On Thu, 29 Aug 2013 18:02:56 GMT, Jan Panteltje
wrote:

On a sunny day (Thu, 29 Aug 2013 10:18:17 -0700) it happened "Guv Bob"
wrote in
:

When 12VDC is applied to the input, I need a 12VDC output for 5 =
seconds.
+12
|
-----------------------------------------------------|
| | | |
| --- | ===
| / \ 1N4001 Load --- 1000uF / 16V
| 1u poly --- D2 | | C2
=== C1 |-------------- ///
| |--- d
-------------| | IRLZ34
| 4M7 | |--- s T1
[ ] R --- |
| / \ D1 ///
/// ---
| 1N4148
///


What discharges that 1000uF (and the 1uF) when the transistor isn't
turned on? Or are you assuming push-pull drive on the 12V?

When power is off C1 is discharged.
When power comes on the gate of MOSFET T1 is posive via C1,
and C1 slowly charges via R1,
R.C time, select a suitable capacitor and resistor.
The gate voltage slowly drops, and then T1 stops conducting.
When power goes off, then C1 is discharged again via D1.

D2 and C2 are needed to prevent transients on the drain (load line) of T1 piercing the gate electrode isolation layer.

Maybe replace C2 with a resistor and put 1K/12V zener before the cap.

IRLZ34 is a logic level (2 to 3 V gate on IIRC) MOSFET.

Alternative solution:
12 V light bulb - wakes up cat - cat drinks from cup - cup get lighter - balance turns - ball rolls, hits bell - you wake up, and swtich of the power.

12v heater boils off water so weight on microswitch is reduced. When
power is removed relay N.C. contact allows solenoid valve/flow switch
to refill water container. Oh, and wire in a beeper to bother the cat.