Variable Duty Cycle DC Motor Timer

Can any one help with the design of a timer that would turn on a small DC motor for 1 minute, followed by a variable 20 - 40 minute rest period, to cycle continuously.
I am fully competent in building the building side, but the maths involved escapes me.


There are off the shelf units to do so if interested, digital time delay cycle timers that have programmable on/off times and number of cycles to execute with the option of repeat indefinitely.
Macromatic TR-63xxx or TR-65xxx repeat cycle timers, about $90 from Newark

Also came across an Amperite 12DF/FHDFA for about $55, also from Newark.

These may be overkill (handle up to 10A loads), just a suggestion if you need a minimum of hassle.

Above is a snippet.

I agree with D2Aman but also you state “by a variable rest period”.

What’s setting this variable rest period?