12 power supply for ST7 - suggestions?

[rogerg]

Anyone have experience with 12v power supply for the SBIG ST7?

I'd like to use mine on my portable setup out in the field, running from 12v. The SBIG 12v power supply is pretty expensive - something like AU$280 I'm guessing, by the time I get it.

Another alternative I'm aware of is buying an inverter ($59 for a cheap one, $230 for a better quality one, both 150w).

Any other options that are more affordable than $280? Surely the power supply SBIG sell must be available elsewhere cheaper, or something similar?

Thanks for any info,
Roger.

[janoskiss]

Sealed lead-acid batteries are not so expensive. 12V, high current, lots of amp-hours, what more do you need? :)
Jaycar or other electronics shops carry them.

[Starkler]

Try to find out the current consumption specs of the sbig, then substitute with a regulated 12v supply from DSE, Jaycar etc.

Where you might get caught out is if there is a custom connector plug/socket arrangement.

[rogerg]

Hi guy's..

Problem is the ST7 requires a few voltages - 12v, 5v and one other I think(can't remember right now and don't have the spec in front of me). So while I have sealed lead acid batteries for my laptop & losmandy (mainly use a 46 amp hr and 17 amp hr battery) I need the correct other voltages, and pin configuration of the plug etc.

I'm not bad at soldering, so wouldn't rule out making the plug myself, but was hoping to avoid it, for fear of doing something wrong with such an expensive item.

I bought the huge 46amp hr battery with the intention of running the camera off it (along with the losmandy & laptop), but the problem is getting the desired voltages & plug out of it.

Roger.

[Kyecat]

Roger

Perhaps an inverter running a recycled PC power supply. Pc supplies usually have 5 And 12 volts. 300w inverter about $70 from Aldi stores and PC supply from next council clean up day or recycling center. The inverter has the advantage that it can be used to charge other things (laptop, phone,camera batteries etc) without buying special 12v chargers. Disadvantage is loss of effiency swapping voltages backwards and forwards.

Graeme

[rmcpb]

FWIW I have just made a simple voltage regulator from a **** Smiths kit that allows you to regulate the voltage from a 12V supply. I can dial up any voltage I want so long as its less than 12V. Seems to be stable and probably worth a look at about $7 plus the box.

Just a thought :)

[RAJAH235]

Roger, depends on current req'd at the stated voltages. 12 volt will be low? (straight off the battery, doh!). The 5 volt will be a little higher, but there's an easy solution. A very easy-to-make, regulated supply using either an, LM7805, 1 Amp output, or an LM317 or 350 for higher currents. :D L.
ps. They ALL must be adequately 'heat sinked' tho!
pps. Hope you can make them out. Darn jpeg compression..
ppps. They are "ALL VOLTAGE ADJUSTABLE". see LM317 info.....If you need the larger sized pages, PM me..

[cjmarsh81]

If you do run it from a 12V battery I would still use an LM7812 regulator. A car battery can vary from 11.5 to 14.4 Volts depending on the charge in it. I don't know how sensitive your equipment is, but I would be using a regulator to be safe.

I do not like the idea of running a recycled pc power supply from an inverter. The inverter from Aldi(I had one until it blew up) is not a pure sine wave inverter. If the pc power supply does run I would think it would burn out rather quickly.

I like the idea rmcpb had of using a DSE kit to get the correct voltage. Add a couple of these kits to get the correct voltage. These Regulators are 1AMP, but if the transformer has enough current you can piggy back the regulators to double the current. Be sure to adequately heatsink them though.

[RAJAH235]

FWIW. cj, sorry, but these regulators require at least 2.5 volts or a little more ABOVE the output voltage, to 'safely regulate', (or switch on, so to speak). So By using a 12 volt reg. to regulate a 12 volt battery will not work. The max applied voltage is 35 volts. HTH.. :D L.
ps. Paralleling plug packs is not advisable either due to 'not sharing the load evenly'. One will supply more than the other & o/load...eventually taking the other with it...

[cjmarsh81]

Rajah,
sorry I did not explain properly. I did not mean piggy-backing the plugpacks I meant the regulators. Connect them together and it will double the current.

The 2.5V above the regulated voltage you state is correct. I have however managed to use a 7812 reg on a car battery before and still recieve around 12V. It may not be exactly 12V, but it is better than 14.4 on sensitive equipment. Obviously not ideal.

[astroboy]

I've been down this road myself and sadly gave up and bought the Sbig unit for the ST2000 and an inverter for the ST8i both work well but it smarts to have to pay a couple of hundred for a power supply.
If you have any more luck than me let me know.

Zane

[RAJAH235]

cj, For an easy, safe way to get more current, see previous attachment......A $3/$4 power transistor is all that is required.. :D L.
ps. Still do not recommend paralleling any power supplies or regulators...

[Karls48]

Hi Rogerg

Lot of CCD cameras have input voltage specifications 12V +/-10%. Some will work from 13.8V supplied by lead acid batteries, some will blow up at this voltage. Two easy ways to get portable Power Supply for Astronomical camera is:

1. Get a 12V cordless drill with spare battery and use the battery to power your camera. Those drills use NiCad batteries and fully charged will have about 12.5V and during discharge voltage will remain fairly constant.

2. Get 1.5A Bridge rectifier and connect it to sealed lead acid battery. Pin marked + to your positive on the camera, - to negative and AC pins to the battery – any way around. Regardless which way you connect it to the battery, positive output will be always positive. Big advantage when you connecting camera to the battery in darkness. There is going to be voltage drop across the Bridge rectifier up to 2.8V. With my CCD security camera drawing 300mA, drop out is 1,7V. So from 13.8V battery I’m getting 12.1V output. Difference between input and output will depend on current drawn by the camera and to some extend on Bridge rectifier used.. Less current, smaller voltage drop

Switch mode power supplies (and invertors, and computer PS) are totally unsuitable for use with CCD cameras. It will work, but you are adding noise to your camera output. You spend big money to get camera with 60dB signal to noise ratio and then you connect crap switch mode PS and increase your noise by 30 or more dB.

LM317 or 7812 are not suitable for regulating 13.8V to 12V. Do it and then take oscilloscope and have look on output. You will see why. But LM7805 is fine to get 5V from 13.8V. You will need good heatsink as it will dissipate abut 8W at 1A out.

The best and most expensive solution is regulated Power Supply.

If you want to build regulated PS, use LM2940 low dropout voltage regulator. Only 0.5V difference between input and output needed. 1A output.

Word of caution, all electronic devices will eventually fail. Some sooner and some will take many years to fail. When they fail they will go open circuit (no problem it will just stop working) or short circuit ( big problem if your power supply will put unregulated 16 or more volts to your camera). Good Power Supply will have “over voltage protection”.

I have been working for manufacturer of Power Supplies for security industry for last 15 years. So I got lite bit of experience with PS for CCD cameras.

Hope it will help

Karl