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This is an add-on amplifier and speakers I've installed in the hourly chiming cuckoo clock and attached clock speaker output as an input source to PAM8403.

Simple PAM8403 Audio Amplifier Circuit

Source: Circuits DIY - Simple PAM8403 Audio Amplifier Circuit

All is working great with quality sound, the only issue is with a power consumption of PAM8403 as after hourly chime there is no audio to play around the hour and 3 AA D size batteries power this circuit and that last longs around 80 hours only.

So my question is how can I cut-off the power supply to this circuit when no audio is playing, and turn it ON when audio starts at hourly chime which plays cuckoo strikes and some music for around 30 seconds?

PAM8403 2 x 3W Amplifier Board
Source: Amazon - CentloT - PAM8403 2 x 3W Amplifier Board

Stereo Audio Amplifier - PAM8403
Source: Sunrom Electronics - Stereo Audio Amplifier - PAM8403

PAM8403 pinout from datasheet
Source: Mouser - Diodes Inc. PAM8403 datasheet

Clock PCB 1
Clock PCB 1

Clock PCB 2
Clock PCB 2

Clock PCB 3
Clock PCB 3

CLock PCB 4 Clock PCB 4

Clock PCB 5 Clock PCB 5

Clock PCB 5 - With Details Clock PCB 5 - With Details

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    \$\begingroup\$ The easiest way to turn this amplifier off (i.e. supply current <= 1uA) is to drive the SHDN input low. Though whatever timing circuit you use to do this will consume some power. \$\endgroup\$
    – Finbarr
    Commented Apr 17 at 10:45
  • \$\begingroup\$ Can you please elaborate on how I can connect the SHDN? The circuit I have is the right-side one which doesn't have the SHDN pin connection \$\endgroup\$ Commented Apr 17 at 10:55
  • \$\begingroup\$ You may have to connect directly to the pin on the chip then. \$\endgroup\$
    – Finbarr
    Commented Apr 17 at 10:59
  • \$\begingroup\$ Thanks for the insides, added 2 snaps of board and schematic which looks like SHDN is connected to PVDD to maximize the outputs \$\endgroup\$ Commented Apr 17 at 11:08
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    \$\begingroup\$ @NayanPanchal - Hi, (a) You said that you added "Clock Schematics" but those were photos of a PCB (presumably the clock's PCB), not schematics. || Unfortunately reflected light on the PCB prevents reading some connector labels. That is where you could start to reverse-engineer the PCB to recreate partial schematics, looking for signals related to when the hourly chimes are played. \$\endgroup\$
    – SamGibson
    Commented Apr 22 at 16:06

1 Answer 1

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How to trigger the PAM8403 audio amplifier module when the clock chimes

There are many details still unknown at this stage, but here are a few suggestions to help you - depending on exactly which approach you want (or are able) to take. This is a braindump and is not intended to be a complete step-by-step solution.

General Notes

  • As already commented, to reduce the power consumption of the PAM8403 when it's unused (i.e. for 59 minutes of each hour, if I understand correctly) your choice is either to remove its power supply (e.g. by controlling a P-channel MOSFET in its supply rail) or to pull its –SHDN pin low, during that time.

    However, you should not have the PAM8403 audio input from the clock active (i.e. greater than +/- 0.3 V, see the datasheet Absolute Maximum Ratings) when the IC has its power removed. If you aren't sure you can comply with that, then using the –SHDN input to disable the IC for each 59 minutes is the better option.

  • The PAM8403 datasheet that you kindly linked, doesn't include a specification for the time between power-on and normal operation, or between coming out of shutdown and normal operation. That means any delay that the IC requires in order to become ready, is within its specification (as there is no specification for that parameter). You may want to test both power control options and see which method of reducing the power consumption has an acceptable time-to-ready value for you. You might miss the beginning of the hourly chimes, if the IC takes longer than you want before it starts amplifying the audio.

  • From your photos, it seem your pre-built PAM8403 module has not made the –SHDN signal available on an easily-accessible terminal for you. Therefore you will need to decide if the soldering and PCB track cutting required to detach that pin from PVDD and make it available (e.g. via a mod wire tacked to the PCB) is something you can do.

How to enable the PAM8403 when the hourly chimes sound

I can think of 3 basic approaches (of course there are options within each one):

  1. Investigate using a pre-built "clap detector" module (or build your own), with its own microphone & placed close to the chime's own speaker, to detect the sound & generate a digital output when sound is detected. Use that module's output to drive a monostable set to (for example) 1 minute. Have the monostable output drive whichever method of powering-down the PAM8403 you have chosen (e.g. using the –SHDN input). Depending on exact component choices and signal polarities of the clap detector & monostable, a simple BJT or MOSFET inverter may be needed to drive –SHDN high when you want the amplifier to be active.

    One example of a problem with this approach is that the amplifier might be enabled by any sufficiently loud sound in that area, not only by the chimes from the clock.

or

  1. Connect directly to an audio output from the clock, via a variable attenuator, rectifier (if the audio input signal can go negative relative to the comparator's ground rail), comparator, and then again, take the digital output of the comparator into a monostable whose output enables the amplifier.

or

  1. Look for a digital signal on the clock's PCB which changes state at the start of the hourly chime e.g. if one of the bird in/out or up/down signals that you labeled on a recent image changes state at the start of the hourly chime that you want to amplify (or even slightly before the chime starts), then use that signal (after any necessary conditioning / level translation etc.) to trigger the 1 minute monostable. Then use the monostable's output to enable the amplifier, using one of the options mentioned before.
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  • \$\begingroup\$ Yes definitely was thought the same to add microphone controller but as the clock is installed in living room and it contains big output soundbar and other noises, so that is not feasible to have it, but the monostable option we can look forward, Yes Bird In/Out may work as trigger and labeled Swing Dancers may also work as trigger to 555ic Monostable, my quick question would be using speaker output as a trigger to 555ic? \$\endgroup\$ Commented Apr 24 at 9:20
  • \$\begingroup\$ When we connect LED to monostable with 555ic it glows but my question is if we power that 555ic with 3 AA D size batteries will it work and if we replace LED with PAM8403 power input will it work?, I know it's try and error exercise but asked if you have tried before or have some insights. \$\endgroup\$ Commented Apr 24 at 9:26
  • \$\begingroup\$ Hey I would be fine with any other amplifier as well which automatically shuts when there is no input signal or any other power efficient amplifier to play hourly chims in additional 8ohm 1w (2 speakers) and can be powered by 2 or 3 AA D size batteries or even with 9v HW (Hi-Watt) battery if it last longs for 2-3 months, so we can remove PAM8403 add-on, the amplifier should be loud only there is no bass to play just a bird chims and dancing music 😉 \$\endgroup\$ Commented Apr 24 at 10:31
  • \$\begingroup\$ I'm fine with any pre-built or to build with Schematics, even we can have 2 mono power efficient amplifier as well... \$\endgroup\$ Commented Apr 24 at 10:34
  • \$\begingroup\$ @NayanPanchal - "the clock is installed in living room and it contains big output soundbar and other noises" This is new information, so I wasted my time explaining option 1 for the reason you explained. || "using speaker output as a trigger to 555ic?" You cannot use the speaker output directly in that way. I explained the circuit blocks I consider would be needed, in option 2. || "3 AA D size batteries" That's confusing. There are AA size batteries (really cells). There are D size batteries. I don't know what you mean by "AA D size batteries", although this doesn't change my replies. \$\endgroup\$
    – SamGibson
    Commented Apr 24 at 15:53

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