[Vwdiesel] Marks LED GP cct works...update-confirmed !

Smith, Michael Michael.Smith at rvh.nb.ca
Fri Dec 31 12:31:43 EST 2004

With 2 complete GP's(lightbulbs) and 2 blocking diodes, it works too ! YAY
for Mark !
An interesting feature, is, if you choose your components and wiring
carefully (creatively?) you can actually monitor
the GP's in action, rather than waiting for them to cycle, then have the
LED's pop on full brightness.

IE: I am just using "junk box" parts mostly (hams all have one of these) and
1 of the LED's I am using actually flashes ever-so-briefly when power is
first applied, then glows very very dimly (good for those early Canadian
mornings when it's 30C below and dark as the inside of a cow inside your
car) while the GP's are heating. The other LED I am using does not......you
might be able to fiddle with the ballast resistor value a little and/or the
choice of LED's you are using.

Alternately, you could control the LED's independant of the GP's entirely.
IE: test the GP's (with very low low current, thus not draining your
precious resources in your battery) even BEFORE you touch the ignition
switch !

Ideas, ideas....so many ideas........Just heard from my shop....they have my
winter tires ("tyres" for Mark) mounted and a BIG battery installed in the
LOTS of more repairs needed early in the new year before I get the $100
Bondo Golfy on the road, but hey, nothings free in life.  That's why we're
all here trying to keep our old diesels on the road in the first place

Mike in NB (@ work)
P.S.- I just had a thought.  If anyone was worried about the voltage drop on
the blocking diodes, you could get a couple HD 20A DPDT relays and wire them
in such a way as to switch the blocking diodes OUT of the actual feed wire
while the glowplugs are working, then switch them back IN when just testing
with the low current LED "test" circuit.
. . . . . . the possibilities are endless.

> -----Original Message-----
> From:	vwdiesel-bounces at vwfans.com [SMTP:vwdiesel-bounces at vwfans.com] On
> Behalf Of Smith, Michael
> Sent:	Friday, December 31, 2004 1:02 PM
> To:	'vwdiesel at vwfans.com'
> Subject:	[Vwdiesel] Marks LED GP cct works...I think
> Mark et al, 
> I found a few minutes to wire up your circuit here on the bench and using
> just a light bulb (instead of a real glow plug) and
> some hookup wire, an LED (with 1k resistor in series) a big battery and a
> biga$$ blocking diode, I got your cct to work.
> Whether this will work in situ, I can't say 100% for sure, but it sure
> looks
> promising.
> Here's how it worked for me (at about the 2 Amp level and only 1
> LED....and
> 1 lightbulb(GP)
> Turn ignition switch on....GP's come on and heat. (no LED's) 
> Timer kicks in (out?) and GP's turn off.....4 LED's come on as soon as
> GP's
> go off indicating you have good GP's.
> LED's will STAY ON, so you will need to rig up a switch to turn them off,
> as
> ultimately current is going through your
> GP's all the time. admittedly it's pretty low milliamp levels, but
> whatever,......
> I haven't yet had time to rig up a parallel cct with another bulb(GP) and
> a
> 2nd blocking diode, but so far don't see any problems.
> Will report any future findings to the list.  Email Mark the Miser (or me)
> for the .jpg diagram of his cct.
> I am thinking a small toggle switch running a 4Pole relay to control all 4
> LED's at once instead of 4 toggles.
> Mike in NB (@ work)
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