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I want to make either an alarm clock or countdown timer whose alarm is loud enough to notice, but soft enough to not wake me up when asleep. My idea is to use the sound of an analog clock that I have - powered by a single AA 1.5V battery. I like this sound. So, I'd like to create an alarm or a timer that can turn on the power to this analog clock for a few minutes at least. Ideally, it would be something I could use daily for a couple hours without replacing the timer/alarm battery too often.

I've looked at these programmable relay timers: http://www.amazon.com/dp/B00P0TZ5CY/ but the voltage seems kindof overkill.

I've also considered an arduino board, but I'd like to be able to set the time on the device without plugging it into a computer.

I'm a developer, so I could do arduino programming if needed, but I don't know much about circuitry & hardware. I've also never done an arduino project, so I'm starting from 101.

Any ideas where I could start? The timer I mentioned above would be perfect if it didn't require 12V power. My knowledge is limited, so maybe that's less of a big deal than I think.

  • If I understand your question, you could use a relay to switch the 1.5V supply. – uint128_t Mar 13 '16 at 19:09
  • That's what I'm thinking, but a 12V relay seems like alot. I know it doesn't have to be the same voltage as what it's controlling, but I was wondering if there was something more light-weight. – xdhmoore Mar 13 '16 at 19:31
  • Mainly because I don't want to power it with a car battery and I don't know anything about converting from AC to DC. I guess I could buy a 12V AC->DC adapter... – xdhmoore Mar 13 '16 at 19:33
  • Not all relays are 12V... – uint128_t Mar 13 '16 at 19:43
  • I used to wake up by the relay clicking on inside my stereo, even before the music started. So if you are a light sleeper (which it sounds like), you might not want to use a relay. – Gerben Mar 13 '16 at 20:01
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I suggest a simple setup (similar to my temperature and humidity sensor but less complex).

You can run from 3 x AA batteries, and have an RTC clock to keep track of the time. You can use a MOSFET to turn on your analog clock when required.

The processor can be asleep most of the time, using the watchdog timer to wake up and check the time from the RTC. Don't use an Arduino "board" unless you are running from a wall-wart because the voltage regulator, USB interface, and power LED, will consume too much power.

  • Thanks, that's a great writeup. I'm a beginner with this stuff, so I think that is probably a little more advanced than I'm looking for. It looks like I could just buy the 12V timer relay for less money and plug it in with my wall wart. My only concern is if it would waste too much power. – xdhmoore Mar 13 '16 at 23:18
  • A timer relay won't use much power. – Nick Gammon Mar 13 '16 at 23:42

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