My project is...I would have a circuit which will be power by 12 v DC only when car engine is running. Then, in time t =5 secs, the capacitor will fully be charged while engine still running or maybe still running for 5 or 6 hrs....still then capacitor is full. Now, the main point..as soon as engine is OFF, the capacitor will be discharged which will activate a relay to turn on the load bulb connected to this relay as long as the charged is in the capacitor. Could any kindly sketch a diagram of this project. Thanks.