WBO2 testing

[bcroe at juno.com]

Measure the voltage across the lamp, and across the
1 ohm resistor.  If the lamp has less than 10 volts (and
the LED is out), you are probably running in the curent
limiting warmup mode.   The resistor will measure 
about 1.25 volt in that case.  

You probably are using too large a lamp.  With a small
voltage drop across the lamp and maximum current, you
have a large voltage drop (at max current) across the 
LT1086.  This heating it up, apparently to the point of
thermal shutdown which dims the light.

I would find a smaller bulb, which should run at 10 V
with reduced voltage across the 1 ohm (crossover to
voltage regulation).  A 2" by 3" heatsink is not very 
generous for this application, unless it has a lot of fins.

Bruce Roe 

On Mon, 17 Dec 2001 01:04:09 -0500 Glen Beard <gbeard1 at nycap.rr.com>
writes:
> OK, I've gotten everything soldered up, and I am testing the
> heater circuit using a tail lamp.  The lamp turns on nice
> and bright building its current to 1.003 Amps.  Is the LED
> supposed to turn on after a while?  Is the LT1086 (VR)
> supposed to get sizzling hot even with a 2x3" Al heat sink? 
> With the smaller heat sink I had on it, the bulb would light
> up and then start to dim again.  If I blew across it and it
> got brighter.

> Glen Beard 

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