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What wiring on the pier post?

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#26 MHamburg

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Posted 17 February 2013 - 08:55 PM

Maybe slightly better prices.
Michael
http://www.cableorga...-elasco/#prices

#27 Lord Beowulf

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Posted 19 February 2013 - 11:59 AM

Thanks to Alex for his article. That generally matches everything I've planned for on my observatory. I poured my piers with three different conduits, one for 120 VAC, one for 12 VDC with possible regulators for lower voltages (e.g. 3V) for running lasers, etc., and one for communication.

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Even after that I realized that USB was likely to be a problem and I might not have enough room in the 3/4" conduit for communication stuff, so I did a catch-all in the slab, running a 4" PVC pipe from the pier to near the wall.

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A couple of other things on the 12V supply. Definitely a large gauge wire is a requirement (planning on using good speaker wire for minimal inductance and loss) but I think regulation/surge suppression at the load is important too if you're using multiple devices on the same supply. Otherwise, steps in the current draw along that long supply line will cause surges at the various loads. My plan is to actually use multiple supply lines so that the power is split back at the source rather than at the load, which will help minimize that problem. I've also planned to add some regulation in the box for 5V/3V supplies for USB hubs, lasers, etc. that would reduce the need for wall warts out at the pier.

My other thought on the UPS is that while it makes sense to have any AC components supported by a UPS, in some respects using the UPS to run a 12V power supply is a bit backwards. Basically you're taking a 12V battery, up converting to 120V and down-converting back to 12V! My thought is to have a couple of deep cycle batteries tied to my DC supplies in such a way that the battery takes over if the power supply goes down. I'll have to look into diode protection, etc. on this scheme to make sure it works, but that seems like a slightly more efficient and longer lasting solution. Heck, hacking a UPS or two to run off the larger battery has also crossed my mind. That should keep things going for a long time!

Beo

#28 Alex McConahay

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Posted 19 February 2013 - 12:25 PM

>>>>you're taking a 12V battery, up converting to 120V and down-converting back to 12V!

I see what you are saying. But, really, the UPS is there mostly for power regulation, and for cleanup. I cannot imagine running for a long time without line power. And while it may seem like I am upconverting and then down converting, in fact, unless I am running off the UPS backup supply (i.e., the line power has failed), I am not upconverting at all, but just running off the regulated 110 volt.

>>>>>My thought is to have a couple of deep cycle batteries tied to my DC supplies in such a way that the battery takes over if the power supply goes down

Worrying about the needs of a couple of deep cycle batteries, with a float charger to keep them happy, is something I need not deal with.

But, to each his own. No doubt, your solution would work for you.

Alex

#29 Mary B

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Posted 19 February 2013 - 05:14 PM

Automatic DC switchover + float charging for your battery http://www.westmount...oducts_id=pg40s

#30 Lord Beowulf

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Posted 21 February 2013 - 08:02 PM

>>>>you're taking a 12V battery, up converting to 120V and down-converting back to 12V!

I see what you are saying. But, really, the UPS is there mostly for power regulation, and for cleanup. I cannot imagine running for a long time without line power. And while it may seem like I am upconverting and then down converting, in fact, unless I am running off the UPS backup supply (i.e., the line power has failed), I am not upconverting at all, but just running off the regulated 110 volt.

>>>>>My thought is to have a couple of deep cycle batteries tied to my DC supplies in such a way that the battery takes over if the power supply goes down

Worrying about the needs of a couple of deep cycle batteries, with a float charger to keep them happy, is something I need not deal with.

But, to each his own. No doubt, your solution would work for you.

Alex


Hey Alex,

I wasn't criticizing your solution. That's actually the way I ran for a year or so after pouring my piers. I had an intermittent power failure problem that I originally attributed to poor country power service, but it turned out to be a bad breaker contact in the old breaker box that I replaced.

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At any rate, as I've been considering the finished design for the observatory, it just struck me that using UPS for all the 12V stuff was less efficient than running straight from the battery. It also increases the size of inverter you need on the UPS to handle all the load. While we generally aren't talking about major loads, it's still a consideration. Of course the one thing I'm considering now is whether or not to actually put the AC outlets on the piers on a UPS that's wired back in somewhere. I wouldn't want to have to put a big UPS underfoot at the pier! Something to think about...

Beo






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