Currently I am looking for a (preferably rather compact circuit) that will test whether a certain signal has been on for X amount of seconds.

Just get a Pulse Length Detector, you might say. Only there's a problem with that. When the input signal gets turned off and then back on, the old 'test' will still be successful and a signal will be emitted.

Is it possible to somehow make a 'perfect' test for an uninterrupted redstone signal of X seconds that does not get confused by several shorter pulses?

  • Are you allowing command blocks in the solution? It's still possible without them, just a lot harder.
    – MBraedley
    Mar 8, 2015 at 17:10
  • No, is meant for vanilla survival. Sorry for not being clear in that regard.
    – Stigma
    Mar 9, 2015 at 10:08

1 Answer 1


Use a long clock of the length of time you need, that is disabled when it has no input signal and starts when it gets signal.

To make the clock only tick once: latch its output, invert it, AND it with the target signal, and feed that into the clock's enable line instead of the raw target signal. Finally, attach the inverse of the target signal to the reset line of the latch, else it will be a one-time-only circuit.

Take the output either before or after the latch, depending on whether your desired output is a pulse or a constant signal.

  • I think I get the general gist of the logic; I dare say I almost got that far in my head but the details are a problem. What exactly is a 'long clock'? What sort of latch? Is there any chance you could whip up a quick screenshot? The saying regarding images and a thousand words comes to mind. :)
    – Stigma
    Mar 9, 2015 at 10:11

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