Managed A/B switch

This project is by me (Gareth Coleman) and my friend John Cahill - he's doing the clever software bit, I'm doing the easy electronics bit. Basically it's a computer controlled set of relays that directly connect one common RJ45 socket to one of two other sockets. The main use case is that you have your ISDN connection with up to 32 phone lines on it - going to a VOIP server - when that server breaks you want to be able to switch the ISDN lines over to the backup server without having to go down to the comms room to do it. So the hardware basically switches the incoming ISDN onto either one of the main socket A or the backup socket B.

We're using a raspberry pi because they are both cheap and popular; we can use familiar tools to develop software on it, we can also run cluster-aware management services on it easily.

We're hoping to do some front panel work and perhaps also make the pcb here in refab space, once we get to know the people and systems a bit better.

Update - 12th June 2013

Last week I worked hard to finish the front and rear panels, and in the end I was really pleased with the results. I decided to call our collaboration layer zero labs - the name only being chosen as I was laying out the final design for the front panel. I did a quick search to check that the domains were available and no other similar projects/products used the name.

Another idea that occurred to me whilst finishing the front panel was to cut out the OSHW logo - and now it's begging to have an LED fitted. However, I'd like the light to be a hardware indication of power applied but also be able to be controlled, not sure how I'll go about that yet…

I'll post some more photos and write some more text soon, and the full designs will be published here in glorious compliance with the OSHW just as soon as I can find out how to attach them! In the meantime I can add the front panel design as a picture:

I often have trouble finishing projects , partly because improvements occur to me all the time. So the next revision of the project will include the following improvements:

* Two raspberry pi's to provide redundant control

* Two 240v power supplies - one for each pi, again for redundancy

* Encapsulated power supplies so that I can display the project without endless comments about the danger of the power supply!!

* Each pi will control one coil in each relay, with separate driver circuits

* Front panel power indicator (instead of rear) possibly with status indicators?

* Front panel switch indicator LED's controlled by hardware instead of software

Update - 13th June 2013

I can't find any of the schematic files apart from one that has corruption, so I'll have to re-draw the circuit. Bugger. How many times have I told other people to take backups!! At least it will give me a chance to compare gEDA with KiCAD with Fritzing, and I need to change the circuit anyway.

Update - 28th June 2013

Inevitably I got distracted making edge-lit signs and so haven't got very much farther with re-drawing the schematic.

But now I can return and announce that I've looked over the main open-source solutions and I can eliminate gEDA as it seems less actively developed recently.

KiCAD has a lot of momentum at the moment and Fritzing looks super easy to jump in, but I think that KiCAD has more momentum behind it.

I'm hoping to be able to send my files to my local pcb-fab production facility and therefore I want to be as 'mainstream' or 'industry-compatible' as possible.

The more I look at it I just don't think Frizing is quite suited at the moment for the need I've got, simply because it's still so new.

So I think I'll be using KiCAD for this one, although I might well document the other circuit I'm working on in Frizing as it uses standard parts there won't be any faf having to define footprints etc.

projects/managed_a_b_switch.txt · Last modified: 2013/06/28 11:59 by gareth
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