Aw,man. This thread sounds SO much like Vacuum 101
it's incredible! LOL!
Let me clarify my intent: I was wanting to go across a
voltage source (across MDS signal and ground) with my
LED and resistor,which are in series. The higher the
value of the resistor,the less chance it will affect
the MDS signal.
My circuit would be a series circuit,but the
connection to the vehicle would be parallel.
Steve P.
--- "Bernd D. Ratsch" <bernd@dodgetrucks.org> wrote:
>
> Which ISN'T why you'd want the resistance as high as
> possible. Signal
> circuits are very picky on what you add to them.
> Just be careful and don't
> go overboard (such as a customer who fried his
> Cluster out with too many
> LED's in his cab)- $900 mistake, or Best Buy tapping
> into the wrong wire at
> the PCM and frying out an injector control circuit
> and an injector - $1100
> mistake.
>
> - Bernd
>
> -----Original Message-----
> From: Jason Bleazard [mailto:dml@bleazard.net]
> Sent: Sunday, February 03, 2008 10:49 AM
> To: dakota-truck@dakota-truck.net
> Subject: Re: DML: MDS "on" LED...
>
>
> Bernd D. Ratsch wrote:
> >
> > Just make darn
> > sure you don't ground the signal circuit - PCM
> goes "bye bye".
>
> Which is exactly why you want the resistance of an
> added circuit to be
> as HIGH as possible.
>
> It actually depends on whether you're adding things
> inline to an
> existing circuit, or creating a new circuit in
> parallel. Going inline,
> you want the resistance to be as small as possible
> so you don't affect
> the existing circuit. If you're adding a new
> circuit in parallel, you
> want the resistance to be as large as possible.
>
> It sounds like Steve is thinking of adding a new
> circuit in parallel for
> his LED. That would make more sense. If it was
> inline, then all the
> current that goes through the existing circuit would
> drive through the
> LED, which probably isn't what he wants. Who knows
> how much current
> goes through that line, it might be too much or too
> little to drive the
> LED. If he tries to change the resistance to keep
> the LED happy then it
> won't make the PCM happy.
>
> Now, if he adds a parallel circuit for the LED it's
> easier. There's
> currently no LED circuit there, and an open circuit
> (or one that doesn't
> exist) is infinite resistance. It therefore pulls
> zero current. You
> want to keep it as close to the current situation as
> possible. Keep the
> resistance as high as possible while still
> illuminating the LED, which
> will make sure it draws the bare minimum current
> that it needs.
>
> I wonder if a low-power relay would pull even less
> current than an LED.
> Steve, if you're feeling ambitious, that might be
> worth investigating.
> Hook up the relay input in parallel, then use the
> output to drive the
> LED circuit and completely avoid connecting the LED
> to the PCM.
>
> If you add a new low-resistance circuit, it adds a
> large current draw.
> Zero resistance (i.e. a "short") is what lets the
> magic smoke out of the
> parts. Remember, V=IR.
>
> --
> Jason Bleazard http://drazaelb.blogspot.com
> Burlington, Ontario
> his: '95 Dakota Sport 4x4, 3.9 V6, 5spd, Reg. Cab,
> white
> hers: '01 Dakota Sport 4x4, 4.7 V8, Auto, Quad Cab,
> black
>
>
>
>
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