Hello,
I am working on a larger project, but one of the many small tasks is we need a decent way to spit out an input to a microcontroller when we see a vehicle's ignition has been turned on or off.
We have a potential solution. Simply tap into the fuse box onto one of the various ACC fuses that only turn on when the ignition is on. That is all fine and dandy except A: Its a bit invasive. B: It changes based on the vehicle. I would like a solution that is more cross-platform and easier for a user to install. I am limited in what I can say about the rest of the project, but all I really need is some sort of "tell" that I can either directly or step down the voltage (know how to do that already no problem there) so that I can feed a GPIO pin of a microcontroller elsewhere in the system.
I would like to come off a usb or cigarette lighter. On some cars, this would work great. Some cars have ports that only turn on when the ignition is on.
However, on some cars they are on all the time. Also, on some cars you have a few on all the time and a few on some of the time.
I want to design a circuit that can be used on either variant, either on all the time or on only when the ignition is on. I think I have an idea but not sure if this is correct.
I know when you crank the ignition the voltage dips for a short period of time. Does this dip always pass onto the rest of the ports like the cig lighter and usb? If so I believe I could design a circuit that sits there expecting to see either 0v or 12v, but if it ever sees a range of say, 6-10v, it lets me know. The big question is whether or not my assumption is correct that the cig lighter/usb do in fact dip during crank?
Any thoughts? I plan to go do some testing today but just wanted to put some feelers out as well.
I am working on a larger project, but one of the many small tasks is we need a decent way to spit out an input to a microcontroller when we see a vehicle's ignition has been turned on or off.
We have a potential solution. Simply tap into the fuse box onto one of the various ACC fuses that only turn on when the ignition is on. That is all fine and dandy except A: Its a bit invasive. B: It changes based on the vehicle. I would like a solution that is more cross-platform and easier for a user to install. I am limited in what I can say about the rest of the project, but all I really need is some sort of "tell" that I can either directly or step down the voltage (know how to do that already no problem there) so that I can feed a GPIO pin of a microcontroller elsewhere in the system.
I would like to come off a usb or cigarette lighter. On some cars, this would work great. Some cars have ports that only turn on when the ignition is on.
However, on some cars they are on all the time. Also, on some cars you have a few on all the time and a few on some of the time.
I want to design a circuit that can be used on either variant, either on all the time or on only when the ignition is on. I think I have an idea but not sure if this is correct.
I know when you crank the ignition the voltage dips for a short period of time. Does this dip always pass onto the rest of the ports like the cig lighter and usb? If so I believe I could design a circuit that sits there expecting to see either 0v or 12v, but if it ever sees a range of say, 6-10v, it lets me know. The big question is whether or not my assumption is correct that the cig lighter/usb do in fact dip during crank?
Any thoughts? I plan to go do some testing today but just wanted to put some feelers out as well.