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Shibby

Power distribution

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Hi all,

I'm currently ordering parts for my observatory build and was hoping for some advice on the DC power distribution.

I already have my 30A bench power supply with short circuit protection. I have 2 heavy cable running this 12v output to the pier. I could do with a sanity check on the rest of the plan, as I have no experience and am a bit confused having read lots of different information.

Can I run this into a fuse box, e.g. http://www.12voltplanet.co.uk/low-profile-standard-blade-fuse-box-side-terminals-8-way.html

With appropriate fuses installed for each device (camera, mount etc), I then connect cables with blade terminals - but what sort of cable do I need for the devices? Will they need to be well shielded even at low current? Or will this sort of thing do: http://www.12voltplanet.co.uk/2-core-thin-wall-auto-cable-2-x-11-amp.html  -  It doesn't look very flexible, though.

Also, and I'm sure this is a very dumb question, how is it best to connect the negative wires - a separate terminal block?

Help and advice much appreciated (Please do not assume I know anything!)

Thanks

Edited by Shibby

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Hi Shibby

Look at the gauge of wire on the power units supplied with your camera, mount etc.

That's the sort of thickness you'll need from your fuse box to each device.

Even better, look up the amperage of each device's power supply.

Julian's 6A cable would be ample for the mount, I'd guess the camera needs far less.

Michael

 

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The wire that you mention in the OP is suitable for 11 amps.  So should be just fine.

 

Here's a picture from my power box.  I've got 2 screwed cable busses.  One for positive and one for negative.

The cable that I'm using is rated for 50 amp.  (I like overkill)

The crimps are only rated for 10 amp each, so it's on par with your cable.  The blade fuses are matched to their applications.  4 * 10 amp a for the automotive, 3 * 5 amp for the USB sockets and the voltage meters.   The other fuse 20 amp I think, is connected to my telescope power box (it's a long story)

5793a24fc5821_Photo23-07-2016162113.thumb.jpg.d7b20b65393defbb418725c100169bf8.jpg

 

Hope this gives you an idea.

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Thanks very much for the responses all!

@Dr_Ju_ju Might get one of these for the mount at least.

@michael8554 Thanks, yes it should be ok but I'm not sure how flexible because it's flat?

@cjdawson Very helpful indeed, thanks! I'm not sure I 100% understand, however. Are the connections on one side of your fuse box all inputs? (the input is not shared?)

So, just to make absolutely sure I'm not getting the wrong end of the stick here (which is quite possible), is this simple setup correct? Crude diagram time...

DC-power.PNG

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Are the blade fuses fast blow or slow blow?  My understanding (i.e. probably wrong) is that the 230v >12v power supply should be protected by a slow blow fuse, but that the appliances themselves are best protected using fast blow fuses.

http://www.doityourself.com/stry/slow-blow-fuse-vs-fast-blow-fuse

 

 

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To answer the question.   The red wires are all live.   On the left side they are all screwed into a bus bar

Similar to this

https://midsummerenergy.co.uk/buy/cables-and-connectors/Busbar

The 12v live feed in comes in at one end.  Then each of the individual wires run from the bus bar to a seperate input on the fuse box, through the fuse, and out through it's own wire.

This link provides a better link what to expect from the fuse box

http://www.ebay.co.uk/itm/like/281370441610?chn=ps&adgroupid=40208487538&rlsatarget=pla-278029347814&abcId=923846&adtype=pla&merchantid=109724805&poi=&googleloc=1007070&device=c&campaignid=738085096&crdt=0

 

after that, yes, each wire feeds on device, then the black wire goes to another bus bar, which then goes back to the battery.

 

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The cable I linked to, is small enough (5mm overall diameter) & very flexible, so is able to cater for all external power connections, including mount, cameras etc.

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I fused all the outputs of my power box.  The Mount and Astrozap Controller I fused at 5A and everything else (camera, filter wheel, focuser etc) at 1A.  Ample.

I also built a crowbar protection circuit that will sits across the PSU 12V output and blow the 12v car blade fuses if there is an overvoltage condition on the 12V rail that would otherwise damage my gear.  Not essential but worth doing for peace of mind when there is thousands of pounds worth of gear beign powered by that [relatively] cheap 12V LED PSU.  The whole box which is my USB and power distribution box cost me about £160 to make, including the Startech USB hub.

IMG_9124.thumb.jpg.3199c30d3ff7b9b71fa7282a376d4a4c.jpgIMG_9123.thumb.jpg.c9ae9f1c0447adc606a1fd6814231af1.jpg

Edited by kirkster501

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@kirkster501 That is one neat solution, love it!

@cjdawson Thank you for explaining, that all makes perfect sense now.

@Dr_Ju_ju It's also a very good price - think I'll get a good length of it ordered today.

Thanks again all, got things a lot clearer in my head now!

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