help with timed relay circuit

Discussion in 'The Projects Forum' started by skinner927, Jan 23, 2008.

  1. skinner927

    Thread Starter Active Member

    Dec 31, 2007
    36
    0
    ok, It's more than help. I don't know any way to go about doing this.

    I'm using it for a car radio, The radio doesn't turn off when the car turns off. It's not a problem with the radio, it's the car model years that vary, dont worry about it.

    Is it possible to make a circuit that will open a relay for one second when given power, and then open that relay again for one second when power is lost?

    So, when the car turns on, the radio would turn on, and same with off.

    I can wire up to the actual switch in the radio. When I say relay, I say relay because I've only used relays before. I guess I could use a transistor but I don't know what the voltage is on the switch, so I don't want to use a transistor so it doesn't burn it out. Again, i've never used a transistor before so I don't even know what their maximum voltage ratings are. It wouldn't be more than 12 volts, its probably lower than that though too.

    Thanks for any help or insight anyone can give me on this.

    Thanks :)
     
  2. gee_emm

    Active Member

    Jan 16, 2008
    34
    0
    Not to sound like a smart a_s,...but wouldnt it be easier to install a toggle switch to the radios power? maybe mounted near the ignition or something? ,... just a thought.
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Do you have access to the point where the radio gets power? Can you move the power take off to a part of the electrical system that turns on and off with the ignition switch?
     
  4. skinner927

    Thread Starter Active Member

    Dec 31, 2007
    36
    0
    ok, here's a better description.

    The radio comes from a 2003 Jetta, I have a 2001. In 2003 they added a different/better/bigger radio. The problem with this, is that in 2003 they also made the radio able to talk to the ECU (Engine Control Unit/cars computer). The ECU tell the radio when to turn on and off. So if you put this new radio in an older car (after you spend more than this radio costs in wire adapters :mad: ) it can only be turned on and off via the power button on the front. (Luckily Volkswagen designed these radios to be turned on manually even if the car is off, this is why this works.)

    I would simply wire up a relay to the ignition wire and then to the switch, but this would only turn the radio on, I'd still have to turn it off.

    Also, I can't just pull the power from the radio because then I'd loose all my radio settings and I'd need to enter an anti-theft code every time it would turn back on.

    Thanks for the responses :D I hope someone can help me out :D
     
  5. gee_emm

    Active Member

    Jan 16, 2008
    34
    0
    The way Im reading this is,... either way, you'll have to manually turn the radio on and off, even if there is a relay to the power. Or at least on, when power first gets there (unless it automatically turns on with power?) It shouldnt lose memory though. Theres the power, grnd, and memory which is a lower voltage, so even breaking the circuit, it should retain. Going through the ignition, Id think you might get alot of noise, and hear the engine revs over the speaker.
     
  6. skinner927

    Thread Starter Active Member

    Dec 31, 2007
    36
    0
    I'm trying to make a circuit that will basically press the button for me. This radio does not have the traditional ignition line as after market radios do.

    I'm not modifying any of the connections that the radio usually uses. I'm just added this circuit so I don't have to turn the radio on and off manually.

    I'm wiring directly up to the switch on the front of the radio
     
  7. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Mayhap some revision of the following will work...
    radiothing.jpg
     
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