Instrument cluster voltage regulator upgrade

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Tatsadasayago
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Instrument cluster voltage regulator upgrade

Post by Tatsadasayago »

Having suffered the failure of my stock gauges recently, I've been looking into getting rid of the 'voltage pulser' inside my temp gauge.
I located a suitable integrated circuit regulator that steps 12VDC down to 6VDC (NTE962, $1.59 from frys.com) and have a donor gauge to test this on.
Image
So,
The I post on the back side of the gauge is where 12VDC arrives from switched ignition.
The A post is where the 'pulser' has 5-6VDC and it feeds the gauge strip as well as the other two gauges.
The S post connects to the sending unit which goes through it's variable resistor to ground completing the circuit.
Image
Above is the NTE962 in a TO220 housing.
I would like to mount it inside the gauge housing but it's a bit cramped so I am looking for advice on where to mount it and suggestions on how to insert it into the circuit while disabling the 'pulser'.

Ideas?

Jim
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A collection of parts flying in close formation

serehill
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Re: Instrument cluster voltage regulator upgrade

Post by serehill »

http://forums.ifsja.org/showthread.php? ... 9&t=120103


I prefer the 7806 but the specs are close enough to work. the VR doesn't have to be internal
Last edited by serehill on Thu Apr 30, 2015 2:22 pm, edited 1 time in total.
1980 Honcho 258 4 speed mostly stock with 4 " lift.

WIP

You know the rude dude from IFSJA


1980 Cherokee wrangled & mangled
MSD complete system
Eddy intake
Holley 650
Comp cam 270H
4" Rusty's
Ramsey 12K winch
208
Built to drive not sit in the garage.


No longer strangled. I didn't build it for anyone else.
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Re: Instrument cluster voltage regulator upgrade

Post by Tatsadasayago »

Thanks for the link serehill. I did a search, but didn't find that thread.

Going to place the VR on the back side of the PCB and add a capacitor to keep RFI/EMI down for the HF radio insall later.

Thanks Sir!
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carnuck
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Re: Instrument cluster voltage regulator upgrade

Post by carnuck »

A lot of classic car sites sell a clip on IVR to "fix" the dead gauge issue. It's actually supposed to be 5 VDC not running but you'll figure out the difference in the gauges in short order.
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Re: Instrument cluster voltage regulator upgrade

Post by Tatsadasayago »

carnuck wrote:A lot of classic car sites sell a clip on IVR to "fix" the dead gauge issue. It's actually supposed to be 5 VDC not running but you'll figure out the difference in the gauges in short order.
I figured 6V would help the toasted windings and leave me with some room to adjust the gauges with those slots. I have aftermarket gauges under the dash for comparison. My biggest concern is having a somewhat accurate fuel gauge. The rest are for amusement purposes of course :)
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letank
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Re: Instrument cluster voltage regulator upgrade

Post by letank »

It is on the second page, and it is stuck to the housing of the speedo, sometimes IFSJA does not connect:

http://forums.ifsja.org/showthread.php?t=120103&page=2

Quote:

If you look close to the side of the speedo housing you can see the LM7806 voltage regulator I installed using the housing for a heat sink. The output pin lays across the "A" trace on the PCB making an easy solder connection. The red wire on pin one is jumpered to the trace connected to pin E of the round connector (KO12V). The gound pin was cut off and it is grounded through the tab to the speedo housing. The "noise filter" was removed to break the 12V connection to the temperature gauge since it is no longer needed. If you look on the far left side you can see a .01uF capacitor from the "A" trace to the ground trace to filter noise. Just a precaution, it probably would not be needed.

Glad to see you got it.
Is that a .01 uf 25vdc cap?

I am assuming a 1 watt 1k ohm resistor?

that 7806 is pretty standard reg & the cap is highly recommended that VR is pretty noisey.

Is this correct? there should be a cap on input & output.

I took some screenshots and can add later.

Adding screenshot from the IFSJA site

Image

Image

Image
Last edited by letank on Fri Sep 18, 2015 2:04 pm, edited 2 times in total.
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tgreese
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Re: Instrument cluster voltage regulator upgrade

Post by tgreese »

You don't have to used a fixed voltage device for this application. The 7805 and 7806 reduce the parts count if you want a specific voltage, but the same type of device exists for an adjustable voltage. Look at the LM317 - http://www.ti.com/general/docs/lit/getl ... er=slvs044 - all you need are two or three additional resistors at ca 10c each, to pick any voltage from about 1V less than the supply to zero. Adjust the voltage until you get the performance from the gauges that you want.

You can add capacitors across the input or output for better ripple rejection, but I think you don't need this for this application and since your supply is already filtered DC. Look at the app note for the device that you pick - there may be a capacitor across the input or output required to make the device stable. But if the app note does not show any capacitors in the example circuit, then you don't need any.

Also realize that these devices essentially insert a variable resistance controlled by a feedback circuit to create their target voltage. If your input voltage and load are constant, all you need is a pair of resistors (a voltage divider) to make a reduced voltage. This works fine as long as the load is small compared to the current through the divider. An alternative that is less sensitive to the load would be a zener diode.

Image

Pick your zener voltage to be the voltage you want across the load. http://en.wikipedia.org/wiki/Linear_reg ... _regulator

Realize that Jeep likely used this goofy vibrator thing instead of some kind of voltage divider because of heat. The vibrator is a crude form of pulse width modulation - turn the voltage on and off rapidly so that the average voltage is what you want. This makes a lot less heat than the resistive devices, because the excess voltage across a resistive divider is dissipated as heat.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
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Re: Instrument cluster voltage regulator upgrade

Post by serehill »

The voltage does fluctuate so the 7806 is a good choice keep the caps closest to the VR. Using the Speedo housing for a heat sync in open air rocks.
The device has literally no heat when set up like this. you wouldn't want to contain the device. The capacitors are like .39 cents each cheap insurance to not worry about it.. It's more stable than the factory system by far. The after market bypass systems are 10x more money for exactly the same thing. The entire modification is less than 5 bucks in parts.
Last edited by serehill on Thu Apr 30, 2015 6:58 pm, edited 1 time in total.
1980 Honcho 258 4 speed mostly stock with 4 " lift.

WIP

You know the rude dude from IFSJA


1980 Cherokee wrangled & mangled
MSD complete system
Eddy intake
Holley 650
Comp cam 270H
4" Rusty's
Ramsey 12K winch
208
Built to drive not sit in the garage.


No longer strangled. I didn't build it for anyone else.
If you can't improve it why waste your time?
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Tatsadasayago
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Re: Instrument cluster voltage regulator upgrade

Post by Tatsadasayago »

Thanks for sharing the link and images. I would have done the mod much differently had I not seen 710s slick setup.
Makes more sense and yes, heat shouldn't be an issue with the speedo housing as a sink.
I'll pick up a few 1uF 25V caps today and see about getting this done tomorrow.

Thanks guys for your help!

Jim
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tgreese
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Re: Instrument cluster voltage regulator upgrade

Post by tgreese »

Here's your 7806 data sheet - https://www.fairchildsemi.com/datasheets/LM/LM7806.pdf

Note that, if it has a metal tab, that it connects to ground. Make sure that whatever surface you mount it to is also at ground potential, or can be connected to ground.

Look at figure 9. That's your ideal configuration. As Serehill mentions, the caps are cheap parts. Use generic capacitors with plastic dielectrc (mylar typically) of voltage rating better than the peak voltage you ever expect to see. You can order the parts through Digikey or Mouser and the shipping will be three times the cost of the parts. Cheaper will be an electronics store near you or a friendly local electronics hobbyist. If you want to buy through Mouser or Digikey, let me know and I can tell you the PNs to buy.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.
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Re: Instrument cluster voltage regulator upgrade

Post by Tatsadasayago »

Oh, the NTE962 I grabbed is a 7806UC equivalent. Will this be a problem in this case?
Last edited by Tatsadasayago on Thu Apr 30, 2015 3:11 pm, edited 2 times in total.
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tgreese
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Re: Instrument cluster voltage regulator upgrade

Post by tgreese »

Nope. Generic equivalents.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
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Re: Instrument cluster voltage regulator upgrade

Post by Tatsadasayago »

I just looked at figure 9 as you suggested Tim, and it shows a .33uF cap (C1) on the input side and a .1uF on the output (C0). Is this difference in caps that forces the IC to act as a fixed voltage reg?

Disregard, I figured it out after reading the notes below.
C1 is required if the regulator is located an appreciable distance from the power supply filter. (In this case the battery)
C0 improves stability and transient response.

Thanks!
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Re: Instrument cluster voltage regulator upgrade

Post by tgreese »

No. These 78XXs will always have a fixed output voltage when connected as shown in the note.

The capacitors on the input and output have similar purposes. Ci on the input side smooths the input voltage, protecting the device from any voltage spikes or high-frequency noise from the power supply. Co on the output side helps stabilize the voltage regulator by filtering (frequency limiting) any strong transients in the load. Fairchild chose these values as optimum for this purpose, but I'm sure you all you need to do is get close to that value. So don't sweat it if you can only find, say, a 0.5 and not a 0.33. More capacity or a higher voltage spec won't matter.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
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Re: Instrument cluster voltage regulator upgrade

Post by Tatsadasayago »

Much appreciated Tim! :)
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serehill
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Re: Instrument cluster voltage regulator upgrade

Post by serehill »

Tim as usual is on mark. The input side could get trash from the alternator & amplify it so it is wise to filter both line & load of the transistor to ensure clean input both protect, stabilizes & creates a better source for the load filter to deal with. You can always isolate the tab if that is an issue. It winds up being an advantage though. You can cut the ground pole off if you attach the tab. Not only do you have a large suface ground connection you have an excellent heat sink. Be sure to use either transistor paste or dielectric silicone to keep corrosion at bay. Far better than the stock unit.

if that tranny cross reference to the 7806 then you're golden.
1980 Honcho 258 4 speed mostly stock with 4 " lift.

WIP

You know the rude dude from IFSJA


1980 Cherokee wrangled & mangled
MSD complete system
Eddy intake
Holley 650
Comp cam 270H
4" Rusty's
Ramsey 12K winch
208
Built to drive not sit in the garage.


No longer strangled. I didn't build it for anyone else.
If you can't improve it why waste your time?
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Tatsadasayago
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Re: Instrument cluster voltage regulator upgrade

Post by Tatsadasayago »

I ran over to Fry's and snapped up a few .01uF/100V and .33uF/50V multilayer ceramic caps. I was looking for electrolytic or mylar but nothing even close left on the shelf.
I'll cut the ground pole off and solder the cap leads to the base tab. I am assuming keeping the leads short is as important here as it is in RF circuits and yes, I have some Arctic Silver for the mount point.

Your advice is greatly appreciated!
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tgreese
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Re: Instrument cluster voltage regulator upgrade

Post by tgreese »

Ceramic caps are fine. I'd avoid electrolytics for something like this.

Don't worry about the wiring path. The caps short out any high frequency - that's their purpose.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.
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Tatsadasayago
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Re: Instrument cluster voltage regulator upgrade

Post by Tatsadasayago »

Thanks Tim!
Will pull the cluster in the morning and get after it!
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letank
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Re: Instrument cluster voltage regulator upgrade

Post by letank »

Picts of your soldering artwork.... my CVR just gave up yesterday...
Michel
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85 Gwag (229 Kmiles... the running test lab)
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