In Make: Electronics, on page 169 you are shown how to chain two 555 timers and use the first one to modulate the tone of the second one. I constructed this circuit on a breadboard and it worked good - a decent siren sound.
It also suggests several component value changes to modify the sound. My schematic shows the top half of this circuit only since my question pertains to the first 555 timer. One of the suggestions - to modify the sound of the first 555 timer - is puzzling me:
"Halve the value of R5 while doubling the value of C4, so that the cycle time of IC1 stays about the same, but the On time becomes significantly longer than the Off time."
But wouldn't this result in the charging time of C4 (the 'output-on' time) staying about the same, and also the discharging time (the 'output-off' time) staying about the same? (since the cap charges through both resistors, but discharges through only the bottom one). Thanks.
It also suggests several component value changes to modify the sound. My schematic shows the top half of this circuit only since my question pertains to the first 555 timer. One of the suggestions - to modify the sound of the first 555 timer - is puzzling me:
"Halve the value of R5 while doubling the value of C4, so that the cycle time of IC1 stays about the same, but the On time becomes significantly longer than the Off time."
But wouldn't this result in the charging time of C4 (the 'output-on' time) staying about the same, and also the discharging time (the 'output-off' time) staying about the same? (since the cap charges through both resistors, but discharges through only the bottom one). Thanks.
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