Neato '79 Gauge Discovery and a few questions?

[joeyg1973]

Sooo.. I found out some neat things about my '79 gauge cluster while I was messing around with it.

1. The speedometer has a pulse generator(vss) attached to it which is four pulses per revolution.
2. On the speedo gauge face, it say that 1062 rpms = 60 mph. Which is about 17.7 rpms = 1 mph.

What does this mean? Well with a simple and cheap item like BASIC Stamp2 http://www.parallax.com it is very easy to change the pulse out to whatever you want which means that you GM computer guys could just skip out on buying a VSS and a new gauge cluster and continue to use your existing stock Toyota one. I don't know how many pulses a GM VSS puts out but it isn't exactly rocket science to read in the the 4 pulses to the BS2 and through about 10 lines of extremely easy to write code, have the chip put out whatever pulse per mile you want. Just takes a little bit of linear algebra. This actually works out great for me too as I am using the variable power steering computer and electric pump from a early to mid 90's MR2.

Now I have a few questions. Since none of the lower 4 gauges have any numbers on them I was hoping someone could tell me what the marks on the guages for the oil preassure and the water temperature numerically line up to? I know that I am sharing a GM water temperature sensor with my MegaSquirt2 and may need to share it with the oil sensor so I need know what those marks represent.

On another note, I am going to replace the fairly useless ammeter with a voltmeter... just need to find a decent guage that has a sweep close to it and make a new backplate. I am also planning on putting in an rpm guage, although I haven't quite figured out just where yet... perhaps on the right side of the speed. I could use some help on finding a voltmeter and rpm guage that would match the sweep range I am looking for. Any thoughts on yet another crazy idea of mine?

 

[motoloco]

I want your old amp guage, my needle went MIA in my 79'.

 

[KY Longhunter]

Stock 40 Tachometer

A Couple of weeks ago there was a thread of a guy trying to mate a OEM Tachometer from a BJ42LX into his FJ40.

https://forum.ih8mud.com/40-55-series-tech/227658-building-factory-tachometer-fj40.html

Dont know if he ever got it to work, but after I read his thread I found that SOR has used FJ40 Tachometer's for $60.


Specter Off-Road-Land Cruiser Parts - Search On-172-81

I thought this would look very cool if it worked.

 

[TOBASH]

On another note, I am going to replace the fairly useless ammeter with a voltmeter... just need to find a decent guage that has a sweep close to it and make a new backplate.

Please let us know what voltmeter and part number and supply house you find. (I then will have to pray that they also make 24 Volt units, as my BJ-44 is a 2 battery unit.)

Best,

T

 

[joeyg1973]

Please let us know what voltmeter and part number and supply house you find. (I then will have to pray that they also make 24 Volt units, as my BJ-44 is a 2 battery unit.)

Best,

T

Voltmeter Gauge. Black Dial, Electric Short-Sweep Voltmeter


Just came across this... it's a 12 volt, not sure they make a 24 volt.

 

[Fast Eddy]

If you're so handy with the microprocessor, why not get a little LCD and use it for both the tach and the voltmeter? I'm sure you can get a stamp-type board with an A->D converter and a voltage divider circuit is pretty easy, even for a software guy like me.

 

[Flash1034]

How and where does a stock Toyota FJ40 tach mount? Will it work on a 78 FJ40?

Thanks,

Flash

 

[Teebag]

Flash in RHD BJ42's it goes like this...

Never heard or seen one from the factory in an FJ or in a LHD

 

[joeyg1973]

If you're so handy with the microprocessor, why not get a little LCD and use it for both the tach and the voltmeter? I'm sure you can get a stamp-type board with an A->D converter and a voltage divider circuit is pretty easy, even for a software guy like me.

Actually I am thinking about going all glass at some point using one of Parallax's Propeller chip and 2-3 of these OLED displays. ?OLED-96-PROP

There are larger versions of those too.

The reason I am not going with a little lcd is that it won't match the existing look of the guage package.

The reason I am not going with all glass at this point is because:

1) I am a Unix Sys. Admin. by trade and I really am not that handy with a microprocessor as I am still learning it. Even though the parallax stuff is made to handle all levels from the very beginner like me all the way up to production engineer types. I am at the very beginner stage.

2) Being a Unix Sys. Admin. ( although I have spent stints doing software development in C, PHP, Python, Jython, etc. ) I don't know that much about designing graphics from scratch and making them asthetically pleasing.

3) I am still learning electronics in general. I don't find it to be too hard anymore, just time consuming to figure it all out at times.

4) I still have plenty of other projects to work on in front of the all glass guage package. MS2Extra with 3fe dist for timing and a ford 6 wasted spark driven right from the MS2Extra, mr2 variable power steering and electric steering pump, the never ending process of cleaning, de-rusing, and painting, rewiring the whole truck, etc, ad nausium, ad infinim

It is too large a project for me to take on by myself, however, if I got some help from some others, I would be willing to put my time in to creating an Open Source all glass automotive packag. I would really need help on the graphics/esthectics part there. Hint Hint Fast Eddy.

 

[Coolerman]

This gauge is a bit unusual, simply indicates if voltage is correct or not, you define the limits. Red if below or above set voltage, and green if normal.
0-30V range so will work for you 24V guys...

Lascar Electronics - EM20-FPSI 1010 - Allied Electronics

 

[John Smith]

Sooo.. I found out some neat things about my '79 gauge cluster while I was messing around with it.

1. The speedometer has a pulse generator(vss) attached to it which is four pulses per revolution.
2. On the speedo gauge face, it say that 1062 rpms = 60 mph. Which is about 17.7 rpms = 1 mph.

What does this mean? Well with a simple and cheap item like BASIC Stamp2 http://www.parallax.com it is very easy to change the pulse out to whatever you want which means that you GM computer guys could just skip out on buying a VSS and a new gauge cluster and continue to use your existing stock Toyota one. I don't know how many pulses a GM VSS puts out but it isn't exactly rocket science to read in the the 4 pulses to the BS2 and through about 10 lines of extremely easy to write code, have the chip put out whatever pulse per mile you want. Just takes a little bit of linear algebra. This actually works out great for me too as I am using the variable power steering computer and electric pump from a early to mid 90's MR2.

Now I have a few questions. Since none of the lower 4 gauges have any numbers on them I was hoping someone could tell me what the marks on the guages for the oil preassure and the water temperature numerically line up to? I know that I am sharing a GM water temperature sensor with my MegaSquirt2 and may need to share it with the oil sensor so I need know what those marks represent.

On another note, I am going to replace the fairly useless ammeter with a voltmeter... just need to find a decent guage that has a sweep close to it and make a new backplate. I am also planning on putting in an rpm guage, although I haven't quite figured out just where yet... perhaps on the right side of the speed. I could use some help on finding a voltmeter and rpm guage that would match the sweep range I am looking for. Any thoughts on yet another crazy idea of mine?

It has been 10 years since I pulled apart my 79 speedo but I don't remember seeing any pulse generator attached to it. Do you have a picture of this thing? Pre 79 speedos also have the 1062 = 60 thing also on the face at the bottom.

 

[joeyg1973]

It has been 10 years since I pulled apart my 79 speedo but I don't remember seeing any pulse generator attached to it. Do you have a picture of this thing? Pre 79 speedos also have the 1062 = 60 thing also on the face at the bottom.

Attach a multimeter that will show you connectivity to the 2 prongs, then spin the flywheel. The multimeter will beep four times per revolution.

 

[FJ40Jim]

It has been 10 years since I pulled apart my 79 speedo but I don't remember seeing any pulse generator attached to it. Do you have a picture of this thing?

FWIW, All ~72ish & newer USA Cruisers have the speed sensor in the speedo head. 69-71 emissions equipped trucks have the speed marker inserted in the speedo cable.

 

[John Smith]

Attach a multimeter that will show you connectivity to the 2 prongs, then spin the flywheel. The multimeter will beep four times per revolution.

Thanks for the excellent picture. I did not dismantle the odometer assembly but always wondered what it looks like in there.

Your question about what the hash marks represent is going to be different for most every truck. The stock gauges are not very accurate to begin with.

 

[amaurer]

Actually I am thinking about going all glass at some point using one of Parallax's Propeller chip and 2-3 of these OLED displays. ?OLED-96-PROP

There are larger versions of those too.

The reason I am not going with a little lcd is that it won't match the existing look of the guage package.

The reason I am not going with all glass at this point is because:

1) I am a Unix Sys. Admin. by trade and I really am not that handy with a microprocessor as I am still learning it. Even though the parallax stuff is made to handle all levels from the very beginner like me all the way up to production engineer types. I am at the very beginner stage.
...
3) I am still learning electronics in general. I don't find it to be too hard anymore, just time consuming to figure it all out at times.
...
It is too large a project for me to take on by myself, however, if I got some help from some others, I would be willing to put my time in to creating an Open Source all glass automotive packag. I would really need help on the graphics/esthectics part there. Hint Hint Fast Eddy.

I can help with the electronics and firmware. I've actually built a few uC-based tachometers before for one-off lab equipment. While they only used 4digit LED segment displays my asm-fu is strong, I'm sure I can handle anything.

With respect to your first project, a PIC-based pluse train converter for GM swaps would cost about $10 in parts and I could have it running in an evening if people actually wanted that sort of thing. As you noted the Parallax stamps are neat for beginners, but they're VERY expensive compared to the $3 PIC that is the heart of every stamp - might as well use them directly.

 

[BinaryDude]

I have actually been thinking about building something similar to track performance data, and for the future WVO project i have planned...

Last time i programmed, I used a Rabbit2k board with a web interface... </geek>

But i would be glad to help... when i have my Troopy to test on...

 

[joeyg1973]

Eish assembly... eish... I tend to head for the easier to code stuff... hence why I like the parallax stuff. I have never even seen assembly code in my life. I try to avoid C too nowadays as there are much easier to use languages like python or jython. Perl I avoid like the pague because I write scripts in it and come back a month later and have no clue what I wrote.

The reason why I want to go parallax is because it has low entry point and that means it is easier to get help on the project. When we need to get down to assembly... well that would be the speciality of folk like you... not me. Plus that proppeller chip is one sweet device and gives us a huge head start.

 

[Ming89FJ62]

My two pigs both have the pulse generators as part of the Cal emissions circuit. FWIW.

 

[amaurer]

Eish assembly... eish... I tend to head for the easier to code stuff... hence why I like the parallax stuff. I have never even seen assembly code in my life. I try to avoid C too nowadays as there are much easier to use languages like python or jython. Perl I avoid like the pague because I write scripts in it and come back a month later and have no clue what I wrote.

The reason why I want to go parallax is because it has low entry point and that means it is easier to get help on the project. When we need to get down to assembly... well that would be the speciality of folk like you... not me. Plus that proppeller chip is one sweet device and gives us a huge head start.

I agree the propeller is nice, thats actually an awesome device, I might grab a few for future projects.

The problem is, for a tach or other timing-critical device your accuracy is determined by how well you know your instruction timing. When you write in a higher level language you usually won't know just how many instructions it takes to execute a line of code - best case is only one but you could actually wind up with 4 or many more instructions on a line. Python is actually pretty bad in this respect, as many of the functions are sorta like C macros... layers and layers of hidden instructions.

Example:
C:

i++;

You don't know if you compiler is going to translate that to:

incf i;

or in a worst case something like:

movfw i;
addlw 0x01;
movwf i;

On a computer you might have a background timer to keep things in sync, but on an embedded device you don't.

Its funny this came up, I have a bunch of ideas I'd like to try for my BJ42... combining hobbies, I guess. For one I want to rig up a new glow controller that lights up when a certain plug temperature is reached (rather than the simple coil used now). I've also been thinking about a cruise control........

 

[Fast Eddy]

the Parallax stamps are neat for beginners, but they're VERY expensive compared to the $3 PIC that is the heart of every stamp - might as well use them directly.

My biggest uC project was for a mountain bike. I built a combination speedo and halogen headlight controller. It would auto-dim the light based on bike speed for increased battery life. I used a bare PIC with a little serial BIOS so you could self-load code over a serial cable. The program was written in object-oriented assembly.

The display was an i2c lcd; nothing fancy.

I do have a background in graphics with some UI experience.

My current company makes a $15 micro that can encode and decode video. It can drive an HD display directly. You could watch TV on your all-glass cockpit and encode a couple of rock cameras to disk at the same time, then upload the videos over WiFi when you got home. It runs Linux 2.6.23.