Dimming prosport gauges

So I have been reading up on these gauges and I have a question. I have just bought an amber/white mechanical boost guage. I would like to only use the white function but have it dim when the lights are on. From my research on here it seems that this gauge will have 4 wires (black, red, white, amber). I know the ground is black. The red is to be hooked up to acc power. The white and amber control the light color.

 

Someone also mentioned that the white and amber wires do not directly feed the lights in the gauge, just act as inputs. This means that adding a resistor into this line would have no effect. Some have tried adding a resistor into the red line but there was fear this would effect the gauge reading.

 

My question is, since this is a mechanical gauge, can I control the backlight brightness by adding a resistor into this line without affecting the accuracy of the gauge?

 

If I can I will set up a simple relay circuit to switch the feed on the red wire with the lights. When the lights are off the red wire would get straight 12V but when the lights come on the relay would switch to add a resistor into the line and reduce the voltage.

I know this is 6 months late, but for anyone searching (like me) and curious about this, how did it go? I'm installing a prosport electric boost gauge, and am curious.

hmm I have a friend who has them, Im gunna see him tonight so ill ask

Hmm I'm sure you can give it a try on the input side.. I only hooked up the white myself.. don't want the orange at night. If it's a mechanical gauge of course it has no effect if there's power or not. Don't know about the electrical gauge however..

I emailed prosport about this... will post if/when he responds.

The answer is this:

 

You can dim the gauges by using something such as a relay as the switch. That relay would switch between a circuit with a resistor and one without, as mentioned above.

 

The display is LED, so they are tough to dim (tending to either be on or off with small changes in resistance). My thought is to use a variable resistor, dial in the dimmed brightness, and then just tuck it away and be done with it.

 

You want to have this resistor in the WHITE wire for white display always on (no amber). The ilumination is in fact powered by the white and orange wires, not by the red power wire, so that's what you tap.

 

I have no time for this unfortunately, maybe next month, but definitely give it a shot.

 

BTW this is what Ryan said at Prosport. Good luck.

I did try this by hooking up a variable pot but had no luck. Like ^^ said, they are very touchy to resistance. I couldn't get the gauge to dim reliably. With the slightest touch to the pot the gauge would tweak between on and off with a small amount of dimming.

 

I ended up just hooking it up to turn red with the headlights on. This did lead to a new problem though. Since our cars let you leave the headlights on when you turn the car off if you turn it on with the headlights one the gauge will see both 12V signals at the same time and get stuck in the white/red setting regardless of the headlights. What I need to do is add a delay in the 12V feed from the headlight circuit so that the gauge will see the 12V from the ignition first and then the headlights. I have not figured this out yet and have just dealt with this quirk.

I have mine set up on a single pole double throw switch such that when the car is on (no head lights) they display white, then when I switch the head lights on it drops out the white and goes red. the SPDT is what keeps them from seeing both 12v signals that gets it "stuck". Thus I can toggle back and forth without getting "stuck".

 

A little late, but I also tried a pot to dim them and it does not work.

 

fyi: http://legacygt.com/forums/showthread.php?t=72301

Could you elaborate on how it gets "stuck"? If I have ACC (white) go on first, and illumination (orange for me) go on second, what's the issue? Thanks!

If you have them sequence like that then you are fine. The problem comes when both come on at the same time. This happens when the headlight switch is on and the car is turned on. The gauge won't change to orange then.

 

I think a relay that cuts off the ACC power when the headlights come on should correct this though. I may have to experiment a little.

The only way to reliably "dim" leds for this type of application is with Pulse Width Modulation. Basically the leds blink at variable rates to simulate brightness. http://cgi.ebay.com/25-watt-PWM-Driver-Dimmer-KIT-fits-all-Leds-even-Luxeon_W0QQitemZ360176062216QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item53dc2a8f08&_trksid=p3286.c0.m14

 

I have one of the above boards and they work great with leds. I have not tried it yet with my Prosport gauge but I'm confident it will work.

i have this exact gauge, and mine works like this

 

turn ign on with lights on, it stays white.

 

turn ignition on with lights off, than gauge is amber, until i turn the headlights on.

 

dont completely understand the logic of it, but I spent waay too much time trying to figure it out. It works, so im happy

The only way to reliably "dim" leds for this type of application is with Pulse Width Modulation. Basically the leds blink at variable rates to simulate brightness. http://cgi.ebay.com/25-watt-PWM-Driver-Dimmer-KIT-fits-all-Leds-even-Luxeon_W0QQitemZ360176062216QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item53dc2a8f08&_trksid=p3286.c0.m14

 

I have one of the above boards and they work great with leds. I have not tried it yet with my Prosport gauge but I'm confident it will work.

 

I'm not an EE, so question: is this the best thing to buy to try to dim the prosport, or is there a better similar alternative on ebay or elsewhere? I can solder and all, just don't mind spending $20 instead of $10 to have this thing dim.

I like this board over some other units because of its size. It's extremely simple to assemble: if you can install prosport gauges you can certainly assemble the PWM kit. There are others on ebay that come complete but they have housings which take up a lot more space. Just make sure to stay away from variable resistance type devices. PWM is the way to go with leds.

just ordered one