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Power up problem. — Parallax Forums

Power up problem.

ArchiverArchiver Posts: 46,084
edited 2002-04-19 12:50 in General Discussion
Hi guys, I have a BasicStamp 2 that I'm using as a converter
for an automotive sensor prototype. The Stamp recieves pulse width
modulated data and converts it to ASCII then sends to a laptop.
IF the power to the laptop is present before the STAMP power
then the Stamp doesn't run. If the Stamp is powered first everything
is fine. Any help???
I assume I'll need an isolated driver or something like that...
Part numbers?? Schematics??

Thanks,
Gary

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2002-04-17 17:59
    Apparently no one else has ever had this problem????

    --- In basicstamps@y..., "histatmac" <gary.shelton@h...> wrote:
    > Hi guys, I have a BasicStamp 2 that I'm using as a converter
    > for an automotive sensor prototype. The Stamp recieves pulse width
    > modulated data and converts it to ASCII then sends to a laptop.
    > IF the power to the laptop is present before the STAMP power
    > then the Stamp doesn't run. If the Stamp is powered first everything
    > is fine. Any help???
    > I assume I'll need an isolated driver or something like that...
    > Part numbers?? Schematics??
    >
    > Thanks,
    > Gary
  • ArchiverArchiver Posts: 46,084
    edited 2002-04-18 16:55
    Maybe you could share your stamp program?

    Leroy

    histatmac wrote:
    >
    > Apparently no one else has ever had this problem????
    >
    > --- In basicstamps@y..., "histatmac" <gary.shelton@h...> wrote:
    > > Hi guys, I have a BasicStamp 2 that I'm using as a converter
    > > for an automotive sensor prototype. The Stamp recieves pulse width
    > > modulated data and converts it to ASCII then sends to a laptop.
    > > IF the power to the laptop is present before the STAMP power
    > > then the Stamp doesn't run. If the Stamp is powered first everything
    > > is fine. Any help???
    > > I assume I'll need an isolated driver or something like that...
    > > Part numbers?? Schematics??
    > >
    > > Thanks,
    > > Gary
    >
    > To UNSUBSCRIBE, just send mail to:
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    >
    >
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  • ArchiverArchiver Posts: 46,084
    edited 2002-04-19 01:12
    Hi Gary,

    Try something like this:
    http://focus.ti.com/docs/prod/productfolder.jhtml?genericPartNumber=TL7705B

    This is a voltage supervisor with a programmable delay that you could use as
    a "reset" to the stamp. The part is available in PDIP if you are opposed to
    surface mount devices. You can get samples from TI or buy from Digi-Key
    (p/n 296-3242-5-ND)

    Tom

    Original Message
    From: "histatmac" <gary.shelton@h...>
    To: <basicstamps@yahoogroups.com>
    Sent: Wednesday, April 17, 2002 11:59 AM
    Subject: [noparse][[/noparse]basicstamps] Re: Power up problem.


    > Apparently no one else has ever had this problem????
    >
    > --- In basicstamps@y..., "histatmac" <gary.shelton@h...> wrote:
    > > Hi guys, I have a BasicStamp 2 that I'm using as a converter
    > > for an automotive sensor prototype. The Stamp recieves pulse width
    > > modulated data and converts it to ASCII then sends to a laptop.
    > > IF the power to the laptop is present before the STAMP power
    > > then the Stamp doesn't run. If the Stamp is powered first everything
    > > is fine. Any help???
    > > I assume I'll need an isolated driver or something like that...
    > > Part numbers?? Schematics??
    > >
    > > Thanks,
    > > Gary
    >
    >
    > 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.
    >
    >
    > Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
    >
    >
  • ArchiverArchiver Posts: 46,084
    edited 2002-04-19 06:24
    Hi Gary,

    When a system locks at power up, the problem is often a phenomenon
    called SCR latchup. The outside source (your laptop) turns on first
    and drives a large current (>~20 ma) into an input pin of the Stamp
    (i.e. an input pin on the PIC chip on the stamp). The Stamp stays
    locked when you apply power to it. No function. Bad. Also possibly
    damaging if the current is too too high.

    The simple fix for this problem is to put a resistor between the
    source (the laptop) and the Stamp chip input, to limit the current to
    10 milliamps or less. A 470 ohm resistor is usually sufficient.

    Maybe that is the problem. Could be something else.

    -- Tracy

    (P.S. Probably everyone in EE has been bitten by this problem at one
    time or another. FYI, the lockup is actually a side effect of the
    construction of integrated circuits, the substrate diode, which at
    high currents becomes a "silicon controlled rectifier", with positive
    feedback that keeps it in a locked state. )

    >Apparently no one else has ever had this problem????
    >
    >--- In basicstamps@y..., "histatmac" <gary.shelton@h...> wrote:
    > > Hi guys, I have a BasicStamp 2 that I'm using as a converter
    > > for an automotive sensor prototype. The Stamp recieves pulse width
    > > modulated data and converts it to ASCII then sends to a laptop.
    > > IF the power to the laptop is present before the STAMP power
    > > then the Stamp doesn't run. If the Stamp is powered first everything
    > > is fine. Any help???
    > > I assume I'll need an isolated driver or something like that...
    > > Part numbers?? Schematics??
    > >
    > > Thanks,
    > > Gary
  • ArchiverArchiver Posts: 46,084
    edited 2002-04-19 12:50
    Thanks Tracy, I'll try the limiting resistor. Makes sense.
    Gary


    --- In basicstamps@y..., Tracy Allen <tracy@e...> wrote:
    > Hi Gary,
    >
    > When a system locks at power up, the problem is often a phenomenon
    > called SCR latchup. The outside source (your laptop) turns on
    first
    > and drives a large current (>~20 ma) into an input pin of the Stamp
    > (i.e. an input pin on the PIC chip on the stamp). The Stamp stays
    > locked when you apply power to it. No function. Bad. Also
    possibly
    > damaging if the current is too too high.
    >
    > The simple fix for this problem is to put a resistor between the
    > source (the laptop) and the Stamp chip input, to limit the current
    to
    > 10 milliamps or less. A 470 ohm resistor is usually sufficient.
    >
    > Maybe that is the problem. Could be something else.
    >
    > -- Tracy
    >
    > (P.S. Probably everyone in EE has been bitten by this problem at
    one
    > time or another. FYI, the lockup is actually a side effect of the
    > construction of integrated circuits, the substrate diode, which at
    > high currents becomes a "silicon controlled rectifier", with
    positive
    > feedback that keeps it in a locked state. )
    >
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