Power up device for 4 seconds!

Discussion in 'General Electronics Chat' started by TheDag, Feb 8, 2012.

  1. TheDag

    Thread Starter Member

    Jan 1, 2010
    94
    1
    Hi,
    I Have Bluetooth device that I should click on the switch for 4 seconds for the device power up.
    the switch is 2 pads in the PCB, 1 of them connected to the battery+ of the device.
    Now, is this schematic will work as "automatic clicker" ?
    [​IMG]

    Thanks to "kubeek" from the forum that built that schematic !!

    Thanks in advance...
     
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    What's an automatic clicker?

    Can you post a link to the other thread where Kubeek posted his schematic?
     
  3. PaulEE

    Member

    Dec 23, 2011
    423
    32
    Why did you repost this thread???

    The "automatic clicker" (to praondevou) was a 555 triggered electronic switch that was supposed to toggle on/off a bluetooth module.

    Despite our best efforts in the previous thread, a '4066 wasn't good enough.

    After successfully convincing the OP that "zero ohms" was impossible, OP settled for a few.

    kubeek suggested the dual transistor switch you see in the original post (and the top of this one), and now the OP wants to know if it'll actually work.

    I think the OP should BUILD IT, personally.

    When asked what this switch was interfacing with, he either ignored the question or does not know. In either case, I tried to explain that if he was switching a logic signal into a microcontroller, nearly any electronic switch could work, since there won't be high currents running through it (and, hence, the "on" resistance isn't as important). Couldn't get through to OP, though.

    So, here we are :)

    The original:
    http://forum.allaboutcircuits.com/showthread.php?t=65539

    The ORIGINAL circuit:

    [​IMG]
     
    Last edited: Feb 9, 2012
  4. Wendy

    Moderator

    Mar 24, 2008
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    As drawn, that schematic will not work. There are no power connections to Q2, so there is no way for current to flow across the BE junction. No Q2 BE current, no Q2 switch, it is not complex.

    Q1 BE can have current, but Q1 collector is a dead end. It goes to no power. Again, this will not fly.
     
  5. PaulEE

    Member

    Dec 23, 2011
    423
    32
    TheDag,

    Once again...I ask:

    Is the switch on your circuit board switching a logic signal or battery current?
     
  6. TheDag

    Thread Starter Member

    Jan 1, 2010
    94
    1
    I really dont know, all i know is one pad is connect to the battery+ of the device...
     
  7. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    Ok, I saw it. It's one of "those" threads... :-/

    The button is apparently waking up a uC or something so there isn't really current needed. But with the information provided it's almost impossible to really help.
     
  8. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Let me explain guys, TheDag has a bluetooth module that is activated by a 4sec button push. The button is wired so that it pulls the junction of switch1-r1 high, and he wants it activated from a 555 running on 12V. He had some problems with the 4066 conducting all the time (it was probably shot), so i suggested this circuit which should work allways.

    We discussed this in icq, so most of the information is missing in that thread.
    The first picture is supposed to show the connection between the 555 and the blutooth.
     
  9. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Why not use an "OR" gate with one of the inputs to ground and the other from the 555 monostable? when the 555 timed out the "OR" would then be off and no 'ohms' :) would be used.

    It could be done with a diode from the 555 too.
     
  10. Wendy

    Moderator

    Mar 24, 2008
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    I have done something similar with RC toys, interfacing a C64 to its joystick. R1 can be eliminated (may have to be as a matter of fact). As long as the current is flowing the correct direction between the CE of Q2 it will still act like a switch.
     
  11. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    R1 was the pulldown resistor inside the bluetooth.
     
  12. PaulEE

    Member

    Dec 23, 2011
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    thank you.

    Perhaps TheDag could measure current through the switch with a meter to determine if current is actually drawn or if it minimal. Then, we can set off inspecting what signal actually needs toggled and how.
     
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