Reverse amperage caculations

[MrDEB]

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.

 

[Reloadron]

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

 

[MrDEB]

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.