I'm an amateur so this is a basic question.

I have a 555 in astable mode producing a frequency which I put through a speaker as a musical note ("musical" is debatable). I can get lots of different notes by changing the resistance going through the 555.

I want to set up a circuit where I can cycle through 8 notes or so with just one button that you keep pressing. That is, I want the output of the 555 to be diverted through 8 different paths in turn when I press the same button. Each path has different resistor combinations so produces a different note.

I have done some research and a 4017 decade counter or a multiplexer seem like they could work, but I am really in the dark. In particular I don't want to distort the frequencies from my 555 since it will make the notes flat or sharp.

What are the common solutions for this situation?

  • 3
    \$\begingroup\$ This circuit is similar to what you are talking about - eleccircuit.com/… \$\endgroup\$ – HandyHowie Mar 13 '17 at 13:04
  • \$\begingroup\$ If you want to play the notes sequentially, the schem provided by HandyHowie is maybe what you are looking for. But if you want to play the notes like a piano, with one button is just impossible. \$\endgroup\$ – Tagadac Mar 13 '17 at 13:22
  • \$\begingroup\$ It's not clear if you want to steer the output of the 666 timer to different places, or want to change the frequency the timer is emitting. In any case, this kind of complexity is much easier to implement with a microcontroller. \$\endgroup\$ – Olin Lathrop Mar 13 '17 at 13:24
  • \$\begingroup\$ @HandyHowie - Yes I think this is what I want, like those old toys that played a different sound effect each time (machine gun, bomb, etc.). \$\endgroup\$ – thatsagoal Mar 14 '17 at 0:42
  • \$\begingroup\$ @OlinLathrop - Sorry I didn't have it quite clear in my head. I want to change the frequency the timer is emitting. \$\endgroup\$ – thatsagoal Mar 14 '17 at 0:42

Hopefully I am not breaking any rules here, but unfortunately, I do not have the rep to just add a comment above, so this answer basically just adds to HandyHowie's suggestion (and also saves me the time of drawing out the entire schematic).

That is exactly what I would have done, except: Using the circuit he supplied, remove the 555 timer connected to pin 14 of the Decade Counter and replace it with this circuit:

Tactile Clock Pulse

Pressing the momentary switch will advance the counter, rather than the timer.

EDIT: For what it's worth, here is a schematic of what I think you are looking for. I just used a block to represent your existing astable circuit. This will give you 8 steps sequentially activated with a button press. If you want to utilize all 10 available steps, just add the Resistor/Diode series to Pins 9 & 11, and ground Pin 15. Of course you can also add versatility with potentiometers in each R/D series to be able to adjust the tone of each step, too.

Sequential Tone Generator

| improve this answer | |
  • \$\begingroup\$ I've tried this out and it basically works. Thanks! However, you also need diodes from each resistor set to the 555. I'm not quite sure why, but I suspect it could be the 555 sending current the wrong way. \$\endgroup\$ – thatsagoal Mar 14 '17 at 14:19

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