CTIS and Arduino

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Plasa

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Hello forum.
I am thinking of creating a Arduino hack for the CTIS controller for M1078, first and maybe second generation. I gave a very fast look at the system and seems not really complicated. Does anyone have some information or a workflow diagram, some sensor value or something else that can be usefull for building a cheaper controller? Of course I will then share the sources to anyone, if someone need it...

Christian
 

Plasa

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Hello again.
Please don't misunderstand me. It's not because it is not working, but I like to have a spare part of this component. On web actually I cannot find any seller that sells the controller. This is why I was thinking to make a rebuild of it.

Christian
 

patracy

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I think the Arduino could be used for this certainly. Adapting sensors probably wouldn't be that hard. But you'd probably have to make use of a relay board to power the actual valves. Unless they use PWM. The hardest part is going to be getting the design parameters. The rest is coding to match it and interfacing the 5v logic.

I'm using a mega right now for a sat tracking/control. Using the pwm output to drive two H bridges for directional/speed control of the motors. My input is a mix of GPS and accelerometer data.
 

Awesomeness

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I like to have a spare part of this component. On web actually I cannot find any seller that sells the controller. This is why I was thinking to make a rebuild of it.
Building a microcontroller replacement should be doable. Nothing about the system is overly complicated (e.g. no digital communications to decipher). That said, replacements are easy to find - they're all over eBay and other online sites.
 

Ronmar

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My CTIS is bricked(5 solid LED’s) so I am working on a electric over pneumatic manual control right now. It should be very do-able with a programmable microprocessor. The hardest part will be interfacing and interpreting the speed and pressure transducer signals. IMO, Nothing fancy in the control of the solenoids was employed. They are simply turned on or off. By using the valve design that they employed in the PCU it requires a combination of two valves to operate properly. This makes it far less likley that a single short circuit could over-inflate the tires(Extremely dangerous). My testing determined the following(all pressures taken from the transducer port on the PCU):

Control by itself: Slowly adds pressure to the tire plumbing, the QR valves dump briefly until they get enough pressure to close then you see tire pressure on the transducer port. Takes 20+ seconds to get to that point though.

Supply by itself: Pressure jumps to about 40, then decreases to around 5 PSI and front QR valve starts dumping tire pressure. I currently have a bare chassis with no real weight on the back, so this may have something to do with only the front QR really dumping.

Deflate by itself: Nothing, solenoid activity only, no air is moved.

After playing around with it for a bit I came across the following:
To check pressure: Activate control and momentarilly activate supply to jump the pressure in the plumbing past the QR release point and open the wheel valves. Tire pressure will be read on the sensor port as long as the Control solenoid is maintained. Transducer port pressure was within 1-2 PSI of the tire pressure measured at the tires every time I checked it. This also equalizes the pressure in all 4 tires as they are all connected to each other. When the solenoid is released, the PCU vents axle/system pressure quickly, closing all the valves.

To inflate: Activate Control and Supply simultaneously. Pressure on the port jumps to around 85 PSI then down to about 5 PSI above the tire pressure as the wheel valves open and start taking air. Pressure on the port leads the tires by up to 5 PSI while filling. Filling of course is subject to the availability from the wet tank protection valve so it takes a while to inflate, especially at idle. To check pressure, release supply only and actual tire pressure is read on the port as long as the control solenoid is maintained. Re-activate supply to resume filling. Releasing both the solenoids purges the system pressure quickly and closes the wheel and QR valves without dumping.

To deflate: Activate Control and Deflate simultaneously. Pressure rises to around 8-10 PSI on the port, and both QR valves open deflating all tires equally...

I removed the pressure transducer(port is 1/8” NPT) and installed an adapter and hose from a 0-100 PSI automotive oil pressure gauge. I use 3 pushbuttons to control the solenoids, with the control pushbutton supplying power to the other two buttons so those solenoids cannot even be activated without activating control... The control button will also turn on the gauge light but I havnt wired that yet as I need to put together a 24V LED. I gutted my bad ECU and put the gauge and buttons there so I can use the power supplied to the ECU from the cannon plug. No real modifications so I can go back to an ECU by simply re-installing the pressure transducer, and a working ECU. I will write about it in the Manual CTIS thread with pics when I get it all put back together this weekend...
 
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Plasa

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Sounds very intresting. Thank you very much for the information!
@Ronmar: I will be more than happy if you share some pics and info about your solution. Thank you very much!
I would like to have a system like the original ECU, where you can select the ground type, maybe with display to see the settings and the status. And if possible use the old chase of the ECU to keep existing wiring etc... If I start the journey I will keep you informed!

Christian
 

m-35tom

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I also thought about doing a replacement system with Arduino. Very simple and variety of displays available to show actual tire pressure etc. I have boards made in China for many of my products and can easily go from schematic to CAM Gerber files if you need it. (control circuit etc, I would not use relays, switching by transistor)
 
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Plasa

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Why not relays? Using some industrial relay is more reliable than PWM, and in emergency can control manually...

Christian

I also thought about doing a replacement system with Arduino. Very simple and variety of displays available to show actual tire pressure etc. I have boards made in China for many of my products and can easily go from schematic to CAM Gerber files if you need it. (control circuit etc, I would not use relays)
 

spankybear

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Why not relays? Using some industrial relay is more reliable than PWM, and in emergency can control manually...

Christian
Industrial electronic tech here... From my experience relays can't hold a candle to PWM when it comes to reliability... Plus you can do countless things with PWM than you can with a relay... what can only do one thing. Kind of like apples to rocks...
 

patracy

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Industrial electronic tech here... From my experience relays can't hold a candle to PWM when it comes to reliability... Plus you can do countless things with PWM than you can with a relay... what can only do one thing. Kind of like apples to rocks...
Agreed completely. Also note, there's a LOT of PWM being used in automotive applications these days.
 

Awesomeness

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Industrial electronic tech here... From my experience relays can't hold a candle to PWM when it comes to reliability... Plus you can do countless things with PWM than you can with a relay... what can only do one thing. Kind of like apples to rocks...
I don't understand what you're wanting to do with PWM. You're controlling simple solenoid valves and stuff... turn them on to fill, turn them off to stop, take a pressure reading. We're not trying to communicate to anything, or control positioners, or anything fancy. Can you elaborate on exactly you're wanting to do?
 

spankybear

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I don't understand what you're wanting to do with PWM. You're controlling simple solenoid valves and stuff... turn them on to fill, turn them off to stop, take a pressure reading. We're not trying to communicate to anything, or control positioners, or anything fancy. Can you elaborate on exactly you're wanting to do?
I was replying that some said a relay was more reliable than PWM. As to want you want to use PWM for... well I can't say in this instance. However you could use PWM to control pressure. Also duty cycle but I don't think this is an issue in this case.
 

yertnamreg

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PWM is a type of digital signal used to convey information (typically a percentage). A relay is a type of output circuit. PWMs are typically hooked up to some type of transistor based output circuit which when properly designed is more reliable than it's relay counterpart.

I don't have any info on the solenoid valves in the CTIS, but as far as I know they are standard solenoid valves (i.e. they are either on or off). Driving these with a PWM signal could have unpredictable results. Proportional solenoid valves are what are typically driven with a PWM.

Hope that helps to clear things up. I are an electrical engineer :)
 
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Sounds very intresting. Thank you very much for the information!
@Ronmar: I will be more than happy if you share some pics and info about your solution. Thank you very much!
I would like to have a system like the original ECU, where you can select the ground type, maybe with display to see the settings and the status. And if possible use the old chase of the ECU to keep existing wiring etc... If I start the journey I will keep you informed!

Christian
Oh boy. 74m and I had done some similar work on this (mine on the various 5-ton versions) about a year and a half ago, and both put the project down before finishing. He was just interfacing the ECU to a computer for settings, and I was building a monitor for a working system off The CAN version. We both might be able to help out in some of the wiring / signals coming back from the other sensors, etc. Time to get off my butt and help. Great information above on how the system works at the pneumatic level. My monitor is Arduino based as well, so could be adopted, but I was using CAN...
 

Plasa

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Hello again.
I'm moving on, the software itself is near ready to use... A quick question about the PCU solenoids: On a M1078 are they 12V or 24V? If the hole system is 24V I think they should be also 24V. Someone have the correct voltage? I search on the other threads but nowhere exact info...

What I develop for now:
- Airtank pressure, if closes wait for 5 seconds before starting check
- you can select 4 terrains: emergency, sand, XC and highway. The PSI are configurable inside the sketch
- control valve opens, after 2 seconds inflate valve for 2 seconds, to check pressure for 30 seconds
- Arduino decide if inflate or deflate
- every 20 seconds Arduino checks (by closing the inflate / deflate valve) pressure and stops or continues
- after 30 minutes (inflate) or 20 minutes (deflate) stops due timeout. it can restarted again by selecting a terrain
- Arduino checks if pressure is too low or too high (transducer error) and ambient pressure (if wheel valves do not close)
- if pressure is reached after 30 seconds the system do a recheck of the pressure, and inflate / deflate again if necessary. Otherwise goes to standby and do a recheck after 30 minutes...

All intervalls are configurable on the sketch, maybe for later I will add a eeprom to save pressure defaults and timings.

Status and selection is done by a LCD, selection by membrane touchpad. The new ECU itself have the same connector as the old ECU, I change only the transducer with a 150PSI transducer max 5V DC. I must test the hole setting now in the truck, need to wait for the enclosure to test it...

What is missing are the speed control and overspeed warning. Do someone know how to read the speed sensor? Do I forget something about the functional flowchart?

Christian
 

m-35tom

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Can you furnish the sketch to me? I will look at the speed sensor but it should be very simple once I record the speed/pulses info. Will you be making circuit boards for this? I have a lot of experience making them very cheaply so if I can help, PM me. I have new membrane panels for the old ECU for replacement of damaged ones, and have the dome switch parts as well.
Tom
 
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