I have to make a circuit in which i have to produce three outputs(on speaker buzzer sounds)

  1. First is for 20 seconds on 5 sec off 10 sec on 5 sec off 5 sec on and 5 off( this alarm sequence for 3 minutes)

  2. Second one is 5 second on 5 second off (this alarm for two minutes)

  3. Third is 10 seconds on 5 sec off, 5 seconds on 5 seconds off (this alarm for 3 minutes)

I have to use 3 push buttons/switched for this.can anyone guide me how to use 555 ic for this.. I have resistor and capacitor values for times but i am not sure about circuit.

  • 4
    \$\begingroup\$ Forget using a 555 and think about using a microcontroller instead e.g. ATTiny or arduino \$\endgroup\$ Commented Dec 16, 2016 at 19:20
  • \$\begingroup\$ #1 adds up to 30 seconds, not 20. If I'm reading it correctly. \$\endgroup\$
    – jonk
    Commented Dec 16, 2016 at 23:00

1 Answer 1


The complexity of the sequence and the relatively long times makes a 555 timer completely unsuitable for this task. Actually, you'd need quite a few of them for timing the various parts of these signals, and then some logic to gate and sequence things. That would turn into quite a ratsnest of stuff.

Use a microcontroller. What you ask is relatively simple to do in even a modest micro. All you need from one is 3 inputs and 3 outputs, which just about every micro with 8 or more pins can do.

In the firmware, divide the clock down to get 1 second events. Then write code that waits for N one second events between doing things. I'd set up a 1 ms periodic interrupt to debounce the input buttons, and use that to also count to 1000 to create the 1 second events.

This is really a rather simple task for a microcontroller.

  • 1
    \$\begingroup\$ plus every microcontroller can toggle a pin - no matter whether you buy an arduino board for multiple \$10^1\text{ USD}\$, a sub-1 USD AtTiny, a 32bit ARM Cortex-M0 of the same price class, invest several dollars for an ARM that has several MFlops in math power, a or spend literal cents on any 8051 clone. Just use what seems most usable to you. Also notice that you can synthesize the sound for your speaker on anything but the weakest microcontroller yourself – no need to buy a buzzer that buzzes on itself, just switch a PWM unit on and off. \$\endgroup\$ Commented Dec 16, 2016 at 22:56
  • \$\begingroup\$ @Olin Lathrop. You only need 3 input pins and one output pin (the speaker buzz) for this application. \$\endgroup\$ Commented Dec 16, 2016 at 23:32
  • \$\begingroup\$ Thanks..actually i have not worked on micro controller much.can anyone guide which micro to use? Plus can i use labtool 48, inelligent universal programmer by advantech to program it? \$\endgroup\$ Commented Dec 17, 2016 at 4:02
  • \$\begingroup\$ Can any one refer me to a relevant code on microcontroller? \$\endgroup\$ Commented Dec 17, 2016 at 6:17

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