Re: Need resistor help please (35w x 12v)

On Sun, 19 Feb 2006 13:52:18 +1100, Franc Zabkar
<fzabkar@xxxxxxxxxxxxxxxxx> put finger to keyboard and composed:

On 13 Feb 2006 14:27:49 -0800, "Locu" <loculogic@xxxxxxxxx> put finger
to keyboard and composed:

Ahh, good point on the light striking surface and turning into heat.. I
hadn't thought of that.. pretty futile maneauver except perhaps to
spread the heat a little i guess.

Well, I installed HID (xenon) lights in my non-xenon equipped vehicle.
The projectors are designed for xenon's though, just it didn't come w/
that option. I bought an OEM kit, and everything is there, except the
stock wiring doesn't support the high amp load the startup of the HID's
draw which can be upwards of 100watts I understand. So I used the
existing wiring to a relay, to turn on/off my wiring harness which
brings power direct from the battery thru fuses to the HID lights.

Now since I bypassed the cars internal wiring, the car see's no light
bulbs in there, so it complains.

I'd suggest modifying the device that monitors the lamps, assuming it
is accessible from a maintenance point of view.

Let's assume this device works by monitoring the voltage drop in a
series resistance by means of a comparator, as follows:


BAT+ O--+- Rsense --+-O O---- 55W lamp ----O BAT-
| |
|___ ___|
| |
__|____|__
\ /
\ Comp /
\ /
\ /
\/


In this case you could remove the sense resistor and transfer it to
the new, heavier gauge, relay switched lamp circuit, as follows:

+= Rsense ==+
BAT+ O==+= Rsense ==+=O O==== 100W lamp ====O BAT-
| |
| |
O O

O O
| |
|___ ___|
| |
__|____|__
\ /
\ Comp /
\ /
\ /
\/

To maintain the same voltage drop for a 100W lamp as for the original
55W one, just use the equivalent of two identical sense resistors in
parallel. Doing it this way might only require a cheap 5W Al-clad
resistor.

Another approach is to leave the original resistor within the
monitoring device and add a second resistor to the heavy gauge
harness. The downside is that the current would then be shared between
two paths. To avoid disturbing the module, you may be able to
determine the value of the internal resistor by metering the BAT and
LAMP OUTPUT pins.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
.

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