soon though.

Another decision that I think I’ve settled is cabling for the 12V supply. I’m fairly sure now that for the runs from the PSU to the pier I’ll use 2.5mm “twin and earth” as used for mains house wiring (and I have quite a bit lying about). A single run through the ducting should be good to carry perhaps as much as 25A, which should be more than I ever expect to need. At the pier I can split it into multicore cables to feed the mount and other kit. The alternative would seem to be to use a couple of runs of multicore automotive cable capable of carrying around 11A and balance the load across each, which seems a bit more awkward really.

So, need to get that power supply decision made…