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12 Volt mains power supply


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Can anybody recommend a good regulated mains power supply the drive system on my Celestron Edge HD on a CGEM DX mount.  Most of the Celestron & third party accessories need 12 volts DC but a quick search only found units like the Celestron power tank & reviews of this item were not particularly encouraging. This power supply would be housed in my backyard observatory with available 240 V mains power.

Any thoughts about the tracer lithium polymer batteries? as a field supply source. These could be potentially good but I'm cautious as they would need to handle the Astro Zap Dew Shield & of course the mount itself so I'm not sure if I would need multiple batteries or is 22 AMP hours going to be enough. The CGEM at max pulls 42 watts -not sure about the dew shield but the controller is only rated at 5 amp for 4 separate outputs.

Any advice would be appreciated.

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i run a 11.1v  @2200mah , my draw is about 60amps 

it lasts me 7 mins .

theres other things to. 

lipos require careful management, they need an LVC ( low voltage cutoff) 

system fitted and a low voltage warning alarm. ( a lipo when drained to much becomes a fire/explosion hazard)

Safety, a short in the lipo pack is going to cause a chain reaction. for an 11.1v battery thats three seperate cells.

each one a small explosion. when lipos let go they let go with style ( in RC we loose the electrical system and possible the machine itself from fire).

stick with lead acid in the field.

as for power, i would go a 12v bench supply, if you have a half decent old computer PSU

that to can be converted into a regulated power supply.  ( we do this alot to run 12v lipo chargers and nimh/nicad chargers )

saves us flipping the car bonnet. just google "computer psu to bench supply mod ", you can have 12v - 5v and 3.3v

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I have two 12V supplies, both snagged off ebay:

http://powersolve.co.uk/psl400bp-series

http://www.ebay.co.uk/itm/NEMIC-LAMBDA-EWS300P-12-12V-27A-DC-Power-Supply-INPUT-110V-or-220V-adjustable-/181346415391?

Either would be suitable. The Nemic supplies 27A to my imaging rig outside (or it will when I get the cable installed) and the voltage is well regulated with low ripple. I'd forgotten what an absolute pig 4mm cored armoured cable is like to work with!

ChrisH

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this model is recommended on 365 astronomy for your mount. might be worth speaking to them and checking. the Baader equipment is very well thought of.

http://www.365astronomy.com/baader-12v-5a-outdoor-telescope-switching-power-supply-p-3697.html

The narrative in that ad sounds like snake-oil to me, to be honest.

"When used outside in the cold the voltage will reduce with temperature." "Already at -10°C the remaining voltage output may have gone down to only 10.5 V" That might be true for batteries, but it's increasing heat that causes a transformer to lose efficiency.

And £48 for a simple 240V to 12v transformer? That looks like at least three times what I'd pay for that:

http://www.amazon.co.uk/s/?ie=UTF8&keywords=12v+power+supply+5a&tag=googhydr-21&index=aps&hvadid=24515934174&hvpos=1t1&hvexid=&hvnetw=g&hvrand=1080561342964055095&hvpone=&hvptwo=&hvqmt=b&hvdev=c&ref=pd_sl_5njlreq0ey_b

And calling it an "outdoor" power supply when it has a standard power connector on it is plain dangerous. That doesn't look to be rated for outdoor use at all. i'd bet my mortgage that it doesn't have a NEMA rating for outdoor use.

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You need more than 5A IMHO for an imaging rig. Tot up the max draw for all (and possible future) equipment and then add 50%. My 30A supplies will cover anything I'm likely to use. The OP suggests the PSU will be housed in an obs so don't need to worry about it being an outdoor type. The reason I have two is I have one fully wired up for inside use (to take flats/darks/generally muck about with the rig) and the second wired up for external use terminating at the pier. I'm just now putting the remote connection box together using weatherproof 12V connectors.

These are the PSUs

IMG_0285_zps7da905ad.jpg

These are the connectors and box that will attach to the pier:

P1030035_zpse38aa680.jpg

And I will use this DC-DC convertor to power the laptop, together with a 5V buck convertor to power the USB hub. That way I don't need any 240v mains supply at the scope end at all.

P1030032_zps4e337665.jpg

ChrisH

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Now attached to my pier - but no supply cable laid in yet :(

IMG_0288_zpsa73ee056.jpg

IMG_0290_zps70fcab66.jpg

IMG_0293_zpsaa86e117.jpg

ChrisH

Chris, that all looks great.

Just a couple of questions. Could you provide a quick wiring diagram because I cannot see some of the wiring, and secondly, what is the box on the underside of the lid in between the sockets?

I am getting to work on this myself too! :D

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Chris, that all looks great.

Just a couple of questions. Could you provide a quick wiring diagram because I cannot see some of the wiring, and secondly, what is the box on the underside of the lid in between the sockets?

I am getting to work on this myself too! :D

Well the wiring simply links all the +'s and -'s together, apart from one socket at the bottom left. That one supplies 5v not 12v and is powered by the buck convertor (that little box in the middle, which is fed 12V and outputs the 5v needed for the USB hub). Power will come in through a gland on the bottom edge and is linked to the sockets using the little white block connector you can see in the picture. All the plugs are fitted with fuses according to their current requirements and this was done when swapping plugs from the originals to the waterproof ones when I also swapped fuses just re-using the manufacturers fuses (the Atik camera and filterwheel, the focuser, dew heater and Losmandy Gemini). I need to mark the single 5v socket and plug with a different colour to remind me it's 5v and not 12v! It won't beidiot proof (it's physically possible to plug into the wrong voltage socket) but then I'll only have myself to blame if I blow the USB hub up using 12v :-)

ChrisH

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Well this is the first time the whole thing has been powered up outside, and nothing has blown up yet! Wiring might look a bit messy but I can fettle that a bit. Waiting for the clouds to roll in so I can put it away again...

IMG_0295_zps9dffb05f.jpg

IMG_0297_zps9ac3f155.jpg

IMG_0294_zps0af8eb3f.jpg

ChrisH

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That's cool :) I realise I'm short one socket (for the laptop I have to use to focus the guider). There's room in the box for another when I can get around to it.

ChrisH

How did the power unit perform last night?
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How did the power unit perform last night?

OK for the most part, but then my mount failed to slew once (motor stalled) indicating it couldn't draw enough Amps so I powered that from a battery. I wasn't surprised because a) the voltage was set low (11.8v at the pier) and B) the cable is way too thin @ 0.75mm per conductor (I've got some much thicker 4mm armoured cable but can't install it yet due to some landscaping that is about ot happen). So I have ordered some thicker 2-core cable (2mm) to use temporarily and I also increased the voltage to 13.8v. I will be trying again tonight but without the thicker cable I'll power the mount from a battery again. It might work without but it's too much hassle to have to reset the mount in the middle of a run.

ChrisH

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OK for the most part, but then my mount failed to slew once (motor stalled) indicating it couldn't draw enough Amps so I powered that from a battery. I wasn't surprised because a) the voltage was set low (11.8v at the pier) and B) the cable is way too thin @ 0.75mm per conductor (I've got some much thicker 4mm armoured cable but can't install it yet due to some landscaping that is about ot happen). So I have ordered some thicker 2-core cable (2mm) to use temporarily and I also increased the voltage to 13.8v. I will be trying again tonight but without the thicker cable I'll power the mount from a battery again. It might work without but it's too much hassle to have to reset the mount in the middle of a run.

ChrisH

I used 15a cable from Maplin. Good stuff. I use it for all of my DIY Astro jobs :D
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  • 1 month later...

Love the box, Chris. Can you tell me where you bought the lockable 12V plug and sockets? Does it make any difference if you wire them in seies or parallel?

Tinker, I see you have a Fusion power supply there. Are they any good? I was thinking of just going for the 30A unit which should cover all my needs.

Thanks

Ken

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The Fusion PSU atm only runs a dew heater strap, the internal fan runs 24/7 its not to noisy but further down the road could require a replacement, i wish i had gone the 30amp route having had a couple of 30amp PSU's in my amateur radio days i knew in my mind it was the way to go....

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  • 3 months later...

You need more than 5A IMHO for an imaging rig. Tot up the max draw for all (and possible future) equipment and then add 50%. My 30A supplies will cover anything I'm likely to use. The OP suggests the PSU will be housed in an obs so don't need to worry about it being an outdoor type. The reason I have two is I have one fully wired up for inside use (to take flats/darks/generally muck about with the rig) and the second wired up for external use terminating at the pier. I'm just now putting the remote connection box together using weatherproof 12V connectors.

These are the PSUs

IMG_0285_zps7da905ad.jpg

These are the connectors and box that will attach to the pier:

P1030035_zpse38aa680.jpg

And I will use this DC-DC convertor to power the laptop, together with a 5V buck convertor to power the USB hub. That way I don't need any 240v mains supply at the scope end at all.

P1030032_zps4e337665.jpg

ChrisH

Well that was today's job - finished the pier power distribution box :)

P1030036_zps43cf352b.jpg

ChrisH

Hi,

I have just come across this thread, and have bought some of the same 12v sockets with the twist lock system as yours, but where can I get the matching 12 plugs from to,use in them so I can take advantage of the twist lock system, I can only find normal ones which do,fit, but would like the matching ones really

Appreciate any help

Olly

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