3.3v - 6v Camera with 12v battery

[hillmanant]

Hello Techies

Thanks for your help in advance.

I am a electronics tinckerer and a diehard fisherman, I was looking to build my own underwater camera for ice fishing this year because all the retail ones are too expensive and don't have the photo quality I could build.

So heres the setup
The casing will be made out of plexiglass tube welded with weld-on 3 to a piece of 3/16 plexi on either end and a micro HD CCTV camera encased in there along with 6-8 leds and a tether to topside and the power and screen. Now I am looking to power this with a standard Vexilar 12v 7Ah battery. This is the spec sheet that came with the camera. One thing I don't understand here is it says 3.3 - 6v but came with a 12v wall wort power suppy, now I realize this has to do with unregulated and regulated whereas I will be hooking it stait to a 12v battery which would be not unlike hooking it to a regulated power supply at 12v not falling off during draw.

Now my question how do I run this camera without damaging it with a 12v deep cell battery? What resistors and such would I need to put in series with the supply line to make it not fry the camera? How long would the battery last?

Also I have a 7" Color TFT LCD Car Rearview Monitor for DVD Camera VCR that I bought off ebay here and it says it consumes around 8W how long would the battery last powering both the screen and the camera?

 

[(*steve*)]

OK, a number of things here:

1) avoid flat surfaces. Most camera housings have convex surfaces to help prevent them from imploding.

2) consider very carefully how you will seal it.

3) Can you connect the 12V to the charger socket? That sounds the safest thing to do.

Beware that if you get water in your housing you are likely to do a lot of damage. If that housing contains a lead acid battery, the likelihood is a lot higher.

Try your enclosure out with a brick in place of the battery (for example) and a dummy camera. Take it down a few times like this, remembering to open and close it one the surface each time. See how it performs and determine the depth at which it leaks or implodes.

Then figure out a safe depth (perhaps half the failure depth?) before you insert the real equipment.

8W will run from a 12V Z amp-hour battery for up to 1.5*Z hours (so about 10 hours from a 7 amp-hour battery). This assumes 100% efficiency from a switchmode regulator, which is not acheivable (but high 80's% is).

 

[hillmanant]

OK, a number of things here:

1) avoid flat surfaces. Most camera housings have convex surfaces to help prevent them from imploding.

2) consider very carefully how you will seal it.

3) Can you connect the 12V to the charger socket? That sounds the safest thing to do.



8W will run from a 12V Z amp-hour battery for up to 1.5*Z hours (so about 10 hours from a 7 amp-hour battery). This assumes 100% efficiency from a switchmode regulator, which is not acheivable (but high 80's% is).

Thanks for the info Steve

I didn't explain myself clearly the camera is remote, on the end of a tether in a casing. There is no power in the casing, it is connected on top of the ice. only thing in the casing is the camera lens and the leds.

I do like the idea of avoiding flat surfaces but I am only putting 25 feet of cable on it so that is the deepest I will be able to go, @ 25 feet there is 10.84 psi and plexi is more than capable of this. I am solvent welding all the joints except the hole for the cable that will be epoxy resin sealed, submerging it and then putting the camera in is not an option.

The info on the aprox down time is appreciated.

I still don't understand why it comes with a 12v power supply yet is says it needs 3.3-6V?

 

[(*steve*)]

The batteries require a higher voltage to charge them. The manufacturer has decided that a 12V charger is the one it will use. Inside the camera there is circuitry to manage the charging process from the provided charger.

Technically, they probably have a switchmode regulator and a charge management device. The exact working of these is probably not relevant.

As before, my advce is to keep the batteries installed and wire power to the charger if the unit will operate in this manner. It is a good solution because short interruptions to the power are not going to affect the device.

If you want to remove the batteries and replace them with external power, you have a larger job on your hands. Is that what you want to do?