I am trying to simulate a mosquito repellent in Proteus v7.7. It uses an NE555 in astable mode.

My problem is that I cannot hear the buzzer buzzing.

I checked my circuit and everything seems correct to me. Could you please tell me what is wrong?

circuit diagram

setting of buzzer

  • \$\begingroup\$ What's the frequency the 555 outputs? \$\endgroup\$
    – Justme
    Nov 12, 2020 at 11:32
  • \$\begingroup\$ What's your virtual potentiometer set to? If the wiper's set to its resistor's bottom end, you'll get no oscillations. \$\endgroup\$
    – TonyM
    Nov 12, 2020 at 11:40
  • 1
    \$\begingroup\$ first of all, have you made sure you are using the correct buzzer? Proteus has 2 different buzzer models that look exactly the same. One has no simulation model, the other does. You want the one that has the simulation model. Go to the parts list, type "Buzzer" then click on both. Check the schematic model in the top right and see which one has the simulation model \$\endgroup\$
    – MCG
    Nov 12, 2020 at 13:06
  • 1
    \$\begingroup\$ Going by the parameters that you're able to edit for that 'Buzzer' component it looks to me as though it has its own oscillator built in and is intended to be powered by a DC supply. Possibly you should be looking for something like a Piezo Transducer instead. \$\endgroup\$
    – brhans
    Nov 12, 2020 at 16:25
  • \$\begingroup\$ Thank you for your reply. I tried each of the above-mentioned, later I made the operating voltage of the buzzer to 1V and this worked. Thank you all for your time \$\endgroup\$ Nov 12, 2020 at 17:52

1 Answer 1


I have built this circuit in my version of Proteus, and your output of the 555 will only reach 5V output in this circuit. You can double check this by setting your scope to DC and looking at the output. This is likely due to the load the buzzer puts on the output.

Your buzzer is a 12V buzzer. Even if your output was equal to your input voltage of 9V, that's still not enough to drive the buzzer. When you are in the buzzer properties menu, change the operating voltage value to 5V and it'll work.

Alternatively, you could toggle an NMOSFET to switch the buzzer, and attach the gate to the output of the 555, but you need to ensure either a 12V supply, or change the buzzer operating voltage.

Both of these methods I have built myself and they work.

  • \$\begingroup\$ Thank you for your reply \$\endgroup\$ Nov 12, 2020 at 17:49

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