Observatory Power supply ?

[RobertM]

I'm thinking of buying a power supply to go in my observatory and was just wondering what type people use and why:

Switched mode, Linear or Leisure battery.

Thanks
Robert

[Carole]

I'm cabled to mains in my obsy with armoured cable.

Carole

[RobertM]

Thanks Carole, I have that as well.  I'm thinking more of the 12v supply to the telescope and equipment in the observatory.

Robert

[Carole]

I have a Mains to 12V adapter plugged in in the obsy.  With a splitter plugged into that for everything 12V.

You probably want something a bit more sophisticated though like one of the multi hubs, so I'll butt out.

Carole

[NoelC]

I'm using an old Radio Shack 7A supply at present; just because I had it available and because its my impression that the old linear power supplies don't have any nasty switching transients on them.  But I'm looking to replace it with something heavier (in current terms).  I also still have the 12V distribution via a plug board bolted to the mount - which is also up for replacement due to the risk of shorting out the 12V if you plug stuff in the dark. I run the PC of it's own lump (after I blew one up) although it's also 12V. So I'll be interested in what you come up with.
I was thinking of something like a 20A supply with possibly a Pegasus PPB to distribute the power (which also has dew control).
https://www.makers-hut.com/product/dc-5v-12v-24v-rainproof-regulated-switching-power-supply-psu-transformer/ (20A- £20 +PP)
https://pegasusastro.com/products/pocket-powerbox/ppb/ (£180)
I've come up with various schemes for a self build 12V distribution box (with independent short circuit protection), but it gets rather complicated if you try to control it electronically; which is where the PPB comes in.

[RobertM]

Hi Noel,

Those are interesting options.  I already have the MHP V4 though I wish I had the Ultimate Powerbox V2 as that can be controlled automatically from within my astro software.  If that V2 Power Box had a 1GBe interface then it would be a no brainer.  My main problem is what to power it with...

I was thinking that it has to be a clean noise free source but then again Camera manufacturers supply cheap 3-5A switching units which must be quite noisy electrically plus there is all the noise that dew bands generate.  Soo... I think that whether the PSU is a Switch mode or Linear probably makes no difference.  More of a difference is the power output to ensure there is plenty of spare capacity.

Something else worth mentioning is that Linear PSU's are generally no more than 40% efficient so that's a lot of wasted power.

At the moment I'm looking at this: https://www.amazon.co.uk/Alinco-DM330MW-MkII-switch-supply/dp/B0040YGOSE/ref=sr_1_1?keywords=alinco+dm330mw&qid=1572270443&sr=8-1

Robert

[ApophisAstros]

At the moment I'm looking at this: https://www.amazon.co.uk/Alinco-DM330MW-MkII-switch-supply/dp/B0040YGOSE/ref=sr_1_1?keywords=alinco+dm330mw&qid=1572270443&sr=8-1

Looks like an old CB radio
Roger

[Rick]

At the moment I'm looking at this: https://www.amazon.co.uk/Alinco-DM330MW-MkII-switch-supply/dp/B0040YGOSE/ref=sr_1_1?keywords=alinco+dm330mw&qid=1572270443&sr=8-1

Looks remarkably similar to the one I've been using to run various bits of radio kit for a fair few years.  (Paid quite a bit less than 130 quid for it back then.) Mine hasn't revealed any nasty habits yet, but it doesn't run 24/7. Note that it'll put out 13.8V by default, but you can adjust that.

[RobertM]

Thanks all  for your comments, I'll try the Alinco.

Rick, that one has an adjustable output so I can account for some volt drop under load and get 13.8v to the business end.  It also has less the 15mV p-p ripple so should be good on that front too.

Robert

[Rick]

Mine's tweaked slightly, and run in fixed voltage mode. I think there's a preset pot and a little switch on the back to allow that. Not sure how far either way you can adjust things with the preset.

[RobertM]

It can be adjusted up to 15v, I think there is also a switch for fixed voltage like yours.

Robert

[NoelC]

Thanks for the link; the Alinco looks very interesting (and about 3 times the price of anything I was considering).  I had not considered the effects of supply noise to that extent before; can you measure it (and can you see the effects of it)?  I assume the camera will filter out the effects to a large extent as the supplies sold by the camera companies don't seem very clever.  Whats your view?

On the load argument; "More of a difference is the power output to ensure there is plenty of spare capacity."
Surely the bulk of the load apart from dew bands goes into stuff that's not used when imaging or which is a linear (coolers)? Granted ripple goes up with load, but is paying for more capacity than you use going to reduce noise?

https://www.nevadaradio.co.uk/cb/cb-power-supplies/avair-av-2025d any interest?

[RobertM]

It's an interesting question Noel.  My electronics background is telling me that lower noise is better (where there is any analogue signal involved) but clearly even QSI provide a cheap switching mains adaptor - maybe it doesn't matter too much.  I'd prefer to err on the cautious side so I ordered that PSU yesterday and surprisingly it arrived today.  It could be the one you found is better but I read the reviews about the Alinco on a Radio Ham website and they were all good.   If I'd seen the other one then I would have checked the reviews to make sure it wasn't a duffer and probably gone for it instead.

Regarding power output, I don't believe is running things at 60% or more of their rated output continuously so for me the supply has to be at least 40% overrated and preferably more.  So what is 40% overrated ?  For me that would mean about 3-4A of observatory equipment (cloudsensor/USB3 hub/security camera etc.) plus 2-5A telescope side (dew bands, cameras, on mount PC, focuser), that's about 9A peak + 40%.  If you add that I wanted low noise then the choices whittle down quite a lot.  There was a linear supply I saw that had 10mV of ripple but that weighed in at over 7kg !

... and yes agreed I don't want to pay more than is necessary but quality also matters as it'll be around for a while (hopefully).  The Alinco is made in Japan so likely to Have higher quality components (it certainly feels well made).

Robert

[Rick]

For comms kit it's good to have minimum ripple and a way to shift the whistle should it get in the way. Most modern commercial kit ought to have enough filtering inside to cope with stuff coming up the power lead, but radiated RF is another matter, and that's where the twiddleing can come in handy. I'd expect decent astro kit to be similarly protected, and it shouldn't be RF sensitive...

Worth having a PSU that'll give a bit more than you need, but if your peak load's somewhere down round 10 amps then a smaller supply would probaly be fine. Mine ticks over at an amp or two, but can easily kick past 20 on transmit...

Might be worth browsing the offerings of comms suppliers like Moonraker ( https://www.moonraker.eu/ ), Martin Lynch ( https://www.hamradio.co.uk/ ), or Waters & Stanton ( https://hamradiostore.co.uk/ ).

[The Thing]

Hi Noel,

I am now using an old 16v laptop brick (Toshiba so may be reasonable quality) feeding a 12A Step Down Module Buck Power Supply Adjustable Board With LCD Digital Display from ebay . I have checked the output with an oscilliscope and can't see any ripple and it runs everything except the mount which has its own power brick supply in the observatory. I use an very very old 240v distribution block originally intended for simplifying hifi etc. mains connections. I have looked at all the other solutions as discussed below and decided they were overkill. This power configuration can run everything if needed and shows a power consumption of around 3A when cooling the CCD, slewing, powering a 12v USB3 hub and running two dew heaters at their normal setting. The brick and step down device provide all sorts of short circuit and overvoltage protection between them and they recover (have done so far anyway!) and live in a waterproof garden mains connection box from Toolstation.