Multi-function engine monitor gauge

[thebuildist]

I've had a crazy thought.

The Onan twin-cylinder in my 4020 has a know issue where the valve seats will be damaged if your Cylinder Head Temperature gets too high.

So I made sure to install the gasket around my oil filter, but I also bought a twin-cylinder CHT gauge from Amazon. I haven't installed it yet.
https://www.amazon.com/gp/product/B01G6 ... asin_title

One thing I don't like is that it has a rectangular LCD readout, that's very difficult to read in sunlight. And even though I have an unused 2" round cutout in my dashboard (Currently has an inoperative hour meter) this new rectangular gauge won't fit that cutout.

Then I stumbled across this video, showing how easy it is to create a configurable guage display for an Arduino.
https://www.youtube.com/watch?v=k2c2zCmC_X0

And it hit me: what if I connected those CHT probes to an Arduino and then displayed it on one of these little round displays? Wouldn't that look a lot better?

But wait! There is a LOT more engine/system information that I'd like to be able to monitor:
CHT
RPM
Hydraulic pressure
Hydraulic temp
Engine oil temp
Voltage
Amps

But I don't have room for 7 different gauges. But what if I could monitor all those data points using a single arduino, and display any one of them at a time? Basically you'd have a push-button on/near your gauge, and when you push the button the display would rotate through to show you each of your monitored data types and display a gauge with its current value.

So I did some Googling, and found someone who already did something like this:
https://bitbucket.org/R_P_Ryan/enginemonitor/wiki/Home

His work confirms to me that it can be done, and gives me a starting point to begin coding the Arduino to work with my specific data types.

But there are a couple major shortcomings:
1. He's using the same kind of hard-to-read lcd display that came with my CHT gauge. Wrong shape, poor visibility in daylight.
2. The little round display from the video isn't great either: It's only 1.3" in size, way smaller than our 2" cutout. And it's only SLIGHTLY easier to see than the rectangular LCD display. It's about 300 nits brightness, which is going to be tough to see in daylight. Maybe a deep round shroud to shade it? I haven't ruled it out, but I'm hesitant to try to use that.


So I've done some research into the available types of displays and I think I've come up with what might be a great idea:

I've ordered a $7 tachometer from Amazon.
https://www.amazon.com/gp/product/B08J7P4ZWZ

It'll fit the 2" cutout in my dashboard, and it simply counts the number of 12v pulses it sees per minute. On an Onan you hook it up to the voltage regulator, where there is apparently a single 12v pulse per rotation of the engine.

If all else fails, I'll install this tach in my dash.

BUT: I can actually DRIVE this tachometer FROM the Arduino: I can configure the Arduino to SEND a certain number of voltage pulses per minute to this gauge, and the gauge will move the needle to that value.

So if I were to modifiy the tachometer gauge in a certain way, I could use it as my universal indicator:
1. It needs a configurable green/yellow/red scale to indicate the "OK/NOT OK" range. Every gauge's scale of "OK" range is a little bit different. So we need to have our gauge's "OK" scale to be reconfigurable. This could be done by embedding a series of 6 or 8 RGB led lamps across the top of the gauge face. So at the same time that the Arduino is telling the gauge needle to move to, say, "11 o'clock", it would also light up the various led lamps to show you green, yellow, and red points that will show you the acceptable range for what we're displaying.

2. It needs to display to the user the data's NAME and SCALE: WHAT KIND of data the gauge is displaying, and WHAT NUMBER is meant by the needle's position. For this I'd actually need a second display, a small one that scrolls text across it. For example "Volts -- RED @ 12.5, 16" ("The gauge is reading "Voltage" and the scale is redline (low) at 12.5 volts and redline (high) at 16 volts") The readability of that textual information is not nearly as important. All you really need to be able to see is the data name, because you can tell by the needle position whether the data is in an OK range or not. But if you really want to know, you can patiently/carefully read the full text to see what the scale actually is.

I imagine it looking something like this:

Volts

Oil Temp


I already have two CHT probes and an Arduino. My first plan is to confirm that I can hook them all together and read the temp inside the Arduino.

For that I have to buy $18 worth of "temperature probe driver boards". It comes with 4 boards, so I'd be set up to monitor 2 cylinders, hydro oil and engine oil.
I already have what I think I'll need to monitor RPM.

And I'll tear apart the tach and confirm that it has internal room to fit the embedded RGB LED's.

Assuming those are positive, I'll look at ordering a little scrolling text display (about $20) and the parts I need to monitor voltage and current. (about $15)
I haven't yet researched my options for a high pressure transducer to show hydraulic pressure. Oil pressure senders are easy to come by, but I don't know about high pressure versions.

Maybe it's too ambitious and too expensive, so it could be that I'll never get around to it. But is sure does seem like it would be pretty cool if it worked.

Anything else I should consider for monitoring?

Thoughts?

Bob

[DavidBarkey]

Way above my pay grade . But if you can do it and obviously have a good understanding of what is involved . Go for it when you have the time . Life is about trying , not wishing had at least tried .

[Eugen]

@thebuildist Bob, I like the way you think!

I have quite a few thoughts on this idea, will follow up when I got more time. This is the kind of thing I'd have done a few years ago.

5000 psi pressure transducers are $$$$!

[Eugen]

I'm not very fond of dial gauges when it comes to things like temperature or voltage. I'd rather see the number, like 12.3V, and 80C. The beauty of this dial is that you can show multiple things, like a car gauge. You can have a clock hand showing RPM, and voltage and temperature numbers on the bottom part of the display. The fewer button presses the better, IMHO. But you seem fond of the hand on the dial even for voltage and temperature. So, where will you draw the line deciding which voltage is healthy, once the engine is running? This is the reason I added a number display for voltage to my truck, because when the alternator started to have problems, the car computer didn't flag that to me. Once I had the display, I could see that the voltage would sometimes drop to 12.5V, other times 13.1V, when a healthy alternator should be closer to 14V.

I can see why you'd want the hydraulic pressure shown, that's really useful, but the hydraulic oil temperature? Outside of curiousity, what would the usefulness of that be? I'm just wondering, not at all poking at your idea.

BTW, places like newark has a number of 5000 psi transducers, that's where you can get an idea of prices (hundreds). A 5000 psi liquid filled analog gauge is $20.

[thebuildist]

First of all, let me say that this is precisely the kind of feedback that I'm hoping to get. So thanks for your excellent post.

Next an amendment to the above post: I didn't look carefully enough and the tach that I bought for $7 is actually literally mechanical. As in spinning shaft mechanical. So that's not going to work. So I've gone back to the drawing board and just ordered a similar looking tach that uses electrical input like I thought I was getting the first time. That upped to the cost to $15.

I guess I like the analog needle display for a couple reasons. Number one it just looks more legit. Anything that is strictly a seven segment digital display is obviously not more than a couple decades old. And one of the charms of these tractors to me is that they hearken back to a more heavy iron era. So a needle gauge just looks more appropriate to my eye. But more importantly, a needle gauge gives you instant unthinking context. You don't have to read a number and search your mental chart for whether or not that's a good number. You can just see the needle against the background of its acceptable range and instantly know if it's high low or medium. Now the button pushing part is not ideal. I'll admit. But we just don't have much real estate to work with, so I don't see how I could possibly display more than about two gauges at once no matter what.

I suppose what I should do is give it an auto rotate/cycle through mode, and make that the default. So when you start up the tractor it will just sit and cycle through all of its gauges so at any given time you can glance down and see whatever is going on right now. If you'll stare at it for 15 straight seconds, you'll see all the various statuses as they are right now. Then say if you double click the button it'll put it into manual mode and allow you to cycle through one by one and home in on a single gauge type and monitor just that one if you want to. That's the beauty of it being configured in software is that pretty much whatever you can dream up you can make happen.

Now that I think about it, since the battery charging light will now be pointless, I could have it light up that light if any of the various data types are out of range. And that would alert the user that they need to have a look at something.
I'm not sure all of the data types I've mentioned are really relevant. I'm not sure that engine oil temp is relevant. Especially if you know CHT. And I'm not sure that hydraulic oil temp is necessarily meaningful. But if it were more or less free to add on, it might be nice to know.

I went looked on eBay and it turns out I can get a 3,000 PSI transducer for $20. Shipped from China. What's really great about it is that it's advertised as operating on 5 volts. Which means it could be wired straight to the Arduino and not have to have a separate board to drive its voltage up or down so Arduino can read it. For now it's just in my shopping cart so that I don't spend a bunch of money on something I'm not going to actually do.

As far as the ranges for all of these data types it's obviously an arbitrary decision that gets coded into the program. For voltage I might say that the lower boundary is anything below 12. Which indicates that the battery is actually discharging. And upper boundary of say 16. Which indicates that the battery is getting overcharged. But there again that's where the needle gauge shines. I can set my red mark at a value that I know for sure is bad. And as long as the gauge is between the upper and lower boundaries, then I don't need to worry.

But a decision would have to be made for all of the data types. What's the appropriate CHT range? What's the appropriate amperage in and out of the battery? If you do monitor any of the oil temps, what is the appropriate range of temperature?

And that's exactly the kind of conversations I'd hope to have here on this message thread.

[propane1]

Well, way above skill level this stuff. But, I put a gadget on my Case 224 just for fun and entertainment. But, the temperature of the hydraulic oil could be use full. I’m thinking that once I get use to sorta of normal operating hydraulic oil temperature while I’m cutting grass, if the oil cooler becomes plugged up with debris from grass cutting, the temperature will go up and I’ll know to check the oil cooler and clean it out if needed. And while there clean out the engine flywheel screen too.
So my gadget also has rpm. Not really needed. But still information. The other thing my gadget has is an hour meter which can remind you when to do service. I find that good. One of my other tractors has a tach/hour meter in it that reminds you to do service. It’s been in there 17 years now.

Any way. Just a ramble. Not very helpful to you Bob.

Noel

[thebuildist]

Again, nice feedback. In the loader mods I'm making, I'm probably going to abandon my underframe plastic shield. I just don't see what purpose it serves. It looks to me like it must not have any effect on hydro oil temp. But if I monitored my hydro temp, I'd know for sure whether I'm pushing the limits, and I could run the tractor both with and without the shield to see if it matters on my particular machine. So maybe I do deem it to be important.

I guess my Linamar/Onan 20hp has oil pressure? That would probably be more meaningful than oil temp. So maybe I go that route instead.

Of course, if I do get this all built out, I'll share all the plans with everyone, and folks could configure their own gauges with whatever is most meaninful for their specific machine.

Do you know, how does your tach unit pick up the RPM? A wire wrapped around one of the spark plug wires? Or something related to the voltage regulator?


Bob

[propane1]

Mine on my Case 224 and the other one I mentioned are both a wire wrapped around the spark plug wire.
The one I just put on the Case has 9 different ways to set it for your engine type.
I have seen a gadget that looks the same as the one I put on the Case that the rpm was operated by vibration. I didn’t look real close as to how it does that, but I have a hand held vibration tach that I use on stuff. Just has a wire sticking out. It vibrates in a circe when at the right rpm. You adjust the pointer to get the biggest circle, that’s close as you are to the correct rpm.


Noel

[DavidBarkey]

Mine on my Case 224 and the other one I mentioned are both a wire wrapped around the spark plug wire.
The one I just put on the Case has 9 different ways to set it for your engine type.
I have seen a gadget that looks the same as the one I put on the Case that the rpm was operated by vibration. I didn’t look real close as to how it does that, but I have a hand held vibration tach that I use on stuff. Just has a wire sticking out. It vibrates in a circle when at the right rpm. You adjust the pointer to get the biggest circle, that’s close as you are to the correct rpm.


Noel

The same principal as a knock sensor in an auto. Basically as pressure sensor with small weight on it in a housing the fasten to the engine . As the vibration cause the weight to change the pressure against the sensor ,the electrical pulses are read buy a counter chip. That signal is sent to a read out chip for display .

[DavidBarkey]

Again, nice feedback. In the loader mods I'm making, I'm probably going to abandon my underframe plastic shield. I just don't see what purpose it serves. It looks to me like it must not have any effect on hydro oil temp. But if I monitored my hydro temp, I'd know for sure whether I'm pushing the limits, and I could run the tractor both with and without the shield to see if it matters on my particular machine. So maybe I do deem it to be important.

I guess my Linamar/Onan 20hp has oil pressure? That would probably be more meaningful than oil temp. So maybe I go that route instead.

Of course, if I do get this all built out, I'll share all the plans with everyone, and folks could configure their own gauges with whatever is most meaninful for their specific machine.

Do you know, how does your tach unit pick up the RPM? A wire wrapped around one of the spark plug wires? Or something related to the voltage regulator?


Bob

Bob I run a temp gauge on Frankie . As you know we run engine oil in the hydra circuit . I run a electric fan on a manual switch ( have not got to a auto temp switch yet ) . It allows me to let it warm up faster when cold out and as soon as it is up to 140 F i put the fan on . It will then go up to 180F if working hard but never goes beyond that . Which is a good range when you consider an auto engine oil temp will be between 200F and 250F at operating temp.

For a tach sensor . What about using a knock sensor from a car and count pressure spikes ?