Circuit Requirements for a 30 min continuous on off cycle
30 minutes is a long time for analog electronics to time.  This would be done by a small current on a capacitor eventually changing its voltage past a threshold.  Unfortunately, for such a long time the current to charge and discharge the capacitor will be too large relative to the leakage current of the capacitor and surrounding circuitry.

A simple way to do this is to use a microcontroller.  Even the cheap and tiny PIC 10F200 can do this easily.  The internal oscillator of the micro is good to a few percent.  It runs at 1 MHz instruction rate, which you can easily divide down by whatever number you want to get arbitrarily large time delays, all at the same accuracy as the main clock.

Other options are to count power line cycles (since that is often a handy existing signal with well known frequency).  However, all these schemes will take more hardware than a PIC 10F200, which only needs power, ground, and a bypass cap to change the state of a pin every 30 minutes.  Of course that can also be easily modified for different delays or patterns.