Sounds like it depends if that meter uses LEDs for illumination, this is 'cause an LED will only flow current in one direction whereas an incandescent bulb doesn't care. If there's an LED in that meter then you'll want to follow Steve's wiring... I think those colors should be the same for you.


Nope, it shouldn't affect it at all. You're still flowing current only through the LEDs... If this were an issue that thread would have been full of people complaining about their coolant temp (or whatever) was off.

 

Does the sender use an amplifer box? That's the way mine is anyway, IIRC the amp box has it's own wiring that is seperate from the gauge face lights.

 

odd i did what mark said on my gauges and it worked...they dim

 

No, mine just has a single connector that plugs into the gauge. If there's any amp or anything it has to be inside the gauge itself.

My gauges have LEDs for illumination. Are yours bulb or LED?

 

LEDs on mine

 

Ok, I'll try it both ways and see what works. What wire did you tie the illumination in to for dimming? What gauges did you say you have?

I finished my first prototype DIN gauge panel tonight. It looks like it's going to work perfectly, and I may not even have to shave any material from the dash area around the stereo.

 

I have Autometer Z-Series in there.

 

What wire did you tie into for dimming? I'll give that a try and see what happens.

 

Ok, scrap the dimming idea. I finally pressured Autometer into letting me talk to someone who knows what they're doing. The black wire coming from the gauge shares the ground to the sender since the sender is a 2 wire setup. The ground in the gauge is common to power the lighting, sender, and gauge. Thus, if I hook it into the dimmer, it will cause the needle reading on the gauge to move with the dimmer. Bummer. Autometer sells a separate dimming device for these gauges, but then you're turning two knobs, one for the dash lights, and one for the Autometer gauges.

Mechanical gauges can be hooked into the dimmer, just not the full sweep electrics.

On a related note....Autometer can swap out the white back light in the SportComp II gauges for green to match the factory dash. It's $25 per gauge and takes 5-7 days. The bezel of the gauge is crimped on so there's no way to do it at home as a new bezel and lens is required.

I'm going to chew on that for a day or so, but I'm leaning toward having the illumination changed.

It sucks being so anal.

 

heh to be honest man i totally forgot where i wired it too been a long time since i have really worked in the Tacoma and i have also removed the gauges. If you are still working on it a couple weeks from now i can tell yea as im going to be working on the taco again.

 

Since the Autometer LED electric gauges can't be dimmed with the stock dimmer, I've been looking for another solution. Autometer offers a "dimmer" for their LED gauges. Here's it is:

http://www.autometer.com/cat_accesso...l.aspx?vid=185

The guys at Autometer said they don't know how it works, but that it's more than just a rheostat in a box (it better be for $29.99).

So I have a background in electronics, and thought I might try to just build one myself. I'm hoping one of you electronics guys can validate my thoughts here.

I found this timer chip:

http://www.uoguelph.ca/~antoon/gadgets/555/555.html

and this circuit with description:



Here is a 12 volt / 2 amp lamp dimmer that can be used to dim a standard 25 watt automobile brake or backup bulb by controlling the duty cycle of a astable 555 timer oscillator. When the wiper of the potentiometer is at the uppermost position, the capacitor will charge quickly through both 1K resistors and the diode, producing a short positive interval and long negative interval which dims the lamp to near darkness. When the potentiometer wiper is at the lowermost position, the capacitor will charge through both 1K resistors and the 50K potentiometer and discharge through the lower 1K resistor, producing a long positive interval and short negative interval which brightens the lamp to near full intensity. The duty cycle of the 200 Hz square wave can be varied from approximately 5% to 95%. The two circuits below illustrate connecting the lamp to either the positive or negative side of the supply.

Looks to me this can be easily built for about $5 in parts if I'm looking at this right. I've found the 555 timer chip at Radio Shack for $1.50 and the other parts for around $3. Mount it in a small black plastic project box and you're done.

Thoughts?

 

I think $30 isn't that much money... Time is money too you know, and it could be your time may be better spent elsewhere

I mean, if you were saving a couple hundred bucks I might say go for it; but only saving $25?

 

^ I have to agree with Brian,
I personally don't have the time to sit and work on something when that same time used to make the unit can be used to work in the shop and make extra $
but if you love that kind of stuff and have the extra time at home or whatnot then go for it!

 

I've spent a few hours on the gauges themselves to make everything perfect, but I don't have kids or anything so I have gobs of time and enjoy projects like this. I like to solve problems like these and I actually had to go back and do some trig and other math to figure out the gauge bezel and angle rings. I think you guys will be pretty surprised when you see the finished product.

A trip to Radio Shack and I could build this in about 30 minutes. I'm just wanting someone to verify my logic in the circuit, Midiwall?

I'm not even sure the gauges will need to be dimmed as I run my dash at full bright all the time anyway, but I wanted a backup plan in place just in case. I don't want to spend the time buttoning everything up then realize I should've gotten a dimmer.

 

Yeah, the schematic is generally correct... The "right" way to dim an LED is to use PWM which that circuit will do. The problem with the circuit is that it will toast your LEDs. Most common LEDs work on about a 3v forward voltage, that circuit goes to great lengths to hit 12v.

You can drop the source voltage to make the LED happy, but you'll need at least 7v or so to get the 555 working. Also, I really hate 555 - they were cool Way Back When, but... Well, actually, I'm just complaining, the noise that a 555 generates won't be an issue in this application.

But, that said.. here's another option.

http://radiolocation.tripod.com/LEDd...ampDimmer.html

Now, if you wanna get real crazy, I do LED dimmers using PICs. but that's WAY overkill for this, unless you wanna stuff a tri-color LED in there and do smooth fades between colors and such. I have code that'll get you 65k colors if you'd like!


Side note...

For those looking over our shoulder, the "easy" way to dim a lamp is to just reduce the voltage. that works "fine" if you're talking about a carbon filament bulb. But in a device like an LED, you have to keep the voltage above a certain level in order for the reaction to occur that causes light. So, you can dim it to a point, but then it just goes out.

So, what you do is use a "pulsed DC voltage" and vary the amount of time that the voltage is present. If you do this fast enough, then you get to play games with the "persistence of vision" and you stop seeing the pulses as individual ticks as they all blur together.

So, this is "PWM" (Pulse Width Modulation)... You're basically turning on a full 3v for a very short period. The longer you leave the voltage on, the brighter the LED will appear.

 

Fair enough

Being an ME, I got the XD-16; it has a photocell on the front of the gauge and auto-dims

 

HAHAHAHAHH!!!!!!!!

 

My DB gauge has a wire that connects to the stock dash lighting and dims when the lights come on...that one's not the problem. It's the Autometer gauges I'm trying to figure out.

You know my problem with the XD-16.....it's GINORMOUS!

 

The vehicles electrical system is 12V as you know. If the Autometer gauges are expecting 12V on the dimmer wire, shouldn't they already be setup to handle 12V? I'm sure they have the proper resistor in line. I mean if the Toyota dimmer was "normal' then I'd just be hooking the dimmer wire directly to the car's 12V dimmer. The only reason I'm having to manufacture a dimmer circuit is because Toyota adjusts the ground rather than the voltage.

I had previously reviewed the link you posted as well, however he looks for a worst case scenario voltage of 6V, which is half what the car is going to provide.

 

Ahh, then you're NOT planning to wire straight to the LED. I made a "leap of faith", sorry.

Okay, so there may be another problem here... As you say, the lamp circuit in the meter will be looking for 12v, but something has to be happening to drop the voltage to the LED. If it's just a resistor, then the 12v PWM will work, if it's fancier, like a 7805 or somesuch, then you'll run into trouble with the regulator not firing right on a PWM circuit - which in that case, you'd be back to looking to just drop the voltage/limit the current in order to pull off the dimming.

Any desire to open up the meter and see what they're doing in there?

Something that may give you a clue without opening the meter is to hook up the lamp wire straight to the electrical. Start the engine and see if the lamp brightness changes with engine speed (i.e., the alternator kicking into the 2nd level). If so, then the LED circuit is NOT regulated and a PWM or current limiter should work fine.