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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
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