I'm building a box to collect solar heat. It will have two small fans 12vdc using 1.25w each. Each will be powered by a 1.5w 12vdc solar panel. So I will build two identical circuits to run independently. I want to delay the start up of the fan, but I will have to be able to calculate what values to change based on my delay needed. Maybe 5min, may 10 min. Not sure. Also, I will need a filter for the current because it may have some pulses in it as the solar panel is a battery tender type. I can use capacitor for filter, can I also use one for a delay? How do I calculate the values for filter and delay? Or should I use a different way for the delay?