When I first took out my boat for a night cruise I found the instrument cluster so bright that I actually had to drape a towel over the dash to be able to navigate. Since that cruise, I looked at a number of different solutions - swapping out the 194 bulbs for dimmer bulbs, adding colored bulb covers, switching to dimmer LED bulbs, even using fingernail polish to paint part of the bulbs. I finally decided to try and setup a dimmer to control the brightness of the existing bulbs.

Took a trip to the local radio shack, and picked up a 5W rheostat - the largest wattage that they had. I believe it was 25 Ohm. They only had about 6 to choose from. The rheostat's are 3 pin, which surprised me, for some reason I expected a two pin arrangement.



After doing a little internet based research (the radio shack guys were clueless), I learned that in my application I should use one of the outer pins (didn't matter which) and the inner pin. Found an old (168?) bulb laying about, so rigged up a test circuit - the rheostat worked well. It didn't dim all the way to 'off' but took the single bulb from bright to dim. I initially tested the rheostat on the negative side after the bulb, and then just for the heck of it, tried it on the hot side before the bulb. Both methods had the same effect.

Knowing from the wiring schematics that Four Winns daisy chains the power connections to the instrument lights, I decided to pull the instrument lights lead from the fuse panel and reinstall with the rheostat between them and give it a try. Well, I found that I was not able to tap in at the fuse panel as that circuit is also for the navigation lights. In fact, with the exception of the depth gauge, all of the instrument lights are toggled on/off by the nav light switch. I decided not to dim the nav lights.

Here's the helm:



I wanted the rheostat/dimmer to control the instrument lights for the 4 gauges to the right, but not the depth finder on the left which already lights up in red and is powered separately. As you can see from the pic, the Faria gauge package in my boat has the white faces. When lit with clear 194 bulbs, they are way too bright. I tied the rheostat into the circuit just before the point where it feeds into the tachometer, at the beginning of the daisy chain. The following night I was delighted to find that the rheostat could control the instrument lights from full on to full off. Almost perfect. But not quite, I still had the issue with the recessed light bar below the gauges to illuminate the push switches. I tried the rheostat on them with no luck, I understand some LEDs can be dimmed, and some can't. After brainstorming a bit I tried placing some old brake light repair tape I had on hand the following weeked. The resulting red light was acceptable, but the taping over the bars looked like (censored) in daylight. I ended up pulling the light bars, wrapping them with the brake light repair tape, and resinstalling.

Here you can see the starboard strip taped.



Back to the rheostat, I elected to mount it out of view. In the pic of the Helm above, you can see the Clarion head unit by looking through the steering wheel. Under the dash directly below that headunit, I mounted this panel.



On the panel there is an oversized white knob (the rheostat dimmer control), and a black contour switch (on the remote amp power line, turns off an amp, two speakers and subwoofer leaving the stock stereo intact). Note that the white oversize knob is something I had on hand, many different knobs are available, some of the old automotive dash light style knobs would work too.

Now the only light that bothers me is from the Clarion head unit! I must be more finicky than most people about retaining night vision. Of course the lakes where we boat do get very dark at night. The amount of stars in view can be incredible, last weekend we saw three 'shooting stars', and around a dozen satellites while out on a night cruise. Anyway, I'm still working on a solution for the Clarion, but thought the rheostat solution could be applied to a greater range of boats.

That is actually not a rheostat, but a potentiometer. The difference is that a rheostat has two leads, and a potentiometer has three.

In a rheostat, one lead, for the lack of a better term - is the "stator", and the other lead is the moving contact. In a pointometer, one lead is on each end of the stator, with the center lead in the moving contact. But the main thing is that if it has two pins, its called a rheostat, and if it has three (or more) its called a potentiometer.

A potentiometer can sometimes substitute for a rheostat, but not the other way around. However, it is quite often that a rheostat is "wire-wound" and has a higher current capacity as it is used primarily for higher current use as dimming lights or slowing down motors, and a potentiometer usually has a carbon path, and is used for lower current applications, such as a volume control.

However, there is some overlap, in that a 5Watt potentiometer is a bit uncommon, and may indeed be wire-wound. In that case, there is no reason you cannot use it for a potentiometer within its current handling parameters.

One advantage to a potentiometer is that if you use the center pin and one outside pin, the increase of resistance will be clockwise, but if you use the center pin and the other outside pin, the increase of resistance will be counter-clockwise. So in reality, there can be a bit more flexibility in using a potentiometer.

Sometimes, you may see a potentiometer having its center pin and one end pin soldered together to make a rheostat out of it.

But again, there is one issue. Potentometers come in one of two tapers - linear and audio, while rheostats come in liner taper only.

A liner taper means that if you move the dial to the 25% position, the resistance will be 25%, when the dial is at 40%, the resistance will be 50%, and so on. But in an audio taper, there is a logarmithic relationship between the resistance and rotation of the shaft. These are explicitly used for such things as audio volume controls wherein the signal level is not linear, but logarmithic.

If an audio taper is used for a non-audio application, you will have little change for most of the rotation, but a huge change for the rest of the rotation. Vice-versa for using a linear taper for a volume control.

Quite possibly more than you wanted to know, but there it is. By the way, check out www.mouser.com or www.allied.com for a huge selection of electronic components. This is where I buy most of my stuff.

By the way, I know of no LED that cannot be dimmed. But some LEDs are not LEDs at all, but rather integrated circuits. One example is a "flashing" LED. It contains not only the LED, but circuitry to allow the led to flash as well. Some of these "functional" LEDs may not be able to be dimmed.

Check this guy's solution to LED dimming. Complicated, but sounds like it is do-able.

LED dimming

In the old days of stereo's you could connect the lighting control to your lights so the stereo would dim. Actually, I don't think you had a choice. Depended on the unit you got.

Nowadays, I believe the lighting circuit is wired in with the power. Of course you can't lower the voltage to the unit to lower the lights.. Don't know what kind of unit your's looks like, but, sometimes you can get a cover for them. Don't know if they still make em tho. Might still be out there, they were for people who didn't have the removeable faceplates and wanted to cover up the stereo..

Don't go to Radio Shack if you can help it.. They don't carry what they used too for those who work on their own stuff..It's pretty limited nowadays.

Cool project tho. Haven't turned my lights on in my,new to me, boat as of yet. Something to keep in mind.. Thanks for the idea

Great project Jim! I don't have the ability tp dim my helm lights and thought many times of this same project, now you've given me a clue as to how to go about doing it.

Thanks for sharing.

Check with clarion as your head unit may be able to be wired such as fish n toss states. It also may have a dimmer switch/button built in. Similar to when you turn your headlights on in your car, your stereo dims. It would not surprise me that it is on there and not hooked up.

It may not work with the potentiometer, but you might be able to wire it in to the Nav lights so when you turn the lights on, the stereo dims.

Thanks for the comments and corrections! I do appreciate the info on potentiometers versus rheostats.

On the remaining 'light pollution', here's a pic of the source unit.



It is the display window that is too bright. Ironically Clarion touts this as a feature - "Bright white LED illumination." It'd probably not be a problem if the source unit was not installed at the helm. As it is, there are no separate power feeds for the LED, and the only menu adjustment is for contrast, which is to correct text contrast for one's viewing angle in daytime use, when the LED illumination does not come into play.

I have temporarily placed (red) brakelight repair tape over the display, which works well to dim the display at night, but this interferes with daylight viewing. As a temporary measure I apply it for night cruises and pull it off during the day. With all of this applying and removing, understandably the tape is starting to curl. At best a temporary fix to a minor irritant. Probably the best fix would involve opening up the source unit to get at the led.

Use it as an excuse to upgrade to the CMD5...

I looked at the CMD5 features when it first came out. The big differences I saw were a wireless remote, and support for MP3/WMA CD-Rs. Not enough to get me to switch. Out of curiosity I just did a quick scan of the CMD5 owner's manual, and wouldn't you know it, it does have a menu driven dimming feature. Ironically enough, "Bright White LED illumination" is not listed as one of the 'features' of the CMD5, as it was with the CMD4a.

Guess I'll start saving my pocket change, or maybe ask Santa for one for X-mas.

For what its worth, I am looking at having to upgrade my stereo head unit as well because it won't work with the iPod adapter.

Problem is, I don't think the new Sony systems are as good as the ones made 5 years ago. Sony better shape up or I am going to dump them and go with another brand.

My real dilemma is that I really like how I have the stereo system setup. Here is a link I did for You Tube showing it. Sorry for the poor quality of the video, but I am "roughing it" this week (staying on the boat).

http://www.youtube.com/watch?v=O_D7WY4xwo4

Sure it has some bling, but don't we all need a bit of bling in our lives?

Finally! The "Al Channel" on Youtube! I've been hoping for this.

Technology can be a scary thing.

Al, you might be able to keep your existing unit if you go bluetooth. Clarion offers a bluetooth add on for any head unit that has AUX input jacks, Clarion BLT370, and it works with the Clarion Bluetooth Audio Transmitter and Cradle for iPod (Clarion DLG370). I'm told that most of the CeNet iPod interfaces are very limiting in menu navigation, and play list access. I hear most owners end up navigating and select playlists from the tethered iPod itself, with this combo the control is maintained at the iPod, and the tether is through BT.

*edit - Neat Youtube video! I really like the way that drink holder with detachable coaster pops out of the source unit.

Thanks for the lead Jim.

If I could flush-mount it, that would have been an option.

One other issue I have is my receiver is pre-sat control, so I am using a stand-alone XM receiver, and it is using the line input jacks, so I would also have to rig up a switch - which would not be that hard to do.

I think I'll suffer through the system for the rest of the year, and figure out what I want to do next spring.

I am kind of leaning towards Alpine if I change out the system completely.

I already bought one of these though:



Its a flush-mount docking station for iPod, with adapters for virtually all of the varous kinds, including the iPhone.

That flush mount iPod docking station looks nice! Now that I look closer at the Clarion bluetooth adapters for iPod, I see it's a sleeve with a dongle. I thought they were just sleeves which would essentially turn the iPod iteslf into a 'remote'. I see where you are going, just slide the iPod in and access it like a cd changer.