Power supply question

[DJT]

Have been fortunate enough to pick up an AP900. I would like very much not to fry it though.

Looking for best recommendations for a safe power supply. The mount will be in a permanent observatory, dedicated mains power etc, but am not a sparks and get a bit confused with regulated power etc.

I think I will be getting something like this but interested in knowing if there are other options
http://www.bintel.com.au/Accessories/Power-Supplies/Bintel-12A-Regulated/520/productview.aspx

Mount specs say regulated and filtered, 12v, 5 amps.
Thanks for advice

[White Rabbit]

I have this one from Jaycar. http://www.jaycar.com.au/productView.asp?ID=MP3802&form=CAT2&SUBCATID=999#3
It works very well, I also power my dew heaters of this at the same time.

Sandy

[Barrykgerdes]

I also use a quality 12v (13.8) regulated supply (not a switch mode) from Jaycar. Never had any power supply problems in 18 years with this type of supply that has good regulation and overload protection.

For field use I use a 12v 18Ahr sealed battery from Jaycar and a cheap charger I bought from the reject shop.

Barry

[DJT]

Thanks for responses, turns out AP had good info on power supplies on their site as well which I missed

http://www.astro-physics.com/index.htm?products/products

[Marke]

Its pretty hard to kill it with voltage , will easily run on 16v if you want to .
I have a big battery in the obs with a trickle charger on it all the time . I run my Mach1 straight off this at 13-14v no problem.

[DJT]

Thanks Marke
Out of interest, why a battery and what type of battery is it?

[RickS]

I've been running my AP900 on 13.8v for a year or two using a power supply that is a rebranded Manson (older version of the SPA-8330 on the Andrews site? http://www.andrewscom.com.au/site-section-04.htm).

The AP900 manual recommends 13-16V for best performance.

Cheers,
Rick.

[Marke]

Just a big 120Ah and I have everything running 12v except PC , its just safer and easier to pull off anything and take it away to a dark site if needed .

[JohnH]

Let me preface this - I am not a sparky either - but be careful with Jaycar power supplies. I had the same concerns in powering my G11. The advice was to use a slightly higher voltage so I chose a 13.8v non-switch mode PS (I believe these give a cleaner output) from Jaycar - this one:

http://www.jaycar.com.au/productView.asp?ID=MP3097&form=CAT2&SUBCATID=999#12

This I used to power everthing that was 12V - my mount, focuser and ccd camera. Seperately I hade a powered USB hub (5V) and, of course, the laptop (connected to the mains). Of course all the equipment is interconnected via the USB shield. Result? Fried my Sbig CCD.

The reason I believe - not a sparky - was not a ground loop but the design of the PS - it had a "floating ground", that is the -ve terminal is not 0v or earth grounded (despite the metal case and 3 pin plug) - all you can be sure of it the difference between the terminals is 13.8v - in my case once this 0v was connected to the laptop 0v via the USB - smoke. I now keep all the equipment isolated.

[DJT]

Ouch..unlucky. Will bear that in mind. Thanks for the tip.

[multiweb]

Over the years I had two of these (http://www.jaycar.com.au/productView.asp?ID=MP3802&form=CAT2&SUBCATID=999#3)and two of these (http://www.jaycar.com.au/productView.asp?ID=MP3078&form=CAT2&SUBCATID=999#3). They all died of a horrible death within 2yrs. One actually blew and disjuncted my house. And they weren't cheap at $170.00 a pop at the time. :rolleyes:

Then I had enough so I now use this one (http://www.jaycar.com.au/productView.asp?ID=MP3097&form=CAT2&SUBCATID=999#12)and one of these (http://www.jaycar.com.au/productView.asp?ID=MP3242). I haven't had any issues to date. I also use a step up DC to DC converter (http://www.jaycar.com.au/productView.asp?ID=MP3472)from Jaycar too, to get 16V for the Gemini out of a 12V supply.

[RobF]

I always power my CCD off a battery now John because of this. Everything else off a mixture of power supplies, battery. USB all back to laptop inside the house on 240V. Not willing to risk my CCD.

Would be interesting to hear what if any power supplies aren't "floating" design though? I thought regulated (versus switchmode) was best?

[DavidTrap]

Rob - isn't your battery just the same as a floating power supply here??

BTW, I'm not sure what the ultimate answer is?? I now have a PC that runs off 12V, so everything runs off a common supply. I didn't do this to avoid ground loops, but I hope it will be a useful side-benefit.

DT

[Tandum]

Not if you run every thing off the battery. Laptops are not earthed.

After the great lightning strike of Nov 2012, I recommend a UPS in front of everything.

[DavidTrap]

But Rob's post mentions a combination of batteries and other power supplies??

I thought a ground loop could occur if there is a potential difference between various the negative terminals of different power supplies, e.g., between the negative terminal of a USB plug connected to a laptop being powered from a 240V adapter, and the negative terminal of a CCD being powered from a 12V battery???

DT

Did you edit your post?? I didn't see the bit about laptops not being earthed??

[Tandum]

Yes that's right, Rob is a renegade, but show me a grounded power supply?

[RobF]

I had a run of QHY9 problems around the time I started running my rig from inside. That is, a few small power supplies into a power board back to 240V outside and the lappy plugged in to 240V inside. Outside rig run by USB extender lead from laptop. Theo thinks it was more likely moisture issues that have since been sorted.

Anyway, since then I've religously run a separate USB lead from CCD to laptop and run the CCD along off a battery. I like to think I'm a scientist, but heck there's probably superstition in here. Thus my questions - curious to learn more about the power supply issues......

http://www.reactiongifs.com/wp-content/uploads/2012/12/bill_murray_ghostbusters.gif



p.s. David - I wouldn't be worried if everything including lappy was off the same supply somehow, or powered off same battery bank as you probably would do at Leyburn.

[Garbz]

Many supplies are grounded. Look for those with 3 prong cables.



Yes that's true. It seems quite strange that a battery powered device can fry as a result of an earth loop as battery powered devices by their very nature "float". I have a similar setup, my laptop is earthed by virtue of the powersupply it uses, and my telescope power floats. If I plug in a USB cable you can see a brief spark as everything is brought to the same potential followed by perfectly working equipment.



There is no "regulated" vs "switchmode" a switchmode supply is a form of regulated powersupply. The alternative to switchmode is "linear". Both have their benefits.

Switchmode generates a stable voltage by rapidly switching a circuit on and off across a reactive component and then filtering the result. They are very stable, small, light, energy efficient, capable of large loads without getting hot, but they do exhibit noise typically within their switching frequency (often between 60kHz and 1MHz).

Linear regulates power (downwards only) in a resistive way, burning any difference between the input voltage and output voltage away in heat. They are not at all energy efficient. They rely on heavy transformers and get very hot very quickly as the current increases. They produce a very low noise output.

Both types of powersupplies can be floating, Both types of powersupplies can be grounded. Metal case powersupplies will nearly always be grounded types (for safety). As for which is better? Neither. Some people will swear that linear is the only way to go, others like myself have seen switchmode supplies power the likes of highly sensitive spectrum analysers costing in excess of $200k.

The answer as always is you get what you pay for.

[DJT]

Thanks for Contributing to the thread.

The Mount is tucked away at the couriers so will be picking something up on Tuesday to power it when I get back from the long weekend. Will mull over all the comments and hopefully pick the simplest solution

Thanks for the feedback

Cheers

[Tandum]

A 3 pin plug doesn't mean it's grounded. Most are double insulated.

[Garbz]

Indeed my two statements were independent from each other. Many supplies are grounded. But no supplies with a two pronged cable are, so at the very least you need a three pronged cable.

Three pronged cable often implies metal case.
Metal case often provides an earthing bolt.

Most of the earthed supplies I've seen provide an option for lifting the earth. In the case of supplies like the bench supply posted above there's often 3 terminals, red, black and green, and they come with a little metal jumper that connects the black to the green.

[DJT]

Yup, picked up this one last week. Cheers all.