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I'm fairly new to the world of electronic design. I'm building an astable 555 timer with the limitation being I can only drive it with a 3v coin cell battery (design has to be lightweight). I've been experimenting with different buzzers in search of a very loud one. The buzzer I am utilizing is 3v - 7v range. I am assuming the capacitors and resistors are reducing the voltage the buzzers sees in this circuit? Is there a simple approach to boosting the voltage? Or is this a current problem? Or both? I can achieve my desired dB with double the voltage on my power supply with this circuit. Same dB level applying the voltage directly to the buzzer. Thanks!

Credit: Jason Poel Smith, instructables.com https://imgur.com/a/4gv3pIF Ref: Jason Poel Smith, instructables.com

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    \$\begingroup\$ No, the resistors have nothing to do with the output voltage. The only ways to boost it are to either increase the supply voltage, or use a step-up transformer on the output signal. \$\endgroup\$
    – Dave Tweed
    Nov 10, 2023 at 18:15
  • \$\begingroup\$ You can't get much out of a coin cell. Is there any chance of using two in series? \$\endgroup\$ Nov 10, 2023 at 18:26
  • \$\begingroup\$ I don't know if that's what you are doing with 555, but the loudness peaks when the buzzer is driven with its resonance frequency. Ignore this comment if you are using a buzzer module instead of piezo buzzer element. \$\endgroup\$ Nov 10, 2023 at 18:35
  • \$\begingroup\$ Eric D - Hi, Please note the site rule which requires that if a post copies or adapts content (e.g. text, image, photo etc.) from elsewhere, that content must be correctly referenced. As a minimum, for online material, the original source webpage / PDF / video etc. should be named & linked (see that rule regarding references for books / articles etc.). Therefore please edit your question to add the original schematic image source name & link (and please remember it's your responsibility to do that in future). Thanks. (Please see the tour & help center for the main rules.) \$\endgroup\$
    – SamGibson
    Nov 10, 2023 at 18:57
  • \$\begingroup\$ Using a 100K resistor and a 2uF cap would waste less energy from the coin cell and perhaps let more voltage for the buzzer. \$\endgroup\$
    – Fredled
    Nov 10, 2023 at 20:59

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The circuit with the 555 cannot apply more voltage than the power supply to the piezo buzzer. So it will be less loud than if you connect it directly across the battery.

The circuit you show would provide a brief beep (maybe 150ms) every 8 seconds or so. The time may be too short for the module to get up to full volume, and there will be some voltage drop in the 555 output. An NE555 is not recommended for operation below 4.5V, but there are other variations such as TLC555 that are happy with 3V (and draw a lot less current so would be more appropriate for a coin cell).

To get more loudness, I suggest a TLC555 or similar and operation from 2x 3V cells in series.

If your beeper is actually an electromagnetic type rather than piezo, the current may be too high for a coin cell, given the internal resistance of the latter.

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  • \$\begingroup\$ Good catch. I feel silly not thinking about the voltage range of the 555 timer. Do you think I could get away with a TLC555 and a single 3V coin cell battery? Testing my piezo on the power supply even down to 2V is loud enough. I am not sure what the piezo is getting exactly for voltage in the 555 timer circuit, but I did try to read with with my multimeter and each beep was around 2.75V. Would this indicate it's not enough current getting through due to the voltage rating limitation of the NE555? \$\endgroup\$
    – Eric D
    Nov 10, 2023 at 20:01
  • \$\begingroup\$ The TLC555 works down to 2V if memory serves, but the output drop will be more for a given current at low voltage. You can look at the datasheet once you measure the current your beeper draws. \$\endgroup\$ Nov 10, 2023 at 20:05
  • \$\begingroup\$ To boost the voltage for your buzzer, you can use an NPN transistor like the 2N3904. \$\endgroup\$
    – liaifat85
    Nov 10, 2023 at 21:16

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