filter out noise by time
I was wondering is there an easier/cheaper way into creating this, so
  that no micro is needed? with some passive components?


Micros cost very little and no, you can't reliable achieve this with only passive components but you could use an RC low pass filter and a comparator with hysteresis. This will give you something like what you want but there may be caviats. For instance, with an RC low pass filter, your input may be 12 volts for 14 seconds then fall back to 0 volts (the other state) for a couple of seconds. Then it goes back to 12 volts for 3 seconds and it triggers. So do you want this functionality?

If you are unsure what you really want then stick with the micro because it's dead easy to re-engneer different functionality.