Monday, May 8, 2017

Cables....Be Gone !!!

Even though the skies weren't particularly clear this evening, Jonathan and I headed out to the observatory to tackle a few jobs that were on the list. A critical job that needed doing was to reconnect the dew strap to 12v power.  Since we'd replaced the mount electronics, the dew strap power couldn't actually be hooked up as the power had been routed through the original mount wiring (pretty much the only thing that was).

I wasn't keen on a temporary fix (we all know how these have a habit of becoming permanent) - and a "dream" of mine since we installed the paramount was to get as much of the cabling as we could to use "through mount" cabling to eliminate the risky "cable snake" that carried signal and power to the scope equipment.

Indeed when we rebuilt the mount, we were already supplied with the standard SoftwareBisque connector panel -  this was prewired with USB, a multipole pass thorugh power connector 5v and 12v outputs (though low current - we weren't too comfortable trying to drive the heater with the 12v).  We worked out this was almost enough for us to connect everything we needed bar a couple of items - one of which was the dew heater.

Custom wiring box on the mount dovetail plate
In the end we added to this two "network" sockets (connected with Cat5E cable) and two DC power sockets (locking 2 pin connectors) neatly mounted to the dovetail plate in a 3D printed enclosure. This provided all the connectivity we needed now, plus a little room for changes and expansion as we broaden our astronomical horizons.

in theory therefore, all that was required was making up a few cable connectors and we'd be to enjoy a cable-snake-less future....   Step one though is that we hadn't quite worked out the best (ie tidiest) way to get power into our extra power cables.  There were a number of spare "keystone" type connectors in the mount side panel we could have used - but unfortunately the locking connectors we used at the scope side were too big to fit.  We were originally planning to use "Anderson Power Pole" connectors but they didn't have an elegant panel mount solution.

The mount control panel showing our
newly installed Anderson PowerPole
connectors (top centre)
In the end the 3D modelling software and 3d printer again came to the rescue and we manufactured a custom "keystone" style mounting bracket for a pair of "PP30" connectors.  After adding further PP30 connectors to the lead from our 12V power supply (which would have been easier with the correct crimping tool for the job!) , and the appropriate 2 pin connector to the lead to the dew heater we were finally ready to test.  The dew strap (controlled by a PWM controller designed to handle LED lights) heated up properly and we were back in business to fight the dew. (if only it had been powerful enough to evaporate the clouds that had started gathering thickly!)

How many parts?
Of course one win doesn't make a successful evening - and with one device fully cabled up through our new mount wiring, sights were set on the rest of them!  Next in line was the biggest chunkiest cable - the power supply to our SBIG ST10XME camera.  From research this unit couldn't be driven from just 12v - the power supply has +12v -12v and +5v all supplied though a "DIN" style connector.

Making the cable connectors
The plan for this was to route through the small "Kycon" 4 pin connector in the SoftwareBisque wiring loom (labelled "power in" on the pic above).  this meant making up two adapter leads with DIN connectors on one end and "Kycon" on the other.  The DIN connectors were straightforward enough (once I'd checked, diagrammed, double checked and tested the pin layout) - but the Kycon connectors must be the fiddliest, most over-engineered plug on the planet.  It is supplied in no less than 8 individual parts, all in separate plastic baggies and a set of instructions.  The first one took some time to carefully assemble - though by the time I got to the second it was admittedly not quite as challenging.

Whilst it was a little nerve wracking to plug the new connector into the camera (even after double checking the polarity and voltage of the 3 voltage line pins), happily everything worked as it should have done and the camera spun up nicely.  The only remaining piece of equipment to handle was our Optec TCF Focuser.

As luck would have it, this one was probably the easiest.  The focuser connects to the controller by way of a 9 pin "D" plug cables to a modular RJ45 socket.  As a career geek, I've always got a handful of RJ-45s and a crimper at hand, so this was a 2 minute chop the wire smaller and connect on a new plug (which was even cabled as standard "T-568-B Spec").  Adding a small Cat5 patch cord at the control panel end and suddenly a long time dream was just about reality!

All that remained was to tidy and tie up the wring to keep it need and free from snagging on anything and to double check all our connections, and - importantly - to make sure everything still worked..

The process of moving from externally cabled equipment to using a "through mount" approach has taken a lot of planning - even at the early stages when we were tearing out the old control gear from the mount.  We needed to have our dovetail plate machined to take extra cables, and even create custom connector boxes.  Even with everything in place there was a bit of research required for the final cabling and it took a good few hours just to get everything built and plugged in.

The end result though is that now, as well as a much neater set up, we are free from the worry of the cables dragging on the floor or snagging on something - or of course one of us tripping on it.  We've also reduced the risk of damage to the cables, or a connector.


The end result - notice that all the cabling to the OTA now goes to the dovetail palte connector boxes.

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