528t to switch 2 power source for car lcd

I've just installed my car LCD/DVD players on RAP 12V circuit. Problem is the DVD unit does NOT have last-position memory. So at every gas/potty break on long drives, my kids would need to re-start the movie or go to 'select scene' etc. I am hesitant to power the system to constant 12V circuit, as kids might leave them on overnight & drain car battery. My idea is to provide a switched 12V constant that I can use ONLY when stopping for a few minutes. So, normal operation remains on RAP circuit, and when stopping for gas, I want to flip a switch so DVD remains on when engine is off. Once we get going, I want to turn the switch off, and DVD go back to normal operation. Can I use a DEI 528T to do this? The timer function would momentarily "bridge" between the power supplies (RAP & Constant) so there is no interruption to the DVD unit. I am also concerned abt 12V constant going back to RAP circuit in car fuse block (& messing other electronics). Of course the above is hoping that during cold start cranking, the constant on do not die. Help appreciated!

20 Minutes with a Directed tech support, and I'm more confused then ever. He said the 528T canNOT be triggered by a 12V +ve signal from a switch. Only be a negative signal, or upon REMOVAL of a +ve signal that is first introduced into the trigger wire. His recommendation is to wire the switch to be always on, and turn it off to trigger the 528T. This is NOT ideal, as my switch has LED indicators, and I don't like the idea of having 1 switch with the LED ALWAYS ON as "normal" operation. Again, my original idea is to connect ORANGE 87A (N/C) to 12V RAP, BROWN 87 (N/O) to 12V Constant, and use the timer function to bridge the switching to prevent power flicker going to YELLOW 30 to LCD/DVD units when the 528T is triggered with 12V+ve from a switch. Could someone who has worked with a 528T help? PLEASE?

Don't know if it's necessary to try to figure out a way to use the 528T for your application; if it doesn't do what you want. You could add a relay driver circuit that can give you a delayed turn off when the RAP shuts off; just pick a resistor/capacitor combination to set the delay time to as long as you need. The relay driver would control a relay that supplies power to your DVD. When the RAP goes off, the relay would remain on for a period of time of your choosing, like 5 minutes, before shutting off. If you return and switch the car back on within that time, the power to your DVD would remain uninterrupted. Wouldn't take much to put together, just a MOSFET, resistor, capacitor, and a couple diodes. Depends whether you want to deal with electronic bits or get something already made.

dualsport wrote: Don't know if it's necessary to try to figure out a way to use the 528T for your application; if it doesn't do what you want.

Thanks for your answer. Came to the same conclusion, especially when I remembered that my switches themselves are powered by RAP. Engine off = switches off. Going to use an ELK-960 Delay Timer and a constant source. I won't be able to control the on-off duration as I can with a switch, but on the other hand, I won't be the one forgetting to turn it off and get a dead car. Thanks again!