Hello, I am currently working on a project of installing a dashcam in my car. The biggest problem I have is that the dash cam drains battery power while the car is in the garage, which I want to avoid.
So I thought of installing a switch that cuts power to the camera while the car is in the garage. This switch would of course be installed in the car itself and the external sensor would be in the garage.
Reed switches would be ideal for this purpose, except they wouldn't work through the car ground and as far as I know they don't work at long distances (a few meters).
How is the dashcam powered now? Most cars have an accessory bus, which provides power only when the engine is running.
Commercial car detection systems use a buried wire loop, and sense the change in inductance resulting from the large iron mass of vehicle entering the loop's magnetic field.
The idea is that the dash cam is powered even after the car is turned off. This allows it to detect parking accidents. There are systems that prevent the battery from being discharged below 12V. But if I park the car in the garage, I don't need it.
When I get home and leave the car in the garage, the dashcam runs all night and drains the battery so there will be no juice left tomorrow when my car is in town where I need the dashcam.
I tried to find proximity sensors on google. The thing is that the switch needs to be installed inside the car and the external sensor outside. Know of a model that would do this?
Please understand that my response is not directed to you, but is in the context of general hobby programmers:
This is what happens when a project is constructed but not designed; that is, you have a working idea, but the idea does not meet your bigger goals. Thus, you are in scope-creep mode!
Essentially, you must create an add-on solution to something that could easily have been incorporated in phase-one. For the benefit of others who are considering putting Arduino projects into the real-world, one should take pen and paper (or Windows notepad) and work through a decision tree of nice-to-have, required, and "fluff."
For your specific issue:
small IR transmitter, small IR receiver placed so that when you park in the garage, the IR receiver can disable power to the monitor.
a Reed switch on front bumper, a magnet-filled tennis ball dangled by twine from ceiling, and position to meet the switch when car is "docked"
... and many more Rube Goldberg methodologies.
Point is, think through your need before building your final unit. Personally, I generally attempt to include add-ons during prototyping because at that point the code is 90% complete and adding the nicities is somewhat simple.
Another approach might be a timer that cuts power to the camera after some appropriate period.
The critical requirement is to not drain the battery and you'd want to avoid that situation regardless of whether the car is in the garage or in long-term parking somewhere else.
I would think that a dash cam would draw so little current that leaving it connected to the car battery over night would not significantly drain the car battery. How much current does the camera draw?
I think a better approach for a "who hit my bumper" security system would be a secondary rechargeable battery fed by the automobile "switched" aux power.
Idea one: Timer wouldn't solve it because it would work in the garage as well as outside. So if the camera turns off after 1 hour in the garage, it would also turn off after 1 hour when I'm outside where it has to run for 8-9 hours.
Question two: As I said before, it runs for 15-20 hours on a full battery, which is a lot. Imagine if you would record a video with your mobile phone for 20 hours! Most phones would die after couple of hours. You also have to think about the cycle. When I start driving to work, the battery only charges a little, runs for a few hours until it has 12V again and then charges up again so that it can be drained again overnight. So I'm always on the bare minimum because of this garage thing.
Regarding the last question: The dashcam turns itself off when the power is interrupted.
I really think there must be a switch that turns off when near some sort of sensor. I would be grateful if someone who knows the model could also post it here (not sure if this is allowed in the forum?).
I don't think the thing you want exists. If it does and someone posts a link to one then I too will learn something. A reed switch or a Hall effect switch will only operate within a few mm of a magnet. Anything longer range requires power, which kind of defeats the whole point of what you are doing.
Does the dash cam really have a 12V battery? No battery chemistry actually gives 12V exactly, so what is it really? And how do you know?
Read my posts again: Dashcam uses car battery and Power Magic Pro stops it from using it after it drains it to 12V (actually 12.4V but that does not matter here)
Okay, let me summarize your request then. You would like advice on what kind of switch you could use that senses the proximity of your car in the garage and turns off the dash cam but you refuse to tell us how that switch would be connected to the dash cam. Is that about right?
No I just fail to understand your question. Switch will interrupt the power to the cam once it detects a presence of the nearby sensor just as reed switch interrupts power in the proximity of a magnet.