Possible gauge protection solution

analogdesigner · Feb 22, 2015

Everyone,

If you are interested in ordering one of these, you may do so by sending $37.00 plus $8.00 (shipping and handling) totaling $45.00 by check or PayPal. If you order multiple units, please only pay for shipping and handling once! I will be placing another order for parts this coming week and I will process your order ASAP. I want to thank all of my prior customers for their positive comments on the build quality and ease of installation.

Also, I am looking into a designing an isolated +12 volt power supply for supplying clean, controlled, precision power to the gauges. First, let's see how things work with this current scheme. Thanks all, Jay. www.analogdesign.com

By check, $45.00 to:

Jay Philippbar
2006 Via Solona
San Clemente, CA 92673
(949) 412-8889
gtsaver@cox.net

OR

By PayPal, $45.00 to:

gtsaver@cox.net
PLEASE MAKE SURE YOUR MAILING ADDRESS IS INCLUDED!

My personal website:
www.analogdesign.com

UPDATED on 4-21-2015: I have found a special "grounding washer" that fits perfectly to solve the problem that jcthorne has identified. The washer is designed to penetrate the paint on the panel to ensure a good ground connection. Please see the images below. I will be doing additional updating on this within the next few hours. I am going to be mailing out two washers with instructions to everyone by the end of the week (as soon as the parts arrive). Jay

Hello everyone,

Sorry for being gone for so long as 2014 was my year from hell.

During my time off last year I have decided to design a device that may provide some additional protection to our gauges. First of all I have always had the belief that most of the gauge failures are due to a voltage transient on the car's electrical system. This could be a very short duration high voltage spike or even a reverse voltage spike. I had built a simple device that clamps any unwanted voltage transients regardless of the polarity. This is simply a special selected diode that clamps any voltage transient that exceeds 15.5 volts as well as any negative voltage greater than about -0.8 volts. The basic assembly is shown in the first image. The fuse adapter on the left is a Littlefuse “Add-a-Fuse” which plugs into the fuse block where the fuse for the gauge cluster originally was. The original fuse for gauge cluster is now plugged into this adapter. The second fuse is for the protection diode; in case it shorts (if it shorts then it WAS protecting the electrical system!). The second image shows it installed into the fuse block in my car (note the yellow arrows). Note: my fuse block looks very busy because I also have a wideband O[SUB]2[/SUB] sensor.

I am not going to make any claims that this will prevent gauge damage! I had my oscilloscope setup in my car and monitored the voltage going to the gauge cluster. I was able to see voltage transients approaching 15.5 volts (they were narrow as expected) and with the protection diode it clamped everything to 15.2 volts! I deliberately selected the protection diode to operate very close to the vehicle’s maximum system voltage. With the engine running I cycled through all of the accessories in the car, A/C, headlights, fans, etc. in order to try and make the electrical system as “noisy” as possible. I have been using this for about four months without any problems.

If anyone is interested I can make a simple parts list and/or even build some.

Thanks all,

Jay

mopar · Feb 22, 2015

cant hurt anything to help save the gauges is great very nice

PL510*Jeff · Feb 22, 2015

old school still works.

bonehead · Feb 22, 2015

I'm certainly willing to try it. Just for clarification, this is in the junction box in the passenger footwell?

As for the voltage spikes, I know it has been mentioned before, but I'm fairly certain that one of the causes is not allowing the gauges/odometer to cycle before starting the ignition. I'm 99% sure that's how l lost my oil gauge. Turn the key to the second position, WAIT for the gauges to cycle and the odometer to display numbers, THEN push the start button.

jcthorne · Feb 22, 2015

If you would be willing to build a few, I would certainly be interested in installing one. Looks like good protection for possible failure mode to me. Just looking at the one in the photo, your electrical assembly skills are much better than mine. Look forward to hearing from you.

FBA · Feb 22, 2015

It looks like a simple IN4XXX clamp diode in series with the 12 volt line...is that what you're using? What's the current rating of that guy? Is that the only place the gauges power off in the car?

Wwabbit · Feb 22, 2015

Interesting. Yes, please post the diode value or source, I'd like to whip one up.

33Bravo · Feb 22, 2015

I would certainly be willing to buy one and test it out!

Spring driving weather is still a bit away though here in Minneapolis

Thanks for doing this!!

CJ428 · Feb 22, 2015

That's a nice idea. I would like to try it.

texas mongrel · Feb 22, 2015

I suspect that the cause is not high voltage spikes but low input voltage failing to initialize the gauges. If I haven't driven my car for a while, when I get in, random gauges don't work. Drive for a while and the next time I crank 'er up, everything is fine. This has happened over a dozen times during my ownership, and (touch wood) as soon as the battery gets a charge everything works.

analogdesigner · Feb 22, 2015

bonehead,

Yes, I forgot to mention this and you are correct that the fuse block IS located in the passenger foot well.

I wish that I could get my hands on a few of these blown gauges so that I can examine the internal circuit board.

Jay

bonehead said:
I'm certainly willing to try it. Just for clarification, this is in the junction box in the passenger footwell?

As for the voltage spikes, I know it has been mentioned before, but I'm fairly certain that one of the causes is not allowing the gauges/odometer to cycle before starting the ignition. I'm 99% sure that's how l lost my oil gauge. Turn the key to the second position, WAIT for the gauges to cycle and the odometer to display numbers, THEN push the start button.

analogdesigner · Feb 22, 2015

jc, I may consider building a small run of maybe 10 to 20 units. Later in this post I will have a parts list for the DIY persons. More later, Jay

jcthorne said:
If you would be willing to build a few, I would certainly be interested in installing one. Looks like good protection for possible failure mode to me. Just looking at the one in the photo, your electrical assembly skills are much better than mine. Look forward to hearing from you.

analogdesigner · Feb 22, 2015

FBA,

The protection diode is a "Transient Voltage Suppressor" (TVS). This particular device is rated for 240 amps and/or 5,000 watts peak clamping capability. The device that I selected will clamp very close to our car's normal operating voltage, in other words I want to stomp on any voltage transients good and hard. This device can also switch on in picoseconds! A 1N400x diode would not do anything, please do not try that.

Here is the parts list:

1. Littelfuse FHM200BP ATO Add-A-Circuit Kit

2. Littelfuse 5KP13A

The total parts cost should be under $30 including shipping cost. Item #1 can be purchased online, try Amazon. Item #2, try Digi-Key or any other electronic component supplier.

Later I will show you a detailed view of how to install the diode and then how to properly install it into your fuse block. Also these Add-A-Circuit fuse adapters must be installed in the correct direction! More on that later as I must get back to work in the lab. :thumbsup

Jay

FBA said:
It looks like a simple IN4XXX clamp diode in series with the 12 volt line...is that what you're using? What's the current rating of that guy? Is that the only place the gauges power off in the car?

analogdesigner · Feb 22, 2015

texas,

Yes, I agree with your observations. I must get technical for a moment in order to explain why there could be other things going on inside these gauges.

Without knowing what's inside of these gauges, I would think that they have a simple microcontroller, which is a programmable integrated circuit. These microcontrollers operate on low voltages, 3.3 or 5 volts. If so, there is a voltage regulator inside the gauge that may get saturated when the car's battery gets low. When the car suddenly starts, the alternator suddenly kicks the voltage up to around 14 volts. So it's possible that this voltage regulator within the gauge cannot respond quickly enough, therefore it may not be capable of regulating the 3.3 or 5 volts for the internal circuitry. I have seen things as this when too many cost cutting measures are put into play. Do any of you old-timers remember the Muntz TV?

Jay

texas mongrel said:
I suspect that the cause is not high voltage spikes but low input voltage failing to initialize the gauges. If I haven't driven my car for a while, when I get in, random gauges don't work. Drive for a while and the next time I crank 'er up, everything is fine. This has happened over a dozen times during my ownership, and (touch wood) as soon as the battery gets a charge everything works.

analogdesigner · Feb 22, 2015

Here is a schematic of this simple gauge protection device:

MJSFRX · Feb 22, 2015

jcthorne said:
If you would be willing to build a few, I would certainly be interested in installing one. Looks like good protection for possible failure mode to me. Just looking at the one in the photo, your electrical assembly skills are much better than mine. Look forward to hearing from you.

Jay, count me in on a group build buy if that's an option. Thanks Marc

analogdesigner · Feb 22, 2015

Marc, okay, thanks! Jay

MJSFRX said:
Jay, count me in on a group build buy if that's an option. Thanks Marc

cobra498 · Feb 22, 2015

analogdesigner said:
texas,

Yes, I agree with your observations. I must get technical for a moment in order to explain why there could be other things going on inside these gauges.

Without knowing what's inside of these gauges, I would think that they have a simple microcontroller, which is a programmable integrated circuit. These microcontrollers operate on low voltages, 3.3 or 5 volts. If so, there is a voltage regulator inside the gauge that may get saturated when the car's battery gets low. When the car suddenly starts, the alternator suddenly kicks the voltage up to around 14 volts. So it's possible that this voltage regulator within the gauge cannot respond quickly enough, therefore it may not be capable of regulating the 3.3 or 5 volts for the internal circuitry. I have seen things as this when too many cost cutting measures are put into play. Do any of you old-timers remember the Muntz TV?

Jay

The microprocessor drives the gauge air motor coils directly with no protection on the leads for emf generated by the coils. I only checked two gauges but the micro was no longer clocking in either defective gauge. Not saying it isn't power supply related, but could be they should have used a buffer circuit for the air motor coils.

shesgotlegs · Feb 22, 2015

Me too please if you decide to proceed .

shesgotlegs · Feb 22, 2015

Thanks!

Possible gauge protection solution

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