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From Mini Speaker To high db Piezo buzzer Alerting Device


New Member
Thread starter #1
I need some advice on what is the quickest way to change the alert signal output through a amplifier to run a fixed tone transducer with on board tone driver ? Problem to start with is my customer has issues of the speaker alerting device on this agricultural implement monitor is too quiet . So I suggested taking the signal output through an higher power transistor and having some caps to filter the Tone hz pulsed as it would then pulse the Piezo buzzer on/Off @1hz as the speaker did previously but just high db. The existing driver on pcb is a 20ma npn transistor pulled low at the gate . What would your suggestions be ????


Well-Known Member
Not a bad plan, but needs more information. What power supply voltages are available for the beeper? How much room is available for the beeper? Have you listened to a few of them to decide which model is loud enough?



Well-Known Member
taking the signal output
Getting closer. What is the "signal output"? Amplitude, shape, frequency, DC offset? Can you post a partial schematic showing the speaker, connections, and the circuit driving the speaker?

There are several ways this can go. The most simple will have a certain characteristic to the sound. How "crisp" do the beeps have to be? If you take the speaker amplifier output, rectify it and filter it to produce a DC voltage that varies as the envelope of the tone burst, that voltage will not rise or fall very quickly. The beeper will start up fast enough, but when turning off the tone will trail off more like the end of hitting a chime. As it trails off and gets softer, the pitch will increase slightly. It is a low-cost approximation of a chime. I put this circuit in a bunch of ambulances way back, and the same thing is the warning chime in my clothes dryer. To see what I'm describing, put a 1000 uF capacitor in *parallel* with the beeper and listen to the sound when you disconnect it from a +12 V power source.



Well-Known Member
Most Helpful Member
The PUI piezo beeper produces 115dB at a very small distance of 10cm (4"). Of course its loudness reduces at a distance. How much distance and how much loudness do you want?
A higher supply voltage for the transistor driving the beeper will increase the current and increase the power output and make it louder but its maximum allowed voltage is only 13V.
I think a higher frequency piezo beeper can be louder but old people without hearing aids cannot hear the higher frequency.

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