Matching factory gauges

[Thomas S]

Originally Posted by rjb

I am currently working with Paul at Marshall to figure out the best way to build and market these dimmer switches as they will need PCB boards manufactured, and I will need to be able to do a minimum quantity to recoup the setup costs. I will keep everyone posted.

I've been doing a little research on my end with one of the gauges. The first thing I learned was that you must connect the +12V line. Just wiring to the orange wire and ground will not turn on the light in the instrument.

Having determined that, I wired the red wire to +12V and a variable voltage power supply to the orange wire. One would assume that cranking up the voltage slowly on the orange wire should gradually light up the gauge, right? Wrong! The light goes from off to full on at about 7.5 Volts and doesn't get any brighter as you crank the voltage higher.

Just for fun, I switched the red and orange wires so that the variable was on the red wire and the +12V on the orange wire. Then, as I cranked up the voltage on the red wire I could see the light flicker to life at about 7 Volts. As I cranked the voltage higher it gradually got brighter all the way to full on at 12 Volts. Not what I expected, but maybe good enough to work with the signal off the dimmer. I haven't gotten into that yet, so I don't yet know what the dimmer feeds to the OEM dash lights.

For you electronics geeks (like me), I suspect that some sort of interface circuit may be required to get the gauge lights to track with the dash lights. There are multiple ways to approach this problem, but maybe something as simple as an op-amp with gain and offset (to be determined) would do the trick. A brute force approach would be to digitize the output of the dimmer switch and use that to drive the address bus of a PROM lookup table driving a DAC followed by an op-amp to supply voltage for the gauge lights.

That all sounds like a lot of trouble to simply get the gauge lights to track with the dash lights, so maybe it's just for the purist. The practical approach is to just wire the red and orange wires as directed in the instructions, adjust the dash lights until they match the gauges, and leave it at that.

Tom S

[marshallinstruments]

Steve (SRTech) has Marshall dimmer switches that are specifically designed to work with the Marshall MINI OEM look gauges for anyone that would like to dim the gauges. Most people that use the dimmer just set it to the desired brightness then forget about it, but it can be mounted for easy adjustment on the fly. 1 dimmer can be used for multiple gauges.

If you want the gauges to dim along with the OEM gauges Ray (RJB) has created an "inline dimmer" to do this.

[Thomas S]

Originally Posted by marshallinstruments

If you want the gauges to dim along with the OEM gauges Ray (RJB) has created an "inline dimmer" to do this.

I'm interested in this. Why reinvent the wheel? The only questions I have are, will the "inline dimmer" work with both stepper and mechanical gauges (I have both), and is one module sufficient to drive multiple gauges?

Tom S

[SRTech]

Originally Posted by Thomas S

I'm interested in this. Why reinvent the wheel? The only questions I have are, will the "inline dimmer" work with both stepper and mechanical gauges (I have both), and is one module sufficient to drive multiple gauges?

Tom S

One dimmer will do up to 7 gauges. I haven't tried it on a combination. I have them for $25.

Steve

[rjb]

Originally Posted by Thomas S

I'm interested in this. Why reinvent the wheel? The only questions I have are, will the "inline dimmer" work with both stepper and mechanical gauges (I have both), and is one module sufficient to drive multiple gauges?

Tom S

Mine (the in-line) should be able to support at least 4 (I'm guessing more like 7) gauges, I'm currently in the process of getting quotes for the PCB board. I'm probably a month away (maybe sooner) from having them commercially available. I don't believe it will work with the non stepper motor gauges as they dim via the "lighting" wire and not by varying the VCC voltage, Paul at Marshall can confirm. Mine also has a circuit that will turn the lighting on when the dimmer is turned on, this saves the trouble of needing to find a hot wire for the lights. I should have priceing in a couple of days when I get the PCB board qoute and a prototype in hand.

[Thomas S]

Originally Posted by SRTech

One dimmer will do up to 7 gauges. I haven't tried it on a combination. I have them for $25.

Steve

Great! How do I get one?

Tom S

[SRTech]

Originally Posted by Thomas S

Great! How do I get one?

Tom S

Call me.

Steve Tech
Custom Mini Shop
559.320.0004

[marshallinstruments]

RJB's inline dimmer will work with all the Marshall gauges: non-stepper, stepper, and mechanical boost. You hook them up all the same way, i.e. the red output wire from his inline dimmer connects to the 12V ACC gauge connection.

The Marshall dimmer works similarly except it has a separate control knob for brightness, it does not work inline with the OEM dimmer.

[Rowdy]

Got the brackets, pods and psiclone adapter for the mech boost gauge from steve (Fantastic packing job btw). Its all installed and looks beautiful but I havent yet wired the lighting up. Is going via the cigarette lighter for 12V and Ground with the DSC for the amber lighting the best route? I'll post some pics up PDQ!!

cheers

[Tron Chief]

Originally Posted by Rowdy

Got the brackets, pods and psiclone adapter for the mech boost gauge from steve (Fantastic packing job btw). Its all installed and looks beautiful but I havent yet wired the lighting up. Is going via the cigarette lighter for 12V and Ground with the DSC for the amber lighting the best route? I'll post some pics up PDQ!!

cheers

That wiring plan is the easiest way.

[SRTech]

One of my customers has reported back about the vibrating needle problem and how he fixed it. All it took was about an inch of cotton from a cotton ball stuffed into the tube as it gets to the gauge. Thanks, Brian!

Steve

[Rowdy]

I too started up with the vibrating needle. Simple simple fix. go snag an inline restrictor and splice it into the line. Problem solved. Most auto supply shops should have them.

[ranczar]

Can anyone say with any certainty if RJB's inline dimmer circuit will work in an '06 R52, with a Marshall stepper Vac/Boost gauge? If there's a post in this thread addressing this combination, I've missed it. Thanks in advance.

[Tron Chief]

Cotton inserted in vac line I will finally have no more chatter These gauges are so AWESOME

[rjb]

Originally Posted by ranczar

Can anyone say with any certainty if RJB's inline dimmer circuit will work in an '06 R52, with a Marshall stepper Vac/Boost gauge? If there's a post in this thread addressing this combination, I've missed it. Thanks in advance.

I haven't tried it directly on a R52 but I'd be certain that it would. Paul at Marshall bench tested it on his bench setup and it worked fine. I've been using mine now for over a week in my R56 fine.

My only concern WAS is whether or not the R52 used PWM (Pulse Width Modulation), I verified the R56 does, to dim the lights, but I designed it to work either way, so I can't see it being an issue.

I'm waiting on final assembly pricing from my supplier (I should have it Monday) then I can give everyone pricing (I figure retail around $45) with a group buy (discount will depend on final pricing from my supplier).

BTW Not sure if you read my posts above but it also has the convenience of not needing to find a hot wire for the lighting (you can take the amber [or white] LED lighting wire to the dimmer to "trigger" the gauge lighting)

Update: I will work with Steve at SRTech to coordinate the group buy