ATTN elec. Gurus, lighting/dimming question - Page 4

skivvie · 02-17-2004, 02:02 PM

Okay, my write up/how to is now up at Scoobymods. Give it a read over guys and let me know if there's anything that i should add or tweak. I hope i gave credit where it's due, but if i left anyone out let me know.

http://www.scoobymods.com/forums/sho...&threadid=3115

* Registered users of the site do not see these ads.

vrg3 · 02-17-2004, 02:56 PM

Great write-up, skivvie! Very nicely done. I added a link to it on my web page.

One thing I'd ask -- the title of the ScoobyMods post seems to imply this will work only with Omori gauges. Is it possible to change the title to read "Dim Aftermarket Gauges" instead of "Dim Omori Elec. Gauges?"

skivvie · 02-17-2004, 04:33 PM

Yeah, i thought about that. I did mention in the write up that it can be used for other gauges... i just went with Omori because i KNOW it works with Omori's and that seems to be the gauges most people ask about. But i agree... it might get more attention that way. Maybe i'll get them to change it to Dim Aftermarket Gauges (Omori, etc...) or something like that.

turboICE · 02-17-2004, 04:46 PM

Also the circuit is only necessary for gauges that do not provide a seperate ground wire for the LEDs. Any gauge that splits the LED and power ground does not need this mod - including for instance Omori mech gauges that only have an LED + and - .

Ed.

skivvie · 02-17-2004, 04:56 PM

Good point, i'll get them to add that. That's why i kept noting Omori ELECT. gauges. .. but i didn't specifically say Mech's didn't need it.

Moondongle · 02-17-2004, 06:49 PM

Where was this write-up a week ago when I was pulling out my hair!?!? I can't wait to try a new circuit again.

Great write-up skivvie. You might also want to mention that you can encapsulate the circuit in epoxy to seal it as well.

Thanks again VRG3 for designing the circuit.

vrg3 · 02-17-2004, 07:21 PM

Moondongle - A week ago? Skivvie just posted that on ScoobyMods today.

Skivvie - Why doesn't this apply to mechanical gauges? I'm using it on my mechanical boost gauge which has its bulb internally connected to its chassis. It is useful for any gauge that includes a dimmable light (which most all decent automotive gauges do) but don't allow you independent access to both sides of the light's power supply.

skivvie · 02-17-2004, 07:41 PM

I guess i need to be way more specific... it doesn't apply to Omori Mech gauges. =]

Moondongle: i had it done a week ago... i was just waiting to take a couple more photos before i posted it. Sorry! heheh.

I'll submit those changes to Kastle tonight. Thanks for the input guys. I'll probably also start a new thread pointing to the scoobymods.com post.

Moondongle · 02-17-2004, 08:20 PM

vrg3: I just could have used this a week ago. It would have saved an hour and a few fuses.

fliz · 02-18-2004, 04:12 PM

I just soldered the fix together last night. The instructions on Scoobymods were great!!!

I only have one question...

If I want to dim the lights with a resistor, what wattage do I need?

I have some 1/2 watt 2.2K resistors left from the EGT fix, but I'm afraid they are too small for this use. Does anybody know how much power the lights for 3 Omori gauges consume?

vrg3 · 02-18-2004, 04:23 PM

The way I recommend reducing brightness is by changing the voltage going to the noninverting (+) input of the op amp. That is, either increase the resistance between pins 3 and 7, or decrease the resistance between pins 3 and 4. If you do one or the other even a 1/8-watt resistor will be okay.

Try putting two of your 1/2-watt 2.2K resistors wired in series in place of the existing single 10k resistor between pins 3 and 4 maybe?

skivvie · 02-18-2004, 05:11 PM

So you'd recommend cutting the voltage on the + INPUT of the circuit rather than the + output side as i suggested in the write up?

I'll include that in the edit if you have good reason.

I suggested it the way i did because Omori supplies a little end cap that you can put in place of the color box which simply contains a 200 Ohm resistor in line with the + illum. input. I tested adding a 1/4 watt 2.2K resistor and it worked fine to dim the gauges closer to stock brightness, and didn't get warm.

aaronbooke · 02-27-2004, 12:07 AM

(Sorry if anyone gets this post twice)

I just got a 2002 Outback Sport and I pulled the factory stock CD stereo to put in a Blaupunkt Casablanca CD51. Everything seems to work fine, except for the dimmer/illumination function. When I turn the headlights on...or off...the Blau dims for about a half-second and then brightens again.

I don't care so much for variable dimming, but at least hi/low would be nice as that Blau is obnoxiously bright while driving out in the sticks at night.

I got what should be the official Blaupunkt-to-Subaru adapter connector from Tweeter, Etc...it did seem to have everything line up just right. Orange wire to orange wire and whatnot. If it matters, I did put a Radio Shack noise filter on the red (ignition 12V+) wire but not the yellow (constant 12V+) wire.

Is this a case of the Subaru-control-thru-ground issue? Will that circuit trick (very well documented and great pics, btw) solve the problem?

Thanks!
Aaron
Boston, MA

vrg3 · 02-27-2004, 12:17 AM

skivvie - Putting a resistor in series with the output of the circuit does indeed decrease the voltage and current that the gauge's bulbs get, but there are a couple disadvantages: The resistor then has to radiate all the power that's no longer going to the bulbs. The resistor size depends on the current draw of the gauges (It's conceivable that some gauges might not even draw any significant current, making this approach not work at all). And because it depends on the current draw, it'll change if you were to attach more gauges.

Changing the input voltage to the + input of the op amp simply changes the output voltage of the circuit, no matter what the load is. The power will still have to be radiated but the TIP31 has a built-in heat sink.

Aaron - That's weird that it dims for half a second and then goes back. That means it's not simply responding to the levels it gets. It'd help to have more info on what the head unit's supposed to do with its illumination input.

If all you need is for it to dim when the headlights come on you don't need anything special; the Illum+ wire (which should be what the orange wire on the harness was going to) has +12v when the lights are on and floats when they're off, just like on non-ground-switched cars.

aaronbooke · 02-27-2004, 02:36 PM

I may have figured why my Blaupunkt dims only for a second when I turn on my headlights. I finally got through to Blau tech support and they tell me that the radio (Casablanca CD51) is looking for 2VDC to 12VDC for dimming. When it's 0VDC, no dim occurs. When it's 2VDC, maximum dim occurs (about half the normal brightness, according to the tech) and then as voltage increases to 12VDC, the dimming amount decreases until at 12VDC there's no dim.

Now first off, this strikes me as a dumbass way to run a railroad, but moving on...

I think the Subaru is starting from OVDC and quickly ramping up to 12VDC whenever I turn on the lights, so the Blau sees the 2VDC and dims quick but then quickly undims as the Subaru gets up to 12VDC.

So now I have another question - does the Subaru vary the voltage at all on the orange illumination wire depending on what level of dim you've set? My hunch it that it doesn't, or else changing the dimmer would probably have SOME effect on the Blau (it might be in reverse, but it'd work). I suppose I'll have to pull out the Fluke voltmeter and have a look...but if anyone knows off the top of their head...

Regardless, does anyone have any suggestions on how I can get the 12VDC on that orange wire down to about 2 or 3VDC? I usually leave the dimmer adjustment set to max brightness anyway, so even just a hi/low dim on the Blau would be fine for me.

Thanks!
Aaron

vrg3 · 02-27-2004, 02:41 PM

The voltage on the orange wire isn't ramping from 0 to 12 volts. Certainly not over half a second, anyway.

The orange wire doesn't vary in voltage when you turn the rheostat. The other illumination wire (which was probably left out of your harness) does.

It sounds like it might work for you to build the circuit we've been talking about and feed its output into your head unit. You might need to play with the input voltage a little like skivvie and I are talking about.

Does the Blaupunkt head unit draw any current through its illumination input? If it doesn't, you could just use a resistive voltage divider to bring the voltage down.

skivvie · 02-27-2004, 04:48 PM

Quote:

Originally posted by vrg3

Changing the input voltage to the + input of the op amp simply changes the output voltage of the circuit, no matter what the load is. The power will still have to be radiated but the TIP31 has a built-in heat sink.

Ah, well put, well put. Makes sense. I gotta get around to getting Kastle to update my how to.

mhbrown · 03-15-2004, 08:16 PM

When people refer to dipping the circuit in epoxy, what kind of product exactly am I looking for? Specifically, what do I ask for at my friendly Home Depot?

vrg3 · 03-15-2004, 11:11 PM

Any kind of epoxy would do. I typically make a little square cup out of masking tape, place the circuit in it, and then pour in mixed 2-part epoxy like this stuff:

http://www.nuwavetackle.com/devcon9oz.jpg

After it sets you can peel off the masking tape.

You can also use epoxy gels, which aren't self-leveling:

http://www.g-bush.hu/gelepoxy.jpg

You can just smear the mixed gel all over.

Keep in mind that either of these types of epoxy will likely be a good insulator, so if you put them on the heat sink they'll prevent it from radiating heat. A hardware store probably won't carry it, but it is possible to find thermally conductive epoxy.

mhbrown · 03-16-2004, 07:22 AM

Thanks vrg. I built the circuit and installed it last night. Works like a charm on my 3 Omori gauges.

bringndefinition · 08-12-2004, 01:51 AM

I wonder if that dimmer circuit located on 04's can be found in the same place of 03's? can anyone confirm?

OCD · 03-10-2005, 07:58 PM

Well i hooked up the circuit as directed for the gauges and it worked fine but after about 5 mins it burned up. I am not sure whether somehow something shorted or whether I used to low of a watt resistor. I only used 1/4 watt resistors and i think that may have been my problem. Any suggestiosn? I am going to try and rebuild it with 1/2 watt resistors instead tomarrow and use epoxy gel when i finish it.

Dan

vrg3 · 03-11-2005, 10:39 AM

Even 1/8-watt resistors should be more than enough. Each of these resistors is radiating less than a hundredth of a watt.

Did you insulate the metal heat sink of the TIP31 from ground? It shouldn't be allowed to come into electrical contact with the car's chassis.

You didn't put a resistor in series with the output like skivvie said, did you?

OCD · 03-11-2005, 12:54 PM

Well I am going to build it again with the 1/4 just cause i bought both so I am going to use those this time, are you saying that the ground for the circuit can't be grounded to frame, cause thats what i did or are you saying the heat sink can't be grounded itself because that definitely wasn't. I didn't put a resistor in output either. I am using this on a VDO gauge so there was no need for that.

Dan

vrg3 · 03-11-2005, 01:53 PM

Sure, go ahead and try building it again, maybe a little more carefully just in case.

The circuit's ground can be grounded to the frame; that's no problem -- I was just talking about the heat sink.

It sounds like you did the right thing, so my guess is that it must have been some kind of intermittent short that caused the problem. Potting it in epoxy can help avoid those since it prevents anything in the circuit from moving relative to anything else.

Good luck.

02-27-2004, 12:07 AM	#88
aaronbooke Scooby Newbie Member#: 56050 Join Date: Feb 2004 Location: Boston, Massachusetts Vehicle: 2002 Outback Sport Red/Titanium	Related question (Sorry if anyone gets this post twice) I just got a 2002 Outback Sport and I pulled the factory stock CD stereo to put in a Blaupunkt Casablanca CD51. Everything seems to work fine, except for the dimmer/illumination function. When I turn the headlights on...or off...the Blau dims for about a half-second and then brightens again. I don't care so much for variable dimming, but at least hi/low would be nice as that Blau is obnoxiously bright while driving out in the sticks at night. I got what should be the official Blaupunkt-to-Subaru adapter connector from Tweeter, Etc...it did seem to have everything line up just right. Orange wire to orange wire and whatnot. If it matters, I did put a Radio Shack noise filter on the red (ignition 12V+) wire but not the yellow (constant 12V+) wire. Is this a case of the Subaru-control-thru-ground issue? Will that circuit trick (very well documented and great pics, btw) solve the problem? Thanks! Aaron Boston, MA

03-15-2004, 08:16 PM	#93
mhbrown Scooby Newbie Member#: 12537 Join Date: Nov 2001 Location: Cincinnati, Ohio Vehicle: '02 WRX Sportwagon WR Blue Pearl	Epoxy? When people refer to dipping the circuit in epoxy, what kind of product exactly am I looking for? Specifically, what do I ask for at my friendly Home Depot?

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02-17-2004, 02:02 PM	#76
skivvie Scooby Newbie Member#: 29719 Join Date: Nov 2002 Location: Draper, UT Vehicle: '06 WRX Wagon Silver	Okay, my write up/how to is now up at Scoobymods. Give it a read over guys and let me know if there's anything that i should add or tweak. I hope i gave credit where it's due, but if i left anyone out let me know. http://www.scoobymods.com/forums/sho...&threadid=3115 * Registered users of the site do not see these ads.

02-17-2004, 02:56 PM	#77
vrg3 Scooby Specialist Member#: 25796 Join Date: Oct 2002 Location: Cleveland, OH Vehicle: 2012 Impreza	Great write-up, skivvie! Very nicely done. I added a link to it on my web page. One thing I'd ask -- the title of the ScoobyMods post seems to imply this will work only with Omori gauges. Is it possible to change the title to read "Dim Aftermarket Gauges" instead of "Dim Omori Elec. Gauges?"

02-17-2004, 04:33 PM	#78
skivvie Scooby Newbie Member#: 29719 Join Date: Nov 2002 Location: Draper, UT Vehicle: '06 WRX Wagon Silver	Yeah, i thought about that. I did mention in the write up that it can be used for other gauges... i just went with Omori because i KNOW it works with Omori's and that seems to be the gauges most people ask about. But i agree... it might get more attention that way. Maybe i'll get them to change it to Dim Aftermarket Gauges (Omori, etc...) or something like that.

02-17-2004, 04:46 PM	#79
turboICE Scooby Specialist Member#: 33979 Join Date: Mar 2003 Chapter/Region: South East Location: Charlotte, NC Vehicle: 2006 STi WRB	Also the circuit is only necessary for gauges that do not provide a seperate ground wire for the LEDs. Any gauge that splits the LED and power ground does not need this mod - including for instance Omori mech gauges that only have an LED + and - . Ed.

02-17-2004, 04:56 PM	#80
skivvie Scooby Newbie Member#: 29719 Join Date: Nov 2002 Location: Draper, UT Vehicle: '06 WRX Wagon Silver	Good point, i'll get them to add that. That's why i kept noting Omori ELECT. gauges. .. but i didn't specifically say Mech's didn't need it.

02-17-2004, 06:49 PM	#81
Moondongle Scooby Newbie Member#: 39552 Join Date: Jul 2003 Chapter/Region: BAIC Location: Santa Cruz, CA Vehicle: 2003 WRX Wagon WRB	Where was this write-up a week ago when I was pulling out my hair!?!? I can't wait to try a new circuit again. Great write-up skivvie. You might also want to mention that you can encapsulate the circuit in epoxy to seal it as well. Thanks again VRG3 for designing the circuit.

02-17-2004, 07:21 PM	#82
vrg3 Scooby Specialist Member#: 25796 Join Date: Oct 2002 Location: Cleveland, OH Vehicle: 2012 Impreza	Moondongle - A week ago? Skivvie just posted that on ScoobyMods today. Skivvie - Why doesn't this apply to mechanical gauges? I'm using it on my mechanical boost gauge which has its bulb internally connected to its chassis. It is useful for any gauge that includes a dimmable light (which most all decent automotive gauges do) but don't allow you independent access to both sides of the light's power supply.

02-17-2004, 07:41 PM	#83
skivvie Scooby Newbie Member#: 29719 Join Date: Nov 2002 Location: Draper, UT Vehicle: '06 WRX Wagon Silver	I guess i need to be way more specific... it doesn't apply to Omori Mech gauges. =] Moondongle: i had it done a week ago... i was just waiting to take a couple more photos before i posted it. Sorry! heheh. I'll submit those changes to Kastle tonight. Thanks for the input guys. I'll probably also start a new thread pointing to the scoobymods.com post.

02-17-2004, 08:20 PM	#84
Moondongle Scooby Newbie Member#: 39552 Join Date: Jul 2003 Chapter/Region: BAIC Location: Santa Cruz, CA Vehicle: 2003 WRX Wagon WRB	vrg3: I just could have used this a week ago. It would have saved an hour and a few fuses.

02-18-2004, 04:12 PM	#85
fliz Scooby Guru Member#: 30342 Join Date: Nov 2002 Location: #blp	I just soldered the fix together last night. The instructions on Scoobymods were great!!! I only have one question... If I want to dim the lights with a resistor, what wattage do I need? I have some 1/2 watt 2.2K resistors left from the EGT fix, but I'm afraid they are too small for this use. Does anybody know how much power the lights for 3 Omori gauges consume?

02-18-2004, 04:23 PM	#86
vrg3 Scooby Specialist Member#: 25796 Join Date: Oct 2002 Location: Cleveland, OH Vehicle: 2012 Impreza	The way I recommend reducing brightness is by changing the voltage going to the noninverting (+) input of the op amp. That is, either increase the resistance between pins 3 and 7, or decrease the resistance between pins 3 and 4. If you do one or the other even a 1/8-watt resistor will be okay. Try putting two of your 1/2-watt 2.2K resistors wired in series in place of the existing single 10k resistor between pins 3 and 4 maybe?

02-18-2004, 05:11 PM	#87
skivvie Scooby Newbie Member#: 29719 Join Date: Nov 2002 Location: Draper, UT Vehicle: '06 WRX Wagon Silver	So you'd recommend cutting the voltage on the + INPUT of the circuit rather than the + output side as i suggested in the write up? I'll include that in the edit if you have good reason. I suggested it the way i did because Omori supplies a little end cap that you can put in place of the color box which simply contains a 200 Ohm resistor in line with the + illum. input. I tested adding a 1/4 watt 2.2K resistor and it worked fine to dim the gauges closer to stock brightness, and didn't get warm.

02-27-2004, 12:17 AM	#89
vrg3 Scooby Specialist Member#: 25796 Join Date: Oct 2002 Location: Cleveland, OH Vehicle: 2012 Impreza	skivvie - Putting a resistor in series with the output of the circuit does indeed decrease the voltage and current that the gauge's bulbs get, but there are a couple disadvantages: The resistor then has to radiate all the power that's no longer going to the bulbs. The resistor size depends on the current draw of the gauges (It's conceivable that some gauges might not even draw any significant current, making this approach not work at all). And because it depends on the current draw, it'll change if you were to attach more gauges. Changing the input voltage to the + input of the op amp simply changes the output voltage of the circuit, no matter what the load is. The power will still have to be radiated but the TIP31 has a built-in heat sink. Aaron - That's weird that it dims for half a second and then goes back. That means it's not simply responding to the levels it gets. It'd help to have more info on what the head unit's supposed to do with its illumination input. If all you need is for it to dim when the headlights come on you don't need anything special; the Illum+ wire (which should be what the orange wire on the harness was going to) has +12v when the lights are on and floats when they're off, just like on non-ground-switched cars.

02-27-2004, 02:36 PM	#90
aaronbooke Scooby Newbie Member#: 56050 Join Date: Feb 2004 Location: Boston, Massachusetts Vehicle: 2002 Outback Sport Red/Titanium	I may have figured why my Blaupunkt dims only for a second when I turn on my headlights. I finally got through to Blau tech support and they tell me that the radio (Casablanca CD51) is looking for 2VDC to 12VDC for dimming. When it's 0VDC, no dim occurs. When it's 2VDC, maximum dim occurs (about half the normal brightness, according to the tech) and then as voltage increases to 12VDC, the dimming amount decreases until at 12VDC there's no dim. Now first off, this strikes me as a dumbass way to run a railroad, but moving on... I think the Subaru is starting from OVDC and quickly ramping up to 12VDC whenever I turn on the lights, so the Blau sees the 2VDC and dims quick but then quickly undims as the Subaru gets up to 12VDC. So now I have another question - does the Subaru vary the voltage at all on the orange illumination wire depending on what level of dim you've set? My hunch it that it doesn't, or else changing the dimmer would probably have SOME effect on the Blau (it might be in reverse, but it'd work). I suppose I'll have to pull out the Fluke voltmeter and have a look...but if anyone knows off the top of their head... Regardless, does anyone have any suggestions on how I can get the 12VDC on that orange wire down to about 2 or 3VDC? I usually leave the dimmer adjustment set to max brightness anyway, so even just a hi/low dim on the Blau would be fine for me. Thanks! Aaron

02-27-2004, 02:41 PM	#91
vrg3 Scooby Specialist Member#: 25796 Join Date: Oct 2002 Location: Cleveland, OH Vehicle: 2012 Impreza	The voltage on the orange wire isn't ramping from 0 to 12 volts. Certainly not over half a second, anyway. The orange wire doesn't vary in voltage when you turn the rheostat. The other illumination wire (which was probably left out of your harness) does. It sounds like it might work for you to build the circuit we've been talking about and feed its output into your head unit. You might need to play with the input voltage a little like skivvie and I are talking about. Does the Blaupunkt head unit draw any current through its illumination input? If it doesn't, you could just use a resistive voltage divider to bring the voltage down.

03-15-2004, 11:11 PM	#94
vrg3 Scooby Specialist Member#: 25796 Join Date: Oct 2002 Location: Cleveland, OH Vehicle: 2012 Impreza	Any kind of epoxy would do. I typically make a little square cup out of masking tape, place the circuit in it, and then pour in mixed 2-part epoxy like this stuff: http://www.nuwavetackle.com/devcon9oz.jpg After it sets you can peel off the masking tape. You can also use epoxy gels, which aren't self-leveling: http://www.g-bush.hu/gelepoxy.jpg You can just smear the mixed gel all over. Keep in mind that either of these types of epoxy will likely be a good insulator, so if you put them on the heat sink they'll prevent it from radiating heat. A hardware store probably won't carry it, but it is possible to find thermally conductive epoxy.

03-16-2004, 07:22 AM	#95
mhbrown Scooby Newbie Member#: 12537 Join Date: Nov 2001 Location: Cincinnati, Ohio Vehicle: '02 WRX Sportwagon WR Blue Pearl	Thanks vrg. I built the circuit and installed it last night. Works like a charm on my 3 Omori gauges.

08-12-2004, 01:51 AM	#96
bringndefinition Scooby Newbie Member#: 25197 Join Date: Sep 2002 Location: SF Vehicle: 2003 Subaru Wrx Black	I wonder if that dimmer circuit located on 04's can be found in the same place of 03's? can anyone confirm?

03-10-2005, 07:58 PM	#97
OCD Scooby Specialist Member#: 40710 Join Date: Jul 2003 Location: Cortlandt Manor, NY Vehicle: 2005 SILVER EVO ULTIMATE COLLISION CENTER	Well i hooked up the circuit as directed for the gauges and it worked fine but after about 5 mins it burned up. I am not sure whether somehow something shorted or whether I used to low of a watt resistor. I only used 1/4 watt resistors and i think that may have been my problem. Any suggestiosn? I am going to try and rebuild it with 1/2 watt resistors instead tomarrow and use epoxy gel when i finish it. Dan

03-11-2005, 10:39 AM	#98
vrg3 Scooby Specialist Member#: 25796 Join Date: Oct 2002 Location: Cleveland, OH Vehicle: 2012 Impreza	Even 1/8-watt resistors should be more than enough. Each of these resistors is radiating less than a hundredth of a watt. Did you insulate the metal heat sink of the TIP31 from ground? It shouldn't be allowed to come into electrical contact with the car's chassis. You didn't put a resistor in series with the output like skivvie said, did you?

03-11-2005, 12:54 PM	#99
OCD Scooby Specialist Member#: 40710 Join Date: Jul 2003 Location: Cortlandt Manor, NY Vehicle: 2005 SILVER EVO ULTIMATE COLLISION CENTER	Well I am going to build it again with the 1/4 just cause i bought both so I am going to use those this time, are you saying that the ground for the circuit can't be grounded to frame, cause thats what i did or are you saying the heat sink can't be grounded itself because that definitely wasn't. I didn't put a resistor in output either. I am using this on a VDO gauge so there was no need for that. Dan

03-11-2005, 01:53 PM	#100
vrg3 Scooby Specialist Member#: 25796 Join Date: Oct 2002 Location: Cleveland, OH Vehicle: 2012 Impreza	Sure, go ahead and try building it again, maybe a little more carefully just in case. The circuit's ground can be grounded to the frame; that's no problem -- I was just talking about the heat sink. It sounds like you did the right thing, so my guess is that it must have been some kind of intermittent short that caused the problem. Potting it in epoxy can help avoid those since it prevents anything in the circuit from moving relative to anything else. Good luck.