[Diy_efi] pulse readings: correction.
Karl Walter
krw at efn.org
Sat Feb 26 19:09:13 GMT 2005
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Hello,
The LED needs an 800 ohm balast resistor for 5 volt pulses.
I am sorry for not providing accurate information in my previous post. =
I just figured it was a nice opportunity to share a "quick trick" I =
use.=20
W.S. Cowell seems to think my post was "misleading" and "nonsense" =
Does everybody else on the list feel this way too? I usually give the =
E-mails a quick read, and I have been hesitant to post something that's =
not a question. I just threw out an idea, brainstorm style, and now I =
feel that I should not post unless I have a guarenteed, tested, and 100% =
accurate answer. =20
To All, should I be afraid to post replys to this list? Do you want =
to read my sometimes not fully thought out ideas, or should I just shut =
up? Threads don't stay around long usually, So if a quick answer that =
might be wrong isn't OK, I probably won't be able to get a reply off =
before the origional question is long gone.
Jim wrote:
"Hey all, I tried to check the pulses comming on that tach signal but =
to my dispise the fluke multi meter I have does not read HZ... any cheap =
and easy ideas???"
He was looking for "ideas" and yes, he seems to be asking for a hz =
reading.
A loud speaker won't give a quantative frequency reading either, =
although I may have missed a previous post by Jim, explaining exactly =
what he was doing.
The loudspeaker, as suggested by David is a great Idea. If a tiny =
plastic enclosed Piezo tweeter will work, it would be tough enough to =
coexist with all the wrenches in my tool box without being crushed. I =
would be a great addition to my collection of quick and easy diagnostic =
tools.=20
Here's the details on using an LED as a quick diagnostic tool:
Some user's results may be different due to differences in LED's. I =
can provide specs on the LEDs I have used, but it's easier to just try =
some.
An led on a 5 volt pulse will require a dropping resistor. Use 800 =
ohms. 2 LED's with dropping resistors, one forward biased, one reverse, =
in parallel, avoids a mistake in polarity. For the ignition refrence =
pulse on a GM DIS system (1990 3.1l v6) at Idle the LED will seem almost =
steady, but look carefully, you can see the flicker. =20
Super bright LED's work better. An 800 ohm resistor works well, it =
shows nicely on 5 volts, and won't blow the LED if connected to 12v for =
a few seconds or more.
Just a simple LED, no resistor, does work to check a vehicle speed =
sensor, or a crank position sensor, as long as it is the 2 wire reluctor =
style, not a Hall effect unit. I have done this on GM crank sensors, =
and gm and ford VSS's, and it works surprisingly well.
I wouldn't suggest that this is a substitute for a lab scope or other =
quantitative instrument, but having some LED's in your tool kit on the =
road, or at the wrecking yard can be really handy. A vss can be checked =
by just spinning it by hand, a crank sensor, by waving a =
(steel)screwdriver by it. On the road, if your car quits, you can =
determine if the 5 volt Ignition reference pulse is present while =
cranking, but the loud speaker would be better since it wouldn't require =
two people, one to crank and one to watch.=20
--Karl
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<HTML><HEAD>
<META http-equiv=3DContent-Type content=3D"text/html; =
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<META content=3D"MSHTML 6.00.2800.1106" name=3DGENERATOR>
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<BLOCKQUOTE=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV><FONT face=3DArial size=3D2>Hello,</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>The LED needs an 800 ohm balast =
resistor for 5=20
volt pulses.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>I am sorry for not providing accurate =
information=20
in my previous post. I just figured it was a nice opportunity to =
share a=20
"quick trick" I use. </FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>W.S. Cowell seems to think my post =
was=20
"misleading" and "nonsense" Does everybody else on the list feel =
this=20
way too? I usually give the E-mails a quick read, and I have been =
hesitant to=20
post something that's not a question. I just threw out an idea,=20
brainstorm style, and now I feel that I should not post unless I have =
a=20
guarenteed, tested, and 100% accurate answer. </FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>To All, should I be afraid to post =
replys to this=20
list? Do you want to read my sometimes not fully thought =
out=20
ideas, or should I just shut up? Threads don't stay around long =
usually,=20
So if a quick answer that might be wrong isn't OK, I probably won't be =
able to=20
get a reply off before the origional question is long =
gone.</FONT></DIV>
<DIV> </DIV><FONT face=3DArial size=3D2>
<DIV><BR>Jim wrote:</DIV>
<DIV> </DIV>
<DIV>"Hey all, I tried to check the pulses comming on that tach signal =
but to=20
my dispise the fluke multi meter I have does not read HZ... any cheap =
and easy=20
ideas???"</DIV>
<DIV> </DIV>
<DIV>He was looking for "ideas" and yes, he seems to be asking for a =
hz=20
reading.</DIV>
<DIV> </DIV>
<DIV>A loud speaker won't give a quantative frequency reading =
either,=20
although I may have missed a previous post by Jim, explaining exactly =
what he=20
was doing.</DIV>
<DIV> </DIV>
<DIV>The loudspeaker, as suggested by David is a great Idea. If a tiny =
plastic=20
enclosed Piezo tweeter will work, it would be tough enough to coexist =
with all=20
the wrenches in my tool box without being crushed. I would be a great =
addition=20
to my collection of quick and easy diagnostic tools. </DIV>
<DIV> </DIV>
<DIV>Here's the details on using an LED as a quick diagnostic =
tool:</DIV>
<DIV> Some user's results may be different due to differences in=20
LED's. I can provide specs on the LEDs I have used, but it's =
easier to=20
just try some.</DIV>
<DIV>An led on a 5 volt pulse will require a dropping resistor. Use =
800=20
ohms. 2 LED's with dropping resistors, one forward biased, one =
reverse,=20
in parallel, avoids a mistake in polarity. For the ignition =
refrence=20
pulse on a GM DIS system (1990 3.1l v6) at Idle the LED will seem =
almost=20
steady, but look carefully, you can see the flicker. </DIV>
<DIV><BR>Super bright LED's work better. An 800 ohm resistor works =
well, it=20
shows nicely on 5 volts, and won't blow the LED if connected to 12v =
for a few=20
seconds or more.</DIV>
<DIV> </DIV>
<DIV>Just a simple LED, no resistor, does work to check a vehicle =
speed=20
sensor, or a crank position sensor, as long as it is the 2 wire =
reluctor=20
style, not a Hall effect unit. I have done this on GM crank =
sensors, and=20
gm and ford VSS's, and it works surprisingly well.</DIV>
<DIV> </DIV>
<DIV>I wouldn't suggest that this is a substitute for a lab scope or =
other=20
quantitative instrument, but having some LED's in your tool kit on the =
road,=20
or at the wrecking yard can be really handy. A vss can be =
checked by=20
just spinning it by hand, a crank sensor, by waving a =
(steel)screwdriver by=20
it. On the road, if your car quits, you can determine if the 5 =
volt=20
Ignition reference pulse is present while cranking, but the loud =
speaker would=20
be better since it wouldn't require two people, one to crank and one =
to watch.=20
</DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV>--Karl<BR></FONT></DIV></BLOCKQUOTE></BODY></HTML>
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