Power Supply for in wall and outside use.

[Construction Solutions]

I am developing a new product that will be used primarily for residential use. I'm trying not to disclose the entire scope of the project until the patent is recorded, so please forgive the secrecy. I need a Class 2, 120v AC input, 12v DC (13.4v?) output power supply. The power supply will be in a small control box with room for a back-up battery. When our product is installed in new construction the power supply will likely be installed in an exterior wall, accessed from one side by an access panel. From there there will be a wire run, likely less than 20' to the device it powers. For retrofit to an existing home, the power supply will likely be mounted outside in a weatherproof box with an undetermined, but hopefully short, run to the device it powers. There will be venting in both cases of installation.

The device being fed uses <1000ma. There will be a I think installers of the product will likely use a 4ah lead acid back-up battery. I think this can kept charged with as little as 300ma? I prefer to not use a wound or cordial style transformer and rectifier. I think my voltage and amperage needs are small enough to use a power supply similar to what a laptop uses - sorry don't know the term.

My questions are: can I use that style of power supply both in wall, indoors and outdoors in a weatherproof box? Will it supply the device and provide a charge to the battery? If so, will I need to control the length of time and amount of current to the battery? Is it a simple splice coming out of the power supply to feed the device and charge the battery?

Thanks,

Shane

 

[tom baker]

this is more of a UL listing question than an NEC one. Your product may need to be listed by a NRTL, so I would start with that part of the design. the NEC may apply to the wiring to your box and any load side wiring.

 

[Rampage_Rick]

The device being fed uses <1000ma. There will be a I think installers of the product will likely use a 4ah lead acid back-up battery. I think this can kept charged with as little as 300ma? I prefer to not use a wound or cordial style transformer and rectifier. I think my voltage and amperage needs are small enough to use a power supply similar to what a laptop uses - sorry don't know the term.

My questions are: can I use that style of power supply both in wall, indoors and outdoors in a weatherproof box? Will it supply the device and provide a charge to the battery? If so, will I need to control the length of time and amount of current to the battery? Is it a simple splice coming out of the power supply to feed the device and charge the battery?

Thanks,

Shane

I don't see any reason why you couldn't use a switched-mode power supply in those locations. SMPS are commonly used to supply 24VDC for industrial controls. You might run into issues with the SLA battery. They're somewhat picky about voltage if you're hoping to get any reasonable lifespan. You may want to investigate some of the products available for alarm systems or CCTV.

 

[dfmischler]

Sounds like you need to learn about modern battery management. There are tons of products out there these days, including integrated circuits you would use on your own boards, and modules you would wire in to your unit. Of course, the people who build this stuff publish lots of info to try to convince you that their solutions are best. But you can learn a lot from their propaganda, anyway.

examples (no endorsement implied, and any search engine will find many more):

Astrosyn Guide to Battery Management

Linear Technology Battery Charging and Management Solutions

TI Battery Management Guide

Another issue you will need to resolve will be meeting the environmental requirements of whatever you build once you bolt it to the outside of a house. Think of how cold it will get on a winter night in Minnesota vs how hot it will be on the sunny side of a house on the hottest day of the year in Phoenix, AZ. This is not really as easy as it sounds for something that contains electronics and batteries.

 

[hbiss]

You may want to investigate some of the products available for alarm systems or CCTV.

Yeah, really. Forget the patents and secrecy- it's already been done. But as has been said, you are going to have to consider the environment (mainly temperature) if using lead-acid batteries for backup. Why does this have to be located outside?

-Hal