I've been asked by our gardener to monitor the behaviour of our irrigation timer which he suspected of being faulty. So i came up with this simple event logger (i could have used a microcontroller...).This circuit relies on an ne555 and cd4017. It simulates some button presses on a printing calculator so that, when a trigger signal is present, the unit records date and time onto the paper roll via its own printer.

            See the video below.