"Infotainment" (fancy radio) accessary current?

Discussion in 'Automotive Electronics' started by ErnieM, Oct 27, 2015.

  1. ErnieM

    Thread Starter AAC Fanatic!

    Apr 24, 2011
    7,388
    1,605
    I'm in the middle of installing an AM/FM/XM/BT/DVD/GPS radio into my 2001 Ford POS.

    I was thinking of tricking out the accessory (or ignition) power input to turn on with the key then delay the turn off when the key is off until a door opens. The logic of that is simple though I do question how much current I need supply.

    Is the accessory input a simple signal or is there some current drawn here? The unit specs are mute, and I've already spliced the cable preventing a direct measurement.

    (Seriously though, I do love my truck.)
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,126
    3,048
    My 2002 Chrysler minivan does exactly what you describe. The radio will keep going for a minute after the key is removed, unless the door is opened during that minute, in which case it goes off immediately when the door is opened.

    I'm not sure I understand your question. What do you mean by accessory input?
     
  3. ErnieM

    Thread Starter AAC Fanatic!

    Apr 24, 2011
    7,388
    1,605
    There are two "power" inputs to the unit. One is the constant 12 V battery power, the other the accessory power that is switched on and off with the key. I would believe the former suplies the main current to run the thing, while the latter is mostly a switching signal with a low current draw.

    I am asking to size that "delayed off" switch as I would have to make one. Is it switching milliamperes or amps? I assume it's is low current but I don't built circuits on a bedrock of assumptions.
     
  4. #12

    Expert

    Nov 30, 2010
    16,298
    6,809
    I can see it both ways, and nobody can guess from here, so measure it. Which line jumps into power mode when the switch is in "accessory" position?
     
  5. wayneh

    Expert

    Sep 9, 2010
    12,126
    3,048
    I also admit ignorance but my guess is that it's the other way, that the "smart" power supply is controlled by the vehicle and full power is delivered to the radio. I can't explain why you'd need to run two power wires to the radio.
     
  6. ErnieM

    Thread Starter AAC Fanatic!

    Apr 24, 2011
    7,388
    1,605
    One wire is definitely the main source of power. It is back stopped with a local (on radio) 15 amp fuse.

    The accessory input is switched power that acts as an enable line. A radio needs both if it has features like a clock that needs constant power to keep on keeping on.

    Not that I have done many car radio installs but I have never seen them run off just one power wire, excepting the times I wired them just that way so it would keep playing until I turned it off with the knobs.

    I just want to do it the modern fancy way now that I have a modern fancy radio.

    I put some 12v relays on order, that should be a safe and sure way to control the aux power in.
     
Loading...