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Discussion Starter · #1 ·
I'm installing 5 autometer gauges in my el camino. I want to use an adjustable resister to vary the internal gauge lights. Should the lights be wired in series or parallel? I don't want to use/overload the stock light switch. Thanx.
 

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Discussion Starter · #3 ·
Thank you John, i appreciate the info. I did a search, but that didn't show. I'm gonna tie the wiper connection to the 12V input connection, then take output from the third terminal. Does that sound about right?
 

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Could just tie the lights to the IGN terminal but again they will be on every time the car is running.
 

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Discussion Starter · #5 ·
I meant
the wiper on the variable resistor tied to the power connection side of the resistor. The output to the lights runs from the other side of the variable resister. This way I can vary light intensity.

Ultimately, power does come from the IGN post in the fuse box. I have a wire from the IGN post to the control terminal of a relay. Then the output of the relay feeds the gauges & their lights.
 

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If you get a potentiometer with an off position you will be able to turn them off during the day. There's 2 basic kinds of pots: linear taper and audio taper. Has to do with resistance increase through the pot travel. Look for something that's a linear taper pot. It will dim more evenly. Don't forget about the pot's current rating.
 

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Where are you getting the potentiometer? The little 2W dial jobs you can get at electronics places probably won't cut it.

You have to find a very low resistance, high power potentiometer. I don't know what the stock switch dimmer resistance is but I'd bet it's no more than about 5 ohms. It also looks to be about 10 or 20 watts.

You have to know the resistance of all the bulbs when on. The best way would be to measure the current draw and the supplied voltage to calculate the resistance. Then, find a pot about 5x the resistance. The power rating has to be calculated for a pot resistance = to the bulb resistance.

If you've installed these autometer guages then you've probably removed some of the origional dash equipment and therefore, the origional dash bulbs. If this is the case, I really don't see a problem with wiring the new guage bulbs in their place.

Peter
 

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Discussion Starter · #8 ·
Peter
You are right. I realized (once I started syphering my ohms law) that the 3 watt (25ohm) pot from Radio Shack was not gonna hack it. The bulbs in the 5 gauges are about 7-7.5 ohms. The last real electronics supply store in this city has closed and www.partsexpress.com doesn't carry anything suitable. I'll go with an on-off switch for now. Thanx.
 

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I run 8 gauge lamps from the original wire feed for the stock Lamp system.

I run them in parallel, as shown in the above referenced picture. That is: Each (+) between lamps is one node, and each (-) is tied to the same ground node.

-Got it wrong until Peter poked me with a stick. :D

I can still use my stock light-switch to vary brightness.

Should your stock rheostat not be working well, try some "electric spray cleaner" in small amount and actuate (twist quickly) the brush over the coil. Helps make a better contact.

Use the LMPS post if need be. Jsut one more female spade sticking out of the fuse box.

;)
 

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Originally posted by Peter F.:
The picture does not show a series connection. If you series the bulbs they won't light.

Peter
Sweet mother of pearl!
I can't believe I just got that wrong.
I need to be shot.


I'll fix it, and start drinking less.
 

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Which picture Peter? I know Elree's diagram doesn't clearly show the series connections on the lights but otherwise it's correct.
 

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A series connection is when you connect the parts so the same current flows through all of the devices. For example, take a bunch of lights with 2 wires coming out of them. You connect one wire of the first light to the +ve and the other wire to one wire of the next light. Then the other wire of that light to the next light. And so on. Last wire goes to the -ve.

A parallel connection is when you connect all of the parts with one terminal to the +ve and one to the negative.

How the wires are pysically routed to achieve the connection has no influence on describing it as a series or parallel connection.

O = bulb

series;
+---O---O---O---O----

negative terminal is last - at right


Parallel;

+-----
| | | |
OOOO
| | | |
------
^
this - is the negative terminal.

I'd do better pictures but HTML doesn't seem to allow for double spaces in the document. Hopefully you get the idea.

Peter
 

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Think I'll just stick to the word chained to describe hooking up a series of items. Maybe I won't sound confusing.
 

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Peter.

use: "code" your text "/code"


</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">series
(+)----(B)-----(B)------(B)-----B(-)

or

Parallel
(+)
|__________
| | |
| | |
(B) (B) (B)
| | |
| | |
|----------
(-)</pre>[/QUOTE]Sorry, felt compelled to redeem myself.
 
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