86’ 6.9 tachometer rewire

[Laine D]

Ever since I bought my truck the tach has never worked. I finally got around to checking the wiring and discovered that everything was good. Took the guage cluster out and took it apart. I took the tachometer gauge face off and found something that somewhat reminded me of a copper magneto. Looking at it closer I realized that 3 of the copper wires that are supposed to be attached to these little posts had come off. Doing my mess to jump the wires with some copper I got the tach to work. Now I’m wondering if anybody has ever taken this copper ***** type thing out and re soldered everything to make the tach work again. Or if anybody has even had any experience with the tach internals. Kicking myself fir not getting any pictures :/
The internals are actually pretty interesting and I’d like to learn more about how it works if anybody has any knowledge on it

 

[BeastMaster]

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My tach only has three wires...key on power (+), ground (-), and tach sensor ( S, returned to ground. )

3.226 Khz = 4000 RPM on mine... It may be wrong, as calculated to be 3.533 Khz.

You must be registered for see images attach

Signal generator is old Android phone loaded with

https://f-droid.org/en/packages/org.billthefarmer.siggen/

And patch wire made from 3.5 mm earbud wire.

 

[Selahdoor]

I came in here just to see the 86 feet of tachometer rewiring.

I was disappointed.

 

[Laine D]

I came in here just to see the 86 feet of tachometer rewiring.

I was disappointed.

Hahahaha I didn’t realize it looked like that

 

[BeastMaster]

Did you want the photo of four alligator clips on the pins?

I am designing some Arduino stuff for my van...and this thread caught me while tinkering with the gauge cluster circuits.

What I'm after is something to measure glow plug current, monitor temperatures, and make intelligent glow plug control knowing block temperature. And control a couple of

https://www.amazon.com/gp/aw/d/B00DE3HY4K

To completely shut down van and trailer power.

Actually, the tach circuit is quite simple and testable using a cellphone loaded with a signal generator app to mimic the VR sensor. Works for the VSS sensor too.

 

[ifrythings]

Did you want the photo of four alligator clips on the pins?

I am designing some Arduino stuff for my van...and this thread caught me while tinkering with the gauge cluster circuits.

What I'm after is something to measure glow plug current, monitor temperatures, and make intelligent glow plug control knowing block temperature. And control a couple of

https://www.amazon.com/gp/aw/d/B00DE3HY4K

To completely shut down van and trailer power.

Actually, the tach circuit is quite simple and testable using a cellphone loaded with a signal generator app to mimic the VR sensor. Works for the VSS sensor too.

@BeastMaster if you need a hand at all I got most of my project done, will be transplanting this to two 7” screens soon to display everything I’m monitoring.

You must be registered for see images attach

 

[BeastMaster]

if you need a hand at all I got most of my project done, will be transplanting this to two 7” screens soon to display everything I’m monitoring.

Very interesting!

Nextion HMI displays?

For now, I am doing thermocouples - up to sixteen of em - and magnetic cores - where I have them in a resonant oscillator, and am looking for the permeability shift when I ram amperes of DC current through the center of the core.

Intent is to measure glow plug currents and battery currents. What I have isn't all that linear, but it oughta be reliable. Otherwise, hall effect.

And some stray housekeeping. Timing glow plugs, managing hotel load, maybe some rudimentary security.

For now, a 20x4 LCD, later I2C slave. Maybe later a Bluetooth RS232 and write a companion app for my tablet. But that's way off. Considered, but not now

I am a bit mechanically challenged about replacing my dashboard to implement the new displays.

I make heavy use of I2C and multiplexers to avoid running out of I/O. Also to make troubleshooting easier and easy to bypass should I have it fail. As long as I can fall back to raw IDI by clipping two terminals together.

You know, I must spend 1000 hours at the EAGLE terminal fo every hour of soldering iron time. I still run EAGLE4.

I wish I lived closer to you... You are quite ahead of me...and looks like you have your ducks in a row.

 

[Laine D]

@BeastMaster if you need a hand at all I got most of my project done, will be transplanting this to two 7” screens soon to display everything I’m monitoring.

You must be registered for see images attach

That is extremely cool!

 

[Laine D]

Did you want the photo of four alligator clips on the pins?

I am designing some Arduino stuff for my van...and this thread caught me while tinkering with the gauge cluster circuits.

What I'm after is something to measure glow plug current, monitor temperatures, and make intelligent glow plug control knowing block temperature. And control a couple of

https://www.amazon.com/gp/aw/d/B00DE3HY4K

To completely shut down van and trailer power.

Actually, the tach circuit is quite simple and testable using a cellphone loaded with a signal generator app to mimic the VR sensor. Works for the VSS sensor too.

I’m trying to fix mine. Where the copper wire is connected to the 3 prongs, 1 or maybe 2 of the wires aren’t even connected. I jumped the 2 prongs on the top with a screwdriver and the tach started working. Not sure why

 

[BeastMaster]

I believe the motor/pointer of our tachs is of an air core moving magnet design, likely driven with a custom IC.

Here's a generic driver IC:

PDF LM1819 Air-Core Meter Driver - Digi-Key

https://media.digikey.com/pdf/Data Sheets/National Semiconductor PDFs/LM1819.pdf

The mechanics of this meter design makes it possible to have a true 360 degree display. With nothing winding up to restrict things.

 

[ifrythings]

Very interesting!

Nextion HMI displays?

For now, I am doing thermocouples - up to sixteen of em - and magnetic cores - where I have them in a resonant oscillator, and am looking for the permeability shift when I ram amperes of DC current through the center of the core.

Intent is to measure glow plug currents and battery currents. What I have isn't all that linear, but it oughta be reliable. Otherwise, hall effect.

And some stray housekeeping. Timing glow plugs, managing hotel load, maybe some rudimentary security.

For now, a 20x4 LCD, later I2C slave. Maybe later a Bluetooth RS232 and write a companion app for my tablet. But that's way off. Considered, but not now

I am a bit mechanically challenged about replacing my dashboard to implement the new displays.

I make heavy use of I2C and multiplexers to avoid running out of I/O. Also to make troubleshooting easier and easy to bypass should I have it fail. As long as I can fall back to raw IDI by clipping two terminals together.

You know, I must spend 1000 hours at the EAGLE terminal fo every hour of soldering iron time. I still run EAGLE4.

I wish I lived closer to you... You are quite ahead of me...and looks like you have your ducks in a row.

sorry to the op for high jacking your thread

Yes I’m using nextion displays, got a great deal on the 7” enhanced version and I’m thinking about buy the 7” intelligent series to have sound and video capabilities.

I found that ford(international) used high temp thermistors for the egt pre egr that go up to 1800F, easy to drive, no special wiring issues and they react very quickly!
For measuring current that seams like a awfully technical way to measure it, I believe temperature is going reck havoc on your measurement. An Acs758 hall ice would be easy to use and it has built in noise suppression, temperature compensation and more, worth looking at.

I’m using a 16 channel multiplexer for the bulk sensor inputs, I was using i2c for my last display but it’s not really meant to go off board like how I was using it, though it did work.

I need to find a good pcb design software, the new eagle is so complex I spent several hours on it and didn’t get anywhere, the older eagle was easier to use.

 

[BeastMaster]

Sounds great!

Thought I was the only one crazy enough to do this.

And I felt the same way about Eagle. It wasn't simple anymore. And I felt the subscription model is fraught with the risk of revision creep. All too often, I need to revisit 20 year old files.

So, I still use my old Eagle 4 and 6 with their perpetual license.

Anyway...I guess I jumped into this thread because I have been doing a personal quest as to what makes my van run, and was pleasantly surprised how simple the tach circuit turned out to be, and how easy it was to repurpose an Android phone to generate the VR signals.

And a big hat tip to Bill the Farmer for putting up his signal generator app on the open source Android forum, F-Droid.org .

Bill has a couple more quite useful apps there as well... An oscilloscope, spectrum analyzer, and musical tuner. The oscilloscope has limitations imposed by phone hardware, but, with appropriate attenuators, quite useful. Phone sees it as a plug in mic on the earbud connector.