Re: Dual power source
I only need 2 of these circuits; one for the house and one for the garage. Both alarms are independant with sirens but both will communicate status to each other making it difficult to disable both at the same time.
1. I was planning on using a wall adapter trickle charger. I figured it wasn't worth reinventing the wheel when I can buy one for $29.95 locally; gut the circuits and place it in a metal shield within the alarm box.
http://www.rpelectronics.com/fc-612c...ger-6-12v.html
2. My 12V 7Ah battery is at 13V right now and it has been sitting on the shelf for at least a month since last charge. I took readings on first charge and initial charging was at 13.5V, intermediate was at 14.25V and trickle was at 14.5V (using 200mA setting). That could potentially place the battery voltage higher than mains side when trickling.
3. I looked at my old DSC1000 alarm circuit and it doesn't seem to use 2 diodes to switch sources; the circuitry seems more complex (18V from transformer in mains breaker box enters at bottom left). Same with the more advanced circuits on google. If 2 diodes would be good enough, I would think it would be common usage; less parts = more revenue. They have at least one IRFZ22 N-CH HEXFET (bottom left) and a LM317 regulator (on heat sink) and a 7805 at top left.
4. I can afford the HEXFETs, I already have some on hand and really like the "no doubt about it factor"; either it was ON or OFF regardless of voltage when controlled properly and have built-in shottkeys, switch fast enough and are rated for much more current and voltage than I will use.
Mains voltage ON opens mains N-CH HEXFET and shuts battery P-CH HEXFET.
Mains voltage OFF shuts mains N-CH HEXFET and opens battery P-CH HEXFET.
The concept seemed simple to me when I first thought of it, and then I became unsure the more I googled. I'm just not sure on the resistors and exact setup, should I also have caps in there? The googles I found were vague on some aspects, and not all of them were the same.
Robert
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