We had a special request for a modified version of our REUK Super Timer 2 for use setting dosing levels during plant development.

Our super timer can be programmed to close a relay for an interval from 1 second to 99 hours, and then open that relay for from 1 second to 99 hours repeating. It is a very useful and popular product, but in this particular application it was necessary to make the programming of the ON and OFF durations as simple as possible and to also display the current settings so that it was immediately obvious to anyone looking at it what those settings were.

Pictured above is our solution to this problem. The possible ON durations required were 1,2,3,4 or 5 seconds, and the OFF durations 1,2,3,4 or 5 minutes. Therefore there are two buttons – one to move through the ON options 1 to 2 to 3…etc seconds, and another button to move through the OFF options 1 to 2 to 3… etc minutes. The green LEDs show which ON option has been chosen, and the red LEDs show which OFF option has been chosen.

Because of the large number of inputs and outputs, 10 LEDs, two buttons, and a relay, we chose to use Arduino for this project, but as a standalone microcontroller as explained here: Standalone Arduino on a Breadboard so that everything could be put tidily on the one circuit board.