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Car Timer with Atmel atTiny45

Idea: I all too often forget to turn off amateur radio equip in my car, resulting in low car battery charge !
and the risk to damage the battery permanently or having trouple starting, or wasting fuel on charging.
I need the posibility to listen and talk in radio when the car engine and ignition is off,
so I invented this automatic timer.
Will sense engine on on the voltage, engine on = radio on,
engine off = radio still on while time out is under 20mins.
This whole project was made in 2 hr in total, so forgive me for lame qual schematic :-)

The schematic is quite simple, I just used what I had avail in drawers.
The linear regulator I used is a normal LM7805 type, but this one only draw 2mA
The AVR uses MUCH less than this, since it is in sleep most of the time.

A little component sample box was used, right size and for free.

The power N-Mosfets I got had too hi on-resistance, so I just used 4 in parallel, they was also for free.
I need 10-20Amp load with no wasted heat, and no relays that will give me trouple some day.

Good contact and cooling to make it run safe for many years

First I took a piece of vero-board in wrong size, for the box later found.
A better way to do this, is to find the box first, then make the board fit, then add components..

Mounted in my car.. it works great for stupid people like me, that often forget to turn off stuff.
This construction can be used for many other things in cars and camping like, TV, Game, Heaters, Coolers, GPS, PC systems.

Download the HEX file for free ?? car-timer.hex if you like it and use it, please transfer a small fee to my paypall:

my first name at webx dot dk, thanks and good luck.

Made Aug 2006 Thomas Scherrer OZ2CPU