Car Gps unit power up on ignition on

Discussion in 'The Projects Forum' started by tonyjms2005, Jul 23, 2014.

  1. tonyjms2005

    Thread Starter New Member

    Jul 23, 2014
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    0
    Hello

    I have a windows CE 6.0 gps unit that I am try to setup so that when it gets power from the battery, the unit automatically powers up.

    At the moment I have switch the unit on via the momentary push button power switch once power has been applied.

    Is it possible to use a circuit or a capacitor on the switch contacts to simulate a push button event when the unit gets power?

    Thanks in advance

    Antony
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,150
    3,058
    I don't see how you could do that without getting inside the GPS. Are you comfortable opening it up?
     
  3. tonyjms2005

    Thread Starter New Member

    Jul 23, 2014
    21
    0
    Hi
    Thanks for the reply.
    Yes I have already opened it up as my car already has sat nav but its useless, so I am upgrading to a touchscreen one.

    I have considered either using a 555 monostable swtich or perhaps a capacitor across the power switch terminals?

    Thanks

    Antony
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,150
    3,058
    The switch probably provides a touch to either ground or to V+, to trigger start-up. It would be nice to know which it is. So can you measure the voltage, versus battery V-, on the two switch terminals? Measure again against battery V+. Finally, measure ∆V across the switch terminals.

    It's possible that touching your voltmeter leads across the terminals of the switch might be enough to look like a switch closing to the electronics. It may turn it on.
     
  5. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,394
    1,606
    Many many manufacturers make "system supervisor" chips, most are 3 terminal devices that sit across the power supply lines and fire the third terminal at power on.

    Options include valid power range, active high or low output, open collector or push pull, delay time between valid power and output, and also output pulse width. One option you may not find is a leaded package: all the ones I have used were SMD only, SOT-23 package.

    In essence, they could make the momentary push for you once they sense the power is on.

    And yeah, you can probably arrange a '555 to do the same thing, just more parts.
     
  6. tonyjms2005

    Thread Starter New Member

    Jul 23, 2014
    21
    0
    Hello
    Thank you for your replies, with regards to the circuit options you have described can you expand on possibly the most suitable? The power supply will be five volts from an existing circuit from the old gps system from the car.

    You will have to excuse my lack of knowledge of advanced circuits.

    Kind regards

    Antony
     
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