Hi Ross,
Would your Zener Diode idea serve to replace that line voltage
stabiliser that's supposed to ensure reliable and accurate reports by the
fuel gauge?
I ask, because the gauge reads about 3/8 tank low, the stabiliser is
new, and the WS manual says to test for 10v, with special equipment.
Would a Zener Diode provide a constant 10v?
BTW, I estimated that the life of the 7.5v bulb would be about 1/10 of
the rated-at-7.5v life of 1000 hrs. How does that compare to your
calculations?
Bob
On Fri, 21 Nov 1997 19:14:49 -0800 Ross MacPherson
<arm@unix.infoserve.net> writes:
>At 07:46 PM 11/21/97 EST, you wrote:
>>These bulbs are rated 200 mA at 7.5 volts.
>>_ If _ W = A * V, then W = 1.5A when .2A * 7.5V
>>The 12v bulbs I removed had markings of 2.2 and 3.0 W.
>>IF my formula for W = AV is correct, then there isn't much difference
>in
>>current.
>>Someone who knows electric theory is invited to participate in this.
>>Electricity is not my first love, and I'm trying to perfect a
>hydraulic
>>lightbulb to get away from the stuff entirely.
>>Bob
>>
>>
>Bob's on the right track here but if you carry Ohm's law a little
>further
>you'll find that the power consumption is doubled but the life of the
>lamps
>will be reduced exponentially. If any one wants an explanation e-mail
>me
>privately. It all boils down to: If you use the 7.5 V lamps they'll
>be
>brighter but they won't last as long. We all new that any way, right?
>
>Someone ( I forget who, sorry) mentioned using a resisitor to clamp
>the
>applied voltage to these lamps at @ 10 volts to keep them from burning
>out
>too soon. DON"T do this! You'll negate any improvement in brightness
>because the resistor would be in the circuit at all rheostat settings
>and
>you introduce a very small space heater to the under dash area as the
>resistor tries to dissipate the power no longer available at the lamps
>as
>heat . Also the calculated R value will change drastically if a lamp
>burns
>out. A Zener diode circuit could be bodged together for a couple
>bucks
>that'll do the same thing but without the risk of losing your smoke
>and will
>work with one lamp or ten.
>
>Cheers,
>
> Ross MacPherson
> 1947 MG-TC 3528
> 1966 MGB-GT
>
>
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