Rheostat for Gauges?

[AK6LPSD]

I have 4 autometers with the optional blue LED bulbs. They are way to bright compared to the dash. I have them tied into the factory dimmer but the dash lights are too dim to see when the gauges are dimmed.

I was thinking of adding a rheostat to the illumination wire of the gauges to "turn them down" to the same level as the dash.

Looking for some help from the electron guru's here. I found a rheostat at <font color="red"> Radio Shack</font>. It is rated 25-Ohm 3-Watt variable resistor. Would this work with the 4 led's, if not what is your advice?

[PSD PAC]

I would put an inline fuse holder (buss type) on your setup, then start trying a few different resistors. Once you set on the resistor, you can probably just leave it in place (or solder it for security); that way you'll have it tied in to your dash dimmer without having to fuss with multiple rheostats.

If you use that one from radio shack, it should do fine - 3 watts is more than enough to handle those LEDs, and 25ohm should be enough to get you plenty of dimming.

Just my 2c...and worth every penny?

[Ford_Forgotton]

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3 watts is more than enough to handle those LEDs, and 25ohm should be enough to get you plenty of dimming.


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25ohms isnt enough. You wouldnt even notice it.

Bob riley at Dieselsite.com has a variable resistor just for the LED gauges like the cobalts.

Or you can get a 0-10k potentiometer from radio shack. Would be cheaper and instant gratification.

[AK6LPSD]

[ QUOTE ]
25ohms isnt enough. You wouldnt even notice it.

Bob riley at Dieselsite.com has a variable resistor...Or you can get a 0-10k potentiometer from radio shack.

[/ QUOTE ]

Thanks, I emailed dieselsite.com for the specs on their dimmer.

Help me out here, more ohms is more resistance hence more dimming in this case? So why would a 25K ohm rheostat be too small and a 10K ohm potentiometer be better? They are both variable resistors just wired slightly different. Do I have it backwards and the smaller number ohms is more resistance? Yeah, I feel like a retard but at least Im not in denial. I checked Radio Shack, they have 16 potentiometer's rated anywhere from 1MW to 100K for less than $3 each.

I kinda like the resistor in the fuse holder idea also. It makes sense if I could find a resistor that would equalize the gauges with the dash. I wouldnt' know where to start on what size resistor?

[Ford_Forgotton]

[ QUOTE ]

Help me out here, more ohms is more resistance hence more dimming in this case? So why would a 25K ohm rheostat be too small and a 10K ohm potentiometer be better?

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Ahh, see, there was no "K" in the original post. I thought you actually had a 25 OHM, not a 25k Ohm. Yes, larger is more resistance.

[AK6LPSD]

No you're right, my bad. You just gave me the deer in the headlight look...I just went back and checked the rheostat is 25ohm. [img]/ubbthreads/images/graemlins/crazy.gif[/img]

[Ford_Forgotton]

I hate that. You think life is going along just peachy, and then someone says something really simple and time just stops and you go "Oh Crap". well, not crap, but you get the idea [img]/ubbthreads/images/graemlins/laugh.gif[/img]

Yeah, 25 ohms isnt gonna be enough. Something between 2k and 10k should knock them down nicely tho.

I had to use 5.6k's on my LEDs in my door switches to get them down to a useable level.

[AK6LPSD]

I read your LED stuff awhile ago and looks really nice. Maybe someday I will takle it. I been meaning to get the dieselsite coolant filter so I might order it and the dimmer from them after they get back to me on the specs of the dimmer. Thanks for your help.