This is often achieved with a simple two-lead inductor. My Vin is a square wave at whatever frequency and duty cicle are needed (the resonant frequency of the buzzer is 6.5kHz so I guess that's the best choice), how can I broadly calculate the values of the autotransformer? Could the stepped-up voltage given by the inductor damage the source power? Would be better to put a diode before the Vcc? Say that my Vcc is 2.5V and I want todrive the buzzer with 25V (so x10). The goal is to understand what's going on there, eventually understand how to dimension it, and find a couple of those for try this way.Įdit: After the answer, I understood that the mysterious component is an autotransformer, is it correct to say that it's like a transformer with two pins connected? If it is correct, the circuit I saw should be one of the three cases forward, possible? Which one could it be? Other suggestions about how to make the buzzer louder?.because I don't know what to search for and, eventually, how to dimension it. I managed find that component only on alibaba/aliexpress, possibly I can't find it on RS-Components/Farnell/Mouser/etc.Why does it make the buzzer make so much more noise with it (also the circuit that I saw the component on works at 3V, like mine, so no difference there)?.What is that component that seems (based on the name) specifically made for this purpose?. ![]() ![]() I found the component on alibaba/aliexpress from China, and there it's always called something like "alarm boost three pin inductor" (if you try to search on alibaba those exact words you'll find a lot of them). Also I would say that in this circuit I actually don't know what Vin is (square wave or something else). Where two pins are connected as R2, and the third (don't know which of the three) is connected to Vcc.Įdit: I've inserted the circuit because the previous sentence was not correct/clear. I started googling and I'm pretty sure the part is this, connected as in this figure: I opened it and I realized that was using a buzzer very similar (bigger in radius which makes it work at a different frequency, but that's not the point) and a circuit very similar to the one posted above, but instead of R2 there's an inductor-like thing. While I was searching, I took a look at a small device I had at home which makes a loud noise. I suppose it would work, but finding something simpler would be better. Another option is to insert in the board a circuit to step-up the supply of that part. One option is to use an H bridge for doubling up the peak to peak voltage, but since the starting voltage is low, the buzzer will be louder but not as much as I wish. Since the piezo is basically like a capacitor, putting an inductor instead of R2 makes a resonator and makes it louder, but since my power supply is very low compared with the 30V maximum of the buzzer, that's still too little. Since the maximum peak to peak voltage in the datasheet is 30V I tried to use a 25V source (only for the BJT circuit, not the digital part), and in fact it becomes significatly louder, so basically the goal is to step-up the voltage around the buzzer. I'm already feeding the BJT with a PWM with duty cycle 50% around the resonant frequency of the buzzer, so I can't do better about the frequency. I know that I need to drive it with a waveform because it doesn't have the driver circuit and all the stuff, so I started using the circuit on the right, which worked, but was not very loud, so I started document how to make it louder. Now I've changed the board and its case, and I need to change the buzzer to a piezo one of this kind: I've already successfully used an active buzzer (with build-in driver oscillator) drived by an NPN transistor in on-off, and it worked fine. ![]() I have a small circuit working on 2xAA batteries (3V) with an MCU and a buzzer for alarm sound.
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