I would like to be able to use an Arduino as a timer control to switch on/off a 120VAC load. I think I can do that with the Arduino triggering a small relay controlling the 120V contacts. But I need a display to show the timer duration value and a potentiometer or encoder (knob) to control the duration. Time values will be short, .1 second to 20 seconds, but will need to be easily changed with the pot or encoder and shown on the display. Ideally, the display would show the duration and count down to zero when triggered by a separate electrically dry contact closing. A few LEDs to show power on, relay energized, and one to signify the duration is able to be changed with the knob (a "set mode" indicator).
I can see how to set a timer duration in the code, but I need to be able to press a button or something and manually turn a knob to set a different duration for the timer without having to write/change the code every time I want to change the duration.
Any help pointing a newbie in the right direction where to look?