Recently, on a business trip, I had a rental car. Now, in my car, all of my 12V power outlets are always on. On the rental car, some of them were always on, some of them were only on when the car was on. Is there a way that I could hack my existing 12V outlets to either have some of them only be active when the car is on, or better, add a simple toggle switch that will toggle them between running always or only when the car is on?
Electronic – Modifying an automotive 12V power outlet to disable power when car is off
automotivepower
Related Solutions
First, a note - there is already a negative in the cigarette lighter, no need to run a wire to chassis.
For your skill level, what you are proposing is quite complex. Instead I suggest the following setup:
Purchase a Seeeduino Stalker Waterproof Solar Kit. This kit is great. It comes with an Arduino with clock, SD card and XBee interface. It also comes with a solar panel, lithium battery and the charging circuitry on board. It can charge via the USB port or the solar panel. For the GPS, you may also want to look at their GPSBee which can slot into the board.
Purchase a cigarette lighter to USB charger. This will convert the car 12V to USB 5V which can power the battery.
In the car, connect the Stalker to the USB charger, and locate the stalker somewhere on the dash or parcel tray where it can also charge from the solar panel when the car is off.
Now you just have to spend hundreds of hours writing the code and debugging. Good luck!
The circuit cannot work-220K is too high for that transistor due to internal resistors. D2,3 do no good- they should be across coils of K3,5 (reverse biased, or you'll fry the transistors).
You could try replacing the transistors with power n-channel MOSFETs or greatly reduce the resistors and increase the capacitors proportionally to compensate. Something more like 47K and 470uF, 10V rating is okay for the caps but get 105C types. (Note: This was assuming the original circuit was calculated correctly, but I don't think so).
Edit: See below circuit. R2 represents the relay coil (80\$\Omega\$ at 25°C), this will give roughly a 1.7 second delay with 47K and 100uF. Change R1 if you want more or less time. I have used an IRFZ44 MOSFET in place of the Darlington.
simulate this circuit – Schematic created using CircuitLab
Best Answer
The solution ends up being very, very dependent on the exact model of your car and the physical distribution of the outlets within the vehicle.
You'll need a service manual for your car that has a complete wiring diagram. Check first before you buy one, as many only have block diagrams or step-by-step electrical tests instead of full wiring diagram.
Next, identify the 12V outlets on the wiring diagram. Outlets that are on all the time are likely connected to B+ (straight to the battery) via a 15A fuse. Outlets that are on only with the key will be connected to a relay that will be on with the run/ignition (IGN) or accessory (ACC) key positions. It, too, will have a 15A fuse upstream from the outlets.
EDIT: Even if your car doesn't have switched outlets, chances are that it has something that is switched on only with the key is in Accessory or Run positions. This is where things become very model-specific. If this is a classic car where the key switch directly controls power to the + side of the ignition coil, connect your new relay coil to that terminal. If it's a newer car, look first for an IGN or ACC relay. In the unlikely event you can't find one, find something that is switched on and off with the key, and tap the power to that device to operate your relay. Be sure to have transient protection (flyback diode or snubber) on your relay coil if you do this.
I'd recommend adding a separate relay and fuse in parallel with your existing IGN/ACC relay, then running dedicated 14-12AWG wire to each DC outlet. You can then install an SPDT toggle to switch between the existing (always on) and new (on with key) 12V supplies, with the center switch terminal connected to the DC outlet. Make sure that you use a switch that is rated for 15ADC or better.