New to the community and less than a hobbyist so please advise if this question should go elsewhere.

I am not noting a particular alarm clock or model because I would like this to be repeatable across any/most generic store-bought types of digital alarm clock.

What I'd like is to have the user set the alarm clock as they normally would and when it 'rings' I need some form of an output. This should be either some sort of voltage (nothing high or high amp, 5 or 12v and 100 or 200ma should be plenty) or perhaps just a contact closure.

This would then be taken to a home control system to perform whatever tasks are wanted for wake up and so that is why the question is in generic terms.

Can this be achieved in a way that can be generically applied to most alarm clocks and if so how? (in somewhat noobish terms if possible)


If you can tolerate having the buzzer/speaker still sound when the alarm goes off, then you could attach a microphone to the side of the case, and then you wouldn't have to open up the case at all.

Use a circuit something like the one below to convert the output of the microphone (fed into the Audio input line here) into a digital signal at the output of the comparator.

enter image description here

The circuit doesn't specify a comparator, but one you could look at is the LM311. It can sink 50 mA, which would make it ideal for driving a relay.

  • \$\begingroup\$ Thanks, that's an interesting approach. What would keep the mic from picking up voices and triggering as well? Alternately could the audio input be taken directly from the speaker's terminals?(in the case of a clock radio, else from the buzzer) \$\endgroup\$ – JoelAZ Jan 13 '15 at 2:37
  • \$\begingroup\$ @JoelAZ That's the reason for the comparator -- you can adjust the resistors to vary the threshold of the sound needed to trip the output. Mounting the microphone very close to the buzzer or speaker should provide enough difference in amplitude to distinguish between the alarm going off and the ambient noise. Yes, you could also feed this circuit from a speaker of buzzer source. The comparator would then function to distinguish between an alarm and any noise in the output. \$\endgroup\$ – tcrosley Jan 13 '15 at 3:54
  • \$\begingroup\$ interesting thank you. Now I just need to figure out the actual connections (ie. how to read that wiring diagram - am not an EE student or even hobbyist.) \$\endgroup\$ – JoelAZ Jan 13 '15 at 3:58

Any alarm clock that uses a buzzer or a speaker will have access to the signal there. The connection might be wires, or it might be soldered right onto the PCB.

(So far as I know they have not integrated speakers onto an IC)

You will have to take some measurements of the signal.

  • Is it DC and at at least 0.8V? Then you could boost the current with a transistor and connect it to a relay.
  • If it's AC you might want to add a diode to rectify, an RC low pass filter, then proceed as with the DC case.

The bigger question is this: "What home automation system does not already have a clock?"

  • \$\begingroup\$ The automation system HAS clocks of course. The issue I'm wanting to address is the user interface - rather than force them to use a touch panel or whatever, some people just like their alarm clock. Rather than make them set the alarm in two places or make them give up the bedside clock, using the clock to trigger the events is the "best of both worlds" solution. Also, some actually want/need the clock to wake them up. The events we trigger could be periphery actions (turn on towel warmer, slowly ramp lights, etc.) but not actually wake them up. \$\endgroup\$ – JoelAZ Jan 12 '15 at 19:55
  • \$\begingroup\$ As far as DC and or AC, not sure as this could change. Thanks for both answers. Would either one apply for a clock radio type alarm? I.e. would there still be a constant/trigger voltage somewhere or would it just be the speaker output? In which case, could/how would I utilize that? \$\endgroup\$ – JoelAZ Jan 12 '15 at 19:57
  • \$\begingroup\$ OK. So, after looking up the terms transistor, diode, RC low pass filter I understand the overall concepts better. ty. Could you offer a bit more help in the way of specs/selection of a transistor? (I went to digikey and the choices are dizzying, not to mention meaningless to me.) Similarly can you offer specs for the diode and low pass filter (at least what cutoff frequency I'm targeting)? I appreciate the help. As originally stated, I'm less than a hobbyist at this. Just the two lines you wrote have me working to wrap my head around it. Thanks much! \$\endgroup\$ – JoelAZ Jan 12 '15 at 21:49

An output common to all alarm clocks should be the buzzer. This could be used as a signal to activate whatever you want with the right circuitry. A quick google search provided this article http://www.todayifoundout.com/index.php/2010/06/how-to-hack-an-alarm-clock/

  • \$\begingroup\$ Thanks. Not sure if buzzer is common to ALL but definitely many. What about a clock radio (speaker output)? Also, I checked that link and it seems a bit over my head, using a microcontroller, etc. Any examples of a simpler implementation? What search terms did you use to find that? \$\endgroup\$ – JoelAZ Jan 12 '15 at 19:59

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