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Step 8Find Your Triggering Signal
**Use caution when working on open electronics like this**
For our circuit to work we need a 5v signal that will appear when the clock radio's alarm goes off. This can be tricky because (as in my case) there may be no schematic available anywhere.
First I had to find the clock's microcontroller as that would have some output lines to turn the speaker on. This was pretty easy on my clock as it only had 2 ICs. The writing on the chip was faded so I had to guess what pin to use as the trigger.
I did this by first powering up the clock with no alarm set, and then (being careful not to short out anything) use a multimeter to measure the pins of the chip. In my case there was quite a few pins that were at 0v.
Then I set the alarm to go off and remeasured each pin. Some of the pins that measured 0v previously now read 5v. Hooray!
For our circuit to work we need a 5v signal that will appear when the clock radio's alarm goes off. This can be tricky because (as in my case) there may be no schematic available anywhere.
First I had to find the clock's microcontroller as that would have some output lines to turn the speaker on. This was pretty easy on my clock as it only had 2 ICs. The writing on the chip was faded so I had to guess what pin to use as the trigger.
I did this by first powering up the clock with no alarm set, and then (being careful not to short out anything) use a multimeter to measure the pins of the chip. In my case there was quite a few pins that were at 0v.
Then I set the alarm to go off and remeasured each pin. Some of the pins that measured 0v previously now read 5v. Hooray!
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