Power Supply in Observatory

[kirkster501]

Starting to think about what PSU(s) to use.  Is it best to use one for the mount and another for the camera/FW?  Or feed them all from one [bigger] PSU?

I was looking at this one:

http://www.maplin.co.uk/p/maplin-69w-dc-fixed-voltage-bench-power-supply-xm22y

EDIT: Apologies if this is in the wrong section, not sure where else to put it....

[damnut]

HI There,

It really depends on what else you intend to power from this, if you subsequently wish to power dewstrips then you need more ampage. This is for light power drain of a cb radio. If you only want mount & camera then should be fine, just check the tolerances on the voltage  so that they will run with a constant 13.8v provided by the psu.

[kirkster501]

Thanks Damian.  I'd want to power the mount, CCD Camera + FW and dew heaters for imaging and guidescope.  Maybe a focuser too one day and a USB hub..... So a lot of stuff.  Happy to  buy a bigger Amperage model.  Just wondering it the mount should be on a separate PSU?

Also how do you guys get the power from the bench PSU to all the gear on the Peer?  Run multiple power cables or have some sort of power distribution system atop the peer?

[Tinker1947]

The PSU you have listed is a 3amp 24/7 or 5amp @ 50%, i started with one then another then a 20amp, you may do better with a 30amp 13.8v  i would have gone for the one listed.....

http://www.maplin.co.uk/p/moonraker-375w-switched-mode-dc-variable-voltage-compact-bench-power-supply-n87jn

[Scott]

I have a 30Amp tranny with two outputs. I use one for mount/dew and one for the laptop (saves on additional 240v outlets). I also use a leisure battery for my ccd to keep it away from voltage drops caused by other devices (I intend on getting the atik mains power supply to eliminate this). 

[kirkster501]

The PSU you have listed is a 3amp 24/7 or 5amp @ 50%, i started with one then another then a 20amp, you may do better with a 30amp 13.8v  i would have gone for the one listed.....

http://www.maplin.co.uk/p/moonraker-375w-switched-mode-dc-variable-voltage-compact-bench-power-supply-n87jn

That's the one I will get.  I would imagine that can amply power the whole shebang...  Gee, 30A is a lot!

[damnut]

Hi There,

I would run one cable to the pier. I  am doing a distribution box for Pete Sullivan (tweedledee on ems) so in effect run a single 12 v to the pier then run off from there.  I can pm the pics if you like as I have removed them from EMS. There is a psu in maplin for about £90, but if you can find a spot for one of Baz's leisure batteries then you would probably do better by feeding from that. There are numerous projects for doing so. Also do check that if you use 13.8v that the camera and mount can take that constant extra nearly 2v.

My box is going to feed 4 dewstrips, camera, netbook, 2*USB pass through, spare 12v op.

[kirkster501]

How did you guys adapt the Atik CCD power cable from cigarette type to ring/banana plug type?  Is the Atik tip positive?  Do the Atik's work OK off of the 13.8v?  A polarity reversal could be rather expensive!

I am thinking of making a power distribution box at the peer.

[Scott]

Hi There,

I would run one cable to the pier. I  am doing a distribution box for Pete Sullivan (tweedledee on ems) so in effect run a single 12 v to the pier then run off from there.  I can pm the pics if you like as I have removed them from EMS. There is a psu in maplin for about £90, but if you can find a spot for one of Baz's leisure batteries then you would probably do better by feeding from that. There are numerous projects for doing so. Also do check that if you use 13.8v that the camera and mount can take that constant extra nearly 2v.

My box is going to feed 4 dewstrips, camera, netbook, 2*USB pass through, spare 12v op.

post 'em on here damian if you don't mind. I wouldn't mind a looksy

[Gina]

Atiks work fine off 13.8v   The tip of the cig plug is +ve.  Just make sure you fuse everything suitably - just in case.

[kirkster501]

So you also fuse stuff between the PSU and the device too then Gina?  Add an inline fuse on the +ve?  Is that a "floating" fuse inline on each cable or part of a power distribution device at the peer?

Now that I am [at last] building my permanent setup I am trying to visualise how to cable all the gubbins in whilst minimising the rat's nest of cabling required. I don't want to have to run umpteen cables under the obs floor between the obs desk and the peer!

EDIT: Just seen your power distribution thread Gina

[JonC]

If your after high capacity power supplies its worth keeping an eye on the amateur radio retailers, several sell second hand equipment. Looks like several sell on ebay now.

[damnut]

The box had to have a flat back and right hand side panel as it is being fitted to a 14"xti dob

So a simple 12v fused feed to the base, inside stripped  4 dewstrip controller, 12-20v inverter for laptop, 2 usb pass through ports, 12v out for camera, spare 12v Marine connector in, aviation grade keyed out.

[damnut]

Duuh the inside,

Spaghetti junction

Done

Kept the rear of the dew controller to epoxy in to protect the pots and led's. The inverter also epoxy in place.

[Horwig]

Power supplies is that area where there is never a simple answer. I'm personally playing safe in my obsy, in using two PSUs, and both analogue types, so no nasty switching spikes anywhere.

I've got one that just powers the ccd and the usb hub, and the other one does everything else, mount, dew straps and dome. At least, that way, if there are any nasties, hopes are that the signal path from the ccd will be clean.

They are both Maplin bench supplies, the 'clean' ccd supply is rated 5Amps , 9amp surge, the xm21, the other 'dirty' is an older 10 Amp version, xm19 I think. Both are really overkill for the current drawn, but then there is never any danger of the voltage dipping under load, and no danger of introducing nasties.

PSUs are cheap compared to everything else, and no need to get a shiny new one, just whatever is cheap on ebay, but stay analogue, not switched mode, at least for the imaging kit, you can probably get away with switched mode for the 'dirty' supply.

Just my biased opinion.

Huw

[damnut]

Agreed Huw, anything to stabilise  either spikes or brown outs helps. The above goes onto a base of a dob that is being moved around to dark sites.

Hwyl!

[mhard26339]

The PSU you have listed is a 3amp 24/7 or 5amp @ 50%, i started with one then another then a 20amp, you may do better with a 30amp 13.8v  i would have gone for the one listed.....

http://www.maplin.co.uk/p/moonraker-375w-switched-mode-dc-variable-voltage-compact-bench-power-supply-n87jn

This is the one that I have and it works like a dream with multiple outlets, some variable and different wattage. I mix this with use of the power supplies that come with the mount, camera, focusser etc; when I tried to combine into one I had nothing but trouble but others seem to work with it, I have seen Tinkers set-up and his works fine

Regards

Mike

[gorann]

I am a bit confused now and maybe I missed something. Why is this a problem? When you have an observatory why not just have a big car battery there? I use a normal 80 Ah 12 V car battery (costs 50 Euros) and a car battery charger (one of those small modern ones that conditions the battery and can be connected all the time, another 50 Euros). I charge the battery daytime, and just to be safe I disconnect the charger when I use the current at night (maybe unnecessary but I am not 100 % sure that the charger could not interfere with the equipment). An advantage with a battery is that you have no connection to the mains and therefore no chance of running into problems with ground loops that may cause problems with some cameras. Since I have a warm control room in the observatory, I keep the battery in there to help it to keep the voltage up during cold nights, but that is probably not critical (cars do start in the winter). From the battery I have a permanent cable to the mount with multiple outlets, and another cable to the winch that I use for the observatory roof. I think you need to work hard to empty out 80 Ah in a night -  have not ever got close to do that. Still, if you need more Ah, just add another battery.

[damnut]

Hi Goran,

You would need a 'leisure' battery as it is designed to release charge over a long period, rather than a car battery, where demand is high for a short period and is then recharged via the alternator. That's what my box is designed to work with.

[Physopto]

Hi Goran,

If you keep the battery in your warm room it should be in a sealed battery container with a vent to the outside. When on charge it may depending on the charge status vent hydrogen. Any spark can cause a nasty explosion in the presence of hydrogen. A build up of hydrogen may not exit the room before you enter and switch on an appliance. Costly in many ways!

Regards,

Derek

[Corpze]

I run my obsy with one of those china "switched 12v pus" 12,5A but planning to upgrade my obsy with fully remote control, all electronics mounted in a weather sealed cabinet with DIN-rails.

How ever, i am a bit confused about the switched china PSU. Would´t a linear be much better regarding EMI etc.?

/Daniel

[gorann]

Regarding hydrogen, I thought that this was a problem with old chargers that would overcharge the battery unless disconnected in time, but you got me worried and sent me surfing the net a bit, but I now feel reassured that this could only be a problem if you are overcharging the battery in a small compartment. Yes, a little bit of hydrogen is produced (much less than during overcharging), but using a modern smart charger (e.g. http://www.ctek.com/cy/en/page/whycharge/smart-battery-charger)in a 10m3 room should not be a problem, see for example http://smartercharger.com/faq/ or http://www.powerstream.com/how-to-use-a-battery-charger.htm. People use these chargers on their expensive Mercedes (which has the battery in the non-ventilated trunk).

I assume one could buy a slightly more expensive "leisure" battery (like the ones caravan owners use for watching TV) rather than a car battery, but so far the ordinary car battery has done its job excellently for me. The difference is that leisure batteries take it better to be close to discharged, but as long as I only use less than 40Ah of the 80Ah in a night my bet is that it will last a few years.

[Physopto]

Regarding hydrogen, I thought that this was a problem with old chargers that would overcharge the battery unless disconnected in time, but you got me worried and sent me surfing the net a bit, but I now feel reassured that this could only be a problem if you are overcharging the battery in a small compartment. Yes, a little bit of hydrogen is produced (much less than during overcharging), but using a modern smart charger (e.g. http://www.ctek.com/cy/en/page/whycharge/smart-battery-charger)in a 10m3 room should not be a problem, see for example http://smartercharger.com/faq/ or http://www.powerstream.com/how-to-use-a-battery-charger.htm. People use these chargers on their expensive Mercedes (which has the battery in the non-ventilated trunk).

I assume one could buy a slightly more expensive "leisure" battery (like the ones caravan owners use for watching TV) rather than a car battery, but so far the ordinary car battery has done its job excellently for me. The difference is that leisure batteries take it better to be close to discharged, but as long as I only use less than 40Ah of the 80Ah in a night my bet is that it will last a few years.

Hi Gorann,

You are almost correct. Modern chargers are better. But any battery that is charged up to 14.4volts will produce Hydrogen gas. Caravan manufacturers use chargers that only go up to 13.6volts as this produces little if no Hydrogen gassing. It is a safety aspect being close to gas heaters etc. Trouble is that this lower charge damages the battery as it never gets to a fully charged state. (About 85%)

All lead acid batteries will produce Hydrogen when being charged beyond that voltage no matter which charger is used. Any Hydrogen in a confined area is dangerous. A few years ago I had. 110 ah battery explode in front of me. I was extremely lucky. All the bits went upwards. I was only hit by the plastic bouncing back off the garage roof. I was covered in acid though and completely disoriented for a few seconds. Clothes just disintegrated even after getting them in the wash within 20 minutes. (Was showering very quickly). Also deaf for several hours. I.e. It is no fun!

I was an engineer for over 20 years and part of my job was to look after the ships batteries, I should have been more careful, but familiarity breed contempt!!!

As for the Merc I have never been in one or worked on one. But by law they will have to fit a vent tube from a sealed battery to the outside of the compartment. Jags had the same setup, battery in the boot, with a vent tube to the exterior.

No eyes no astronomy.

Derek

[kirkster501]

I have considered the use of a large capacity leisure battery but I think a dedicated power supply is better for my purposes.  Thankyou for the suggestion all the same.

I do need to make a peer head power distribution box.

[Bubbles82]

This is what I made really easy b and q for ip rated case £8. I was in a hurry and nearly brought the smaller one glad I didn't there is room for at least 2 more sockets in the future if needed