[Gmecm] Shift light load

[bcroe at juno.com]

You ought to be able to put a resistor in parallel with 
the LED to keep leakage current from building up 
enough votage to turn the LED on.  A couple 1N4004s 
in series with the LED could increase the threshold 
voltage req'd to turn on the LED, while allowing a 
higher value resistor in parallel with the combination 
to absorb leakage current.  You still need a resistor 
in series with the source, to limit "on" current.  

The latest high efficiency LEDs can put out a LOT of 
light (but rather directionally) with very little current.  

Bruce Roe

5 May 07  "JohnsHome" <JohnsHome at wideopenwest.com> writes:
> LEDs work nice on a quad output when used with the right resistor.
> The only thing is that the leakage current will keep the LED dimly 
> lit.
> Not a big deal but you may want to fiddle with resistors to get the 
> best
> dim/bright settings.
> John
> 
> > -----Original Message-----
> > From: gmecm-bounces at diy-efi.org 
> [mailto:gmecm-bounces at diy-efi.org]On
> > Behalf Of Rob Handley
> > Sent: Saturday, May 05, 2007 9:42 AM
> > To: gmecm at diy-efi.org
> > Subject: Re: [Gmecm] Shift light load
> >
> >
> > Thanks Scott.
> >
> > I'm going to a car show tomorrow - so shall have a look out for
> > ultra bright
> > LED fittings.
> >
> > Robin
> >
> > ----- Original Message -----
> > From: "Scott Peitzsch" <jlg-sep at comcast.net>
> > To: <gmecm at diy-efi.org>
> > Sent: 03 May 2007 21:47
> > Subject: Re: [Gmecm] Shift light load
> >
> >
> > >A typical dash indicator bulb - shift light or otherwise - is 
> going to be
> > > either a 194 or a 168, which will consume 0.27 - 0.35A.  The 
> other
> > > typical device those quad driver outputs control are vacuum 
> solenoids
> > > and relays, which generally check in around 60 ohms (at least 
> the few
> > > I have here to measure), which is a sinking load of ~200mA.
> > >
> > > If I had to guess, I'd say those drivers have to be good for 
> sinking
> > > at least an amp.  However, I'd probably consider using a relay 
> much
> > > above 500mA just to be conservative.
> > >
> > > Have you looked into any of the ultra bright LEDs?  You can get 
> the
> > > brightness you want without the penalty of hugely increased 
> current
> > > consumption.  In fact, you'd probably end up drawing LESS than 
> you
> > > do today.  I've used these in the past:
> > >
> > > http://www.autolumination.com/
> > >
> > > -Scott
> > >
> > >
> > >> Anybody know what load can be put on the shift light pin of a 
> '727?
> > >>
> > >> I'm using a small dash light ATM, but it's not wonderfully
> > visible so I
> > >> was thinking of fitting something bigger and higher wattage -
> > as long as
> > >> it doesn't fry the ECM!
> > >>
> > >> Robin
> > >
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