[Diy_efi] DIY-WB construction & testing... help

[Andrew Brownsword]

>>on 7/18/02 2:27 PM, rr at RRauscher at nni.com wrote:

Thanks for responding in my time of need.   :)

>> The UEGO circuit fails two tests:  pin 5 of U3 measures 7.2v instead of 7.8
>> - 8.0, and J5 measures 1.8v instead of 1.9 - 2.1.
> 
> For U3 pin 5 lift one leg of the cap C12 and re-measure. IF the voltage
> goes up that cap is leaky.

The voltage didn't change, so the capacitor would seem to not be the
culprit.  Any other suggestions?  Is it related to the J5 voltage problem?
 
> J5 should really be closer to 2 volts. Is the +4 volt (VGnd) measurement
> on the low side? This would contribute to a low J5 reading. If not then
> double check the resistors R31, R32 & R35; as to being 1% to and 10K &
> 100K.

The VGnd voltage is about 3.95v -- so it is on the low side.  Could this be
a result of my power supply being on the 12.5v?  Does it matter?  Those 3
resistors are all very close to their target values (<0.5% error).
 
>> When I power on the heater circuit the LED doesn't come on.  The site says I
>> need 13-16 volts and the (R/C model) battery I'm using is only 12.5v -- is
>> this likely the reason?  When I measure the voltage across the LED it seems
>> to read -11.5v which makes me wonder if I put the LED on backwards, but I've
>> got the flat spot opposite the stripe on the PCB which is how the
>> construction guide indicates it should be.
> 
> If this is w/o the sensor or any load connected then the 12 V is enough
> to light the LED. Hmm, I thought that the flat went w/the stripe. Let'me
> check. . . Yes, the board I looked at has the LED flat on the same side
> as the footprint stripe end.

I reversed it and now it works fine.  I had it backward because this page
http://www.aces.edu/~gparmer/efi/temp/wb/guide.html says:

"The cathode (+) is identified by end having the stripe , a "+" marking, or
a longer lead. Also notable is that the LED has a flat spot machined on side
of the lens corresponding to the anode (-). On the schematic, the cathode is
the base of the triangle and the anode is the straight bar with the triangle
pointing at it. Notice that the cathode (+) being identified by a stripe is
a theme repeated on the circuit board (even for diodes like the LED which
are not identified this way). If the leads have already been cut on your
LED, look inside the diode. You'll notice two hunks of metal. The larger is
the anode."

Which, as I read it anyhow, implies that the flat spot is anode and the
stripe is cathode... meaning that the flat spot is away from the stripe.
What am I missing?

 
> P.S. note that the checks #34+ are not entirely valid. If they work OK,
> If not then do not worry about it.

I'm following this:  http://www.diy-wb.com/diywbchk.htm  and my browser
doesn't show any sensible test numbers... which one is #34, and should I
even bother trying them if they aren't entirely valid?  Hooking up the
switch sounds like a bit of a pain.


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