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amateur question about circuits — Parallax Forums

amateur question about circuits

ArchiverArchiver Posts: 46,084
edited 2004-02-16 19:52 in General Discussion
Hello,

I'm working circuit on circuit that works only when I have the logic
probe connected to my supply voltage and ground. I'm guessing this is
an obvious issue to someone with more experience then me.

If someone could point me in the right direction I would be most
appreciative.

If more info is needed I can provide it.

Thanks,

Ben

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2004-02-16 18:50
    Do you have to "probe" the circuit, or simply connect the logic probe?

    Does your circuit have an electrolytic (10uF or so) across the power and
    ground connection as well as a bypass (0.1 uF) across the same power terminals?
    I'm working circuit on circuit that works only when I have the logic
    probe connected to my supply voltage and ground. I'm guessing this is
    an obvious issue to someone with more experience then me.

    If someone could point me in the right direction I would be most
    appreciative.

    If more info is needed I can provide it.

    Thanks,

    Ben


    [noparse][[/noparse]Non-text portions of this message have been removed]
  • ArchiverArchiver Posts: 46,084
    edited 2004-02-16 19:10
    You probably do not have an input pulled up or down as necessary and
    therefore it is floating in 'no man's land'. When you connect the probe,
    you load the circuit down enough to bring the input into a less ambiguous
    region and then it works.

    Jim
    http://www.geocities.com/jimforkin2003/

    Original Message
    From: Ben Greenfield [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=g6BFbzKHilL5tHMq-q7sdABwHJGVGux0xvi0zv3bHIiQZq12NphxyRQg9hvdLZ-jVFHK]ben@c...[/url
    Sent: Monday, February 16, 2004 1:40 PM
    To: basicstamps@yahoogroups.com
    Subject: [noparse][[/noparse]basicstamps] amateur question about circuits


    Hello,

    I'm working circuit on circuit that works only when I have the logic
    probe connected to my supply voltage and ground. I'm guessing this is
    an obvious issue to someone with more experience then me.

    If someone could point me in the right direction I would be most
    appreciative.

    If more info is needed I can provide it.

    Thanks,

    Ben



    To UNSUBSCRIBE, just send mail to:
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  • ArchiverArchiver Posts: 46,084
    edited 2004-02-16 19:51
    On Feb 16, 2004, at 1:50 PM, smartdim@a... wrote:

    > Do you have to "probe" the circuit, or simply connect the logic probe?

    Just connect it, and it works.

    >
    > Does your circuit have an electrolytic (10uF or so) across the power
    > and
    > ground connection as well as a bypass (0.1 uF) across the same power
    > terminals?


    I found a barrel capacitor rated at 47 uF with a .1 uF both connected
    to the button that is not functioning.

    My next step is to replace those caps?

    Should I perform tests on the caps before doing this?

    Thanks,

    Ben


    >
    >
    > I'm working circuit on circuit that works only when I have the logic
    > probe connected to my supply voltage and ground. I'm guessing this is
    > an obvious issue to someone with more experience then me.
    >
    > If someone could point me in the right direction I would be most
    > appreciative.
    >
    > If more info is needed I can provide it.
    >
    > Thanks,
    >
    > Ben
    >
    >
    > [noparse][[/noparse]Non-text portions of this message have been removed]
    >
    >
    >
    > To UNSUBSCRIBE, just send mail to:
    > basicstamps-unsubscribe@yahoogroups.com
    > from the same email address that you subscribed. Text in the Subject
    > and Body of the message will be ignored.
    >
    > Yahoo! Groups Links
    >
    >
    >
    >
    >
  • ArchiverArchiver Posts: 46,084
    edited 2004-02-16 19:52
    On Feb 16, 2004, at 2:10 PM, Jim Forkin wrote:

    > You probably do not have an input pulled up or down as necessary and
    > therefore it is floating in 'no man's land'. When you connect the
    > probe,
    > you load the circuit down enough to bring the input into a less
    > ambiguous
    > region and then it works.


    That is what I was thinking I was curious as to what my be the failed
    part. It sounds like it may be the caps.

    Thanks,

    Ben
    >
    > Jim
    > http://www.geocities.com/jimforkin2003/
    >
    >
    >
    Original Message
    > From: Ben Greenfield [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=MxkSVzSpF6wQa1WwO0eVdctSEi7qdLYKCx2WV0ELflN-uSooPIZOKhJWRS5ibiPEUAc]ben@c...[/url
    > Sent: Monday, February 16, 2004 1:40 PM
    > To: basicstamps@yahoogroups.com
    > Subject: [noparse][[/noparse]basicstamps] amateur question about circuits
    >
    >
    > Hello,
    >
    > I'm working circuit on circuit that works only when I have the logic
    > probe connected to my supply voltage and ground. I'm guessing this is
    > an obvious issue to someone with more experience then me.
    >
    > If someone could point me in the right direction I would be most
    > appreciative.
    >
    > If more info is needed I can provide it.
    >
    > Thanks,
    >
    > Ben
    >
    >
    >
    > To UNSUBSCRIBE, just send mail to:
    > basicstamps-unsubscribe@yahoogroups.com
    > from the same email address that you subscribed. Text in the Subject
    > and
    > Body of the message will be ignored.
    >
    > Yahoo! Groups Links
    >
    >
    >
    >
    >
    >
    >
    > To UNSUBSCRIBE, just send mail to:
    > basicstamps-unsubscribe@yahoogroups.com
    > from the same email address that you subscribed. Text in the Subject
    > and Body of the message will be ignored.
    >
    > Yahoo! Groups Links
    >
    >
    >
    >
    >
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