Good day folks. Recently someone suggested that I'd install an alarm system in my apartment and my brain instantly sprung into action and began devising plans for making one rather than buying an off the shelf unit. It's a lot cheaper for one thing and secondly nothing beats a good DIY project The brains will be an Arduino of course and the system itself would be relatively easy to implement....DAMN easy in fact: just a couple of IFs to monitor some switches...that's not important.
What IS important is that we want this thing to run even when the power goes out so we need some sort of battery backup. Of course I could just plug the adapter that powers the whole system into an UPS, but it seems too "simple" for my taste I was thinking of making my own battery backup system with one (or more) UPS batteries. The operation would be fairly straightforward: run on battery when mains is not present, switch to mains and charge battery when it comes back...The switching can be something as simple as a relay (which I did in the past for a different project), it's the charging that's going to be the most challenging so as not to kill the battery.
I was thinking of something very basic like an adapter simply hooked up to the battery. The label says "charge at constant voltage" and there's some values on the battery usually 13-14v, so I was thinking what if I just apply 13v straight to the battery ? I've seen plenty of battery charging circuits online, most of them involving an LM317 in some fashion but to keep it as simple and dirty as possible, I thought of the above method....it would probably become an issue if the battery is drained and the charge current is too great. Seeing how I'll have an arduino as the brains, I can have it interact with the battery as well to start/stop charging when certain values are reached. Any ideas on this battery backup portion ? It could even be a generic application for other projects, not just an alarm system.
What IS important is that we want this thing to run even when the power goes out so we need some sort of battery backup. Of course I could just plug the adapter that powers the whole system into an UPS, but it seems too "simple" for my taste I was thinking of making my own battery backup system with one (or more) UPS batteries. The operation would be fairly straightforward: run on battery when mains is not present, switch to mains and charge battery when it comes back...The switching can be something as simple as a relay (which I did in the past for a different project), it's the charging that's going to be the most challenging so as not to kill the battery.
I was thinking of something very basic like an adapter simply hooked up to the battery. The label says "charge at constant voltage" and there's some values on the battery usually 13-14v, so I was thinking what if I just apply 13v straight to the battery ? I've seen plenty of battery charging circuits online, most of them involving an LM317 in some fashion but to keep it as simple and dirty as possible, I thought of the above method....it would probably become an issue if the battery is drained and the charge current is too great. Seeing how I'll have an arduino as the brains, I can have it interact with the battery as well to start/stop charging when certain values are reached. Any ideas on this battery backup portion ? It could even be a generic application for other projects, not just an alarm system.
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