Reverse amperage caculations

Have a working project but at present for testing on the bench am using a 9vdc wal wart 200ma
End use the project will be connected to an automobile which has a voltage supply of 12-14v dc.
testing using the wal wart I show 80ma at 9v
reverse calculations I show draw 1.2 amps in the car if I figured correctly?
still need to insert a fuse so at 1.2 amps thinking maybe a 2 amp fuse?
pictured is a combo unit which I had planned but going to build two seperate units. at present, regarding reverse calculations, the PIR, photo transistor and associated components are not included (I thought I had a png file with just the unit under test)
are my calculations correct and fuse size?
Audioguru contributed the mosfet H bridge design, thanks it works on the bench now to test in an automobile.

Before anything else if your PIR is one of those Parallex units you have it on the 12 volt side of your regulator... bad thing. Next, your PIR drives a transistor with a 12 to 13 volt collector using a 22 K resistor. When the transistor is off won't that place 12 volts + on your PIC input?

Ron

The PIR is one of 5 I purchased from SURE electronics last year. On the garden unit which does not use the H bridge, the unit is battery powered. Found I can eliminate the transistor and connect directly to PIC but it dosn't seem to work as good. As pictured it works fine except I found I needed the photo transistor (going with Cds) so unit will turn off during the day (infrared does not function correctly during daylight as daylight IS IR)
Using the Cds as a resistor ladder (Pic is set up with ADC. The resistor connected to the Cds is a pot. so adjustments can be made as all Cds cells are not alike.
The newer PIR units from Sure have a Cds and 3v or 12-24v Vdd. I need to recheck Vdd but I recall 3.3V
The H bridge is whats drawing all the current.