Hello All!

This is my first post-- I am a beginning electronics hobbyist, and I have successfully built a metronome (we have uploaded the schematic) for my son-- it works well, but we have trouble hearing the "click" over our noisy scales. What can we do to increase the volume of this project?

Thank you,

Louis

 

Can't see the image. It is too small.

 

You could use a 1000 uF capacitor and increase the voltage. The 555 can take 18 volts if I remember correctly. Check the datasheet for your specific chip and manufacturer.

 

Your problem is not loudness. You need an additional oscillator to extend the duration of the sound on the speaker.
The 555 timer sends out a transition, not a tone.

 

Can't see the image. It is too small.

Sorry about that, try this one--

 

Sorry about that, try this one--

You should use two 555 timers, one to set the beat, (95% duty cycle) and a second one with a tone that plays for the 5% that the first one is on (e.g. 1000 Hz). Then bring the two together with something like this...
A transistor AND gate with two PNP transistors.

Use a 555 online calculator to hit the desired combo. PNPs work better because the 555 circuit gets more complicated to get duty cycle below 50% to use NPN transistors.

 

Here is an option for the beat metronome, use a log (audio) potentiometer for the 500k resistor (connected across left and middle pot terminals when terminals are below the knob).

 

Since all you want for a metronome sound is a tick, not a keyed beep, you can get there with a single 555. And because you just want a sharp tick, you don't need a coupling capacitor. Try this.

Rework the 555 for a fixed pulse width and variable frequency. In your schematic, the 1K becomes a 100K pot and the 250K pot becomes a 6.8K fixed resistor. The speaker ties directly from pin 3 to the +9V. The 555 output will spend most of its time very near the +9V, then dive down close to GND for the tick sound. The tick pulse will be about 0.1 sec, long enough to be heard but short enough that the 555 output stage doesn't fry trying to drive 8 ohms.

The lowest rate is about 30 ticks.min. If you put a 1K fixed resistor in series with the pot, it limits the upper rate to 240 ticks/min. Both of these extremes are greater than a standard metronome (40 to 208 bpm). Making the fixed pulse width longer (by increasing the 6.8K resistor) might make the output louder, but you also might hear a second tick on the trailing edge of the pulse. Experiment.

Also, depending on the exact type of 555, the speaker might produce an inductive kick on the trailing edge of the pulse. Add a diode in parallel with the speaker, something like a 1N4002, cathode to +9V, anode to pin 3.

And of course, if this is too loud you can put a fixed resistor in series with the speaker.

ak

 

I've done this with just a, "tick" for a person practicing to be a court stenographer. My cure was to use an earphone. Cheating? Probably.

Anyway, it can be done. You're just working on loudness.