I've build a fairly simple doorbell using Arduino Pro Mini 3.3V: https://www.youtube.com/watch?v=WFd94CYT2Lw&feature=youtu.be
Here's the current setup:
- Arduino running off the 9 V battery
- A simple speaker is connected to Arduino (powered from the battery, Arduino just drives it through a transistor)
- Arduino is reading light level from the light meter every 200 ms.
- Bulb is connected to the wire that is lit up when someone presses the doorbell button.
It works well - someone presses the doorbell button, bulb gets lit up, Arduino notices that (using light meter) and doorbell rings.
In short - battery life. This kind of setup lasts around 2-3 days off a single battery. I was reading all about how to run Arduino off a single battery for a few weeks, even months, but I'm not sure it's feasible in my case. First of all, I need to wake up Arduino every 100-200, maybe 500 milliseconds, to read the light level. Plus, many of those long-battery-life solutions involved basically building own Arduino-compatible scheme from scratch, which I'd like to avoid.
But... I have a 230 V power source - the one that drives the bulb. Issue is that this power source is down all the time, unless someone is pressing the doorbell button.
I could approach it in two ways:
When someone presses the button, I'd power the Arduino and immediately play a song. Issue with that approach is that if someone presses the button for just a split second, my Arduino would be powered up for just that short amount of time, and I wouldn't have enough time to play the complete song.
If I could possibly reverse the way doorbell button works, I could have +230V all the time, and 0 when someone presses the button. This way Arduino would be on all the time, and it would "notice" someone pressed the button when power would go down. Issue with that approach is that song would be played only once guest would release the doorbell button, + the time it takes for an Arduino to boot.
In both #1 and #2, I need two things then:
a) have Arduino on all the time, regardless of whether button is pressed or not
b) power Arduino from the doorbell to avoid having to use a battery
Which kind of means that I need to power Arduino from a dual source - 230 V and rechargeable battery. 230 V when available, and battery when 230 V goes down. In a perfect scenario, this battery would be charged from 230 V source too :)
Any ideas how to built such a thing? Is there some AC power module that I could use? How would I wire things up in such a case - Arduino, AC power module, rechargeable battery?
Or maybe I'm missing some easier, simpler solution here?