Need help building a regulated power supply

[signal15]

I have some security cameras that I'm going to power with a solar panel and backup battery. The cameras require a stable 12v. A car battery/deep cycle puts out anywhere from 12.83V down to 11.5. I built a voltage regular using an LM7812. It works, but it only works when the voltage is 12.5v or higher on the battery. Below that, they output voltage is .5v below battery voltage. My idea is to put something in to raise the voltage to 16v or so, and then feed it into the 7812 (the 7812 can take up to 32 or 35 volts). Does anyone know of a good IC for raising voltage?

Or better yet, a single IC that will do all this internally?

The camera averages 4-6W of power consumption depending on if the IR illuminator is on or not. On boot, it spikes to 9W. So a 12v/1A system would be fine.

 

[apostolakisl]

If you put two batteries in series you would have 24v plus or minus. Of course you would also need a way to charge a 24v setup.

I have to say, however, it surprises me that your cameras are so picky about the voltage. It might be easier to get some new cameras that are more tolerant of a volt or 2 off.

 

[JimS]

A 7812 is not a good choice. You should at least use a "low dropout" regulator but this will still not give 12V out when the battery is at 12V or lower.

To boost the voltage you need a switching supply. Not a trivial design project but you may find an application note design. Circuit layout is critical with switching supplies. There should be chips available to do this with one stage but I don't have any suggestions without doing some looking...

But since you control the supply a 24 V batttery is a good solution. I would still suggest a switching supply to get efficiency or you will be loosing half your energy as heat in the regulator. If you go with a linear regulator you could use 18V (3 x 6V) and be more efficient. Switching converters to drop the voltage should be easier to find.

For switching power supply parts look at National Semiconductor, Maxim IC, Power Integrations, etc...

http://www.maxim-ic.com/app-notes/index.mvp/id/737

 

[signal15]

If you put two batteries in series you would have 24v plus or minus. Of course you would also need a way to charge a 24v setup.

I have to say, however, it surprises me that your cameras are so picky about the voltage. It might be easier to get some new cameras that are more tolerant of a volt or 2 off.

Well, the manufacturer says they are picky and to avoid damage, they should be a stable 12v. They said not to hook them up to a car battery without a regulator. However, in practice, I've found that they actually work down to 9v. The cameras are awesome otherwise, best bang for the buck camera out there. I'm a distributor for them, I'm just trying to get some things finished up and I'll start selling them. I'll give you guys the details when I'm ready, and give a CT discount or do a group buy.

 

[Steve]

I always like to see ingenuity and savings but sometimes I feel its easier and in the long run better and safer to go with a premade UL listed device. In this case have you looked at the Altronix supplies? They have filtered/regulated outputs of 12v and 24v and have all the circuitry for battery backup charging and notification as well as power fail notification. They are solid supplies. I have an AL400ULX and AL600ULX. You can usually find a reasonable one on ebay. Here is a current example for a 2.5A for $59 although I see 400 and 600 often in the sub $50 range. Just another option...

 

[roussell]

Take a look at solar charge controllers. I've used the Morningstar SunSaver series for numerous commercial and industrial solutions and they're perfect for this type of installation. You can get a 6 amp model for around $45-50 bucks.

Terry

 

[signal15]

I always like to see ingenuity and savings but sometimes I feel its easier and in the long run better and safer to go with a premade UL listed device. In this case have you looked at the Altronix supplies? They have filtered/regulated outputs of 12v and 24v and have all the circuitry for battery backup charging and notification as well as power fail notification. They are solid supplies. I have an AL400ULX and AL600ULX. You can usually find a reasonable one on ebay. Here is a current example for a 2.5A for $59 although I see 400 and 600 often in the sub $50 range. Just another option...

The charge controller I'm looking at has a battery output on it with a low voltage cutoff. But it outputs whatever the battery voltage is, it's not regulated. I found this though:

http://www.current-logic.com/shop/index.ph...;products_id=39

I could use it in conjunction with the charge controller to get my stable 12v output.

 

[KeepItSimpleStupid]

The 7812 series is a poor choice. You need a 3V differential for it to work. www.national.com has products and evaluation boards for switching regulators. There is also software on the site to design your own and receive a kit of parts. 12V switching regulators are commonplace. www.jameco.com should have some.

 

[signal15]

I think I'm going to get the one I posted above. It's only $25. Maybe I'll cut it open and see how it's made. It's not a priority right now because I had my buddy come over with his mole and we ran a conduit under the street after it got dark.

 

[dem5867]

Vicor,, If I remenber correctly they make a 12vdc to 12vdc converter (Not cheap I'm guessing $150.00us if not greater.).. Any how I think you will find the input spec.s to be a good range ,, I'm betting 10vdc or less on the low end and at least 15 plus on the high end. Very low loss also... The bad is you appear to only need 12 watts or less and there small ones used to be 50 or 100 last time I looked.