Hi!
I am looking for a product to complete my king rail caller. I need an alarm clock that can play an MP3 file or CD as the alarm tone and DOES NOT SHUT OFF AUTOMATICALLY when the alarm has been going for a certain amount of time. My current Timex model shuts off after 1 hour. This was not included in the product manual. I was hoping that someone might know of one that doesn't shut off (except manually) or would be willing to test their alarm out. I would really, really appreciate the help!
Depending on the alarm clock, you could replace the buzzer with a resistor (silences the buzzer), have the output trigger a flip-flop (causes a permanent change of state), have the flip-flop drive a relay or transistor that powers the player. It will continue playing until you manually reset the flip-flop. Just a block diagram.
Wow! That sounds great but it far beyond my knowledge and skill level. What qualifies the alarm clock to be able to be fixed up like you described? How exactly would one do that? Or where would one find someone that could do that? I'm good with birds but I don't know about rewiring an alarm clock. You've given me hope! Thank you!
If it 's like most battery alarm clocks, the buzzer is just a Piezo element that is driven by a pulsating DC output. The ones I've played with have the Piezo tied between the (+)supply and an open collector transistor or FET. The collector pulls the Piezo to ground at the frequency you hear.
If it 's like most battery alarm clocks, the buzzer is just a Piezo element that is driven by a pulsating DC output. The ones I've played with have the Piezo tied between the (+)supply and an open collector transistor or FET. The collector pulls the Piezo to ground at the frequency you hear.
Well, I've got a conglomeration of fellas who have some knowledge. Maybe some step-by-step instructions that I could show them and see what they think??
2. locate a ground point such as the sleeve of the earphone jack - if it has one.
3. connect the - side of your meter to the gnd point.
4. measure the voltage on both sides of the buzzer (without it buzzing).
5. start the buzzer buzzing and measure the voltages again.
Let me know the results and I'll advise you further.
Note that digital meters take some time to make a measurement, so it may not be possible to measure the pulsing voltage (but try anyway). It depends on how fast the buzzing is and the type of buzzer.
An analogue meter will measure the average voltage due to mechanical inertia.
Do you have any resistors? If not buy say a 1k, 4.7k & 10k.