[Diy_efi] help w/dyi-wb please

[bcroe at juno.com]

A tail light is not a very good test, and not even good for 
the WB circuit.  Run the 5 ohm/10 ohm resistor test from 
the web site. 

With the sensor hooked up, the voltage across R4 should 
start at 1.25 volt and stay there for about 45 sec.  Meanwhile
the voltage across the heater (J1 to J2) should slowly rise 
to about 10.4 volts in that time.  At 10.4 volts the LED should 
come on.   

If the R4 voltage decreases from 1.25V before the heater 
reaches 10.4 volts, your power supply is not delivering 14 
volts.  

If R4 continues to read 1.25 V, but the heater never reaches 
10.4 volts (or requires much more than 45 seconds), you
need a little more current to your heater.  Put one or several 
15 ohm 1/4 watt resistors in parallel with R4 to boost 
it a little.  

If you take minutes to turn on, the circuit is on the 
edge of dropping out all the time.  You should see  
some decrease in voltage across R4 in the next minute
after the LED turns on.

I haven't run destructive tests on high buck sensors, but 
recomendations are not to leave it in the running exhaust 
when not powered.

Bruce Roe

On Thu, 2 May 2002 18:52:33 EDT JMSMAUTOMOTIVE at cs.com writes:
> i just compleated my first "trial" dyi-wb board. i have 
> tried to test the heater circuit with a tail lamp bulb and 
> also the o2 sensor, the result is the same, no led. with 
> the bulb hooked up, it slowly comes on, and stays on, 
> bright, indefinatelly, and the led will not light. my hunch 
> is that i need to add a resistor or two in parrallel with 
> r4 as stated in the assembly guide.  my problem is 
> that i ordered all the parts from digikey, and i have no
> idea what kind of resistor to add. the dyi-wb web page 
> doesn't specify what kind of resistor to use. my other 
> question has to do with using the sensor, in the assembly 
> guide it states that if the led goes out at any time to 
> remove the sensor from the exaust stream or damage 
> may occur, why?? does it hurt the sensor to be in the 
> exhaust stream without being @ temp? or is it just that 
> rapid cooling may crack the internal structure? i plan on 
> using this to tune many cars, so it would be nice to know 
> what ,how ,and why damage  can be caused. thanks joe 

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