I looked at the answer to "How to turn a 555 in astable mode into a decaying square wave" but this is really for an input to a speaker. I want the input to go into a counter to count the number of square wave pulses. I thought of using 2 555s the first one generates a square wave the second in monostable mode generates a square wave of some length ( acting as a modulator envelope). Then combining them with an AND operator. What do you think of this idea or is there a simpler way? I should explain in more detail what I am trying to do. I have a 4 digit Digital Counter panel meter. enter image description here There are 2 input leads when the input is high the counter increases by 1 . It also can increase by1 if I connect the input to a switch. When the switch is closed the counter also increases by 1. What I want to do is have the counter increase by fixed number. So say the switch is closed and I want the counter to go up by 5 or see set number.

  • \$\begingroup\$ This is a rather "foreign" question. A counter can easily count and stop. "iOS" is an Apple operating system. Define all inputs and outputs in your question. f, counts, driver V,I \$\endgroup\$ Commented Jan 15, 2019 at 1:26
  • \$\begingroup\$ If you are going to add a counter you might as well program a microcontroller. Do it all with one device and have complete flexibility. \$\endgroup\$ Commented Jan 15, 2019 at 2:09
  • \$\begingroup\$ For numbers less than 10 you could use a 74HC4017 to inhibit the 555, but using a micro makes a lot more sense. \$\endgroup\$ Commented Jan 15, 2019 at 16:18

1 Answer 1


You can do this with a pair of 555s, or a 556 (just two 555s in a single package), by using one as a monostable to enable the other, acting as an astable, for a period that generates the number of pulses. enter image description here If I were doing it, it's probably cheaper and simpler to program a PIC or similar to do this, there are plenty of 50 cent microcontrollers that will do this - plus you could use another pin or two for up-down adjustment of the pulse number.

  • \$\begingroup\$ Appreciate the suggestion to a pair of 555s. I will try it and after I get it to work and ask again how to use another pin or two for up-down adjustment of the pulse number. \$\endgroup\$
    – helman
    Commented Jan 21, 2019 at 8:28

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