Add automatic control to my SUV's air-lift system

Just for clarification... I know that adding air bags does not really increase the load capacity of my SUV.  Mine is rated at 6500 lbs, and my camper's dry weight is 4550.  And I can guarantee that I don't carry more than 2000 lbs of water/propane/batteries/gear, etc... when fully loaded, so I'm not close to or exceeding the tow capacity of my SUV.  Also, I have a weight distribution hitch system, and my SUV has a full frame, like a truck.  But I do like the feel when towing my RV with the air bags installed.  

@iwannastout True, nothing can increase the load capacity, but airbags can keep the vehicle level and make the ride smoother. Keep in mind that the difference between dry weight and fully loaded includes passengers, fuel, water, and basically everything added to the SUV and trailer since they left the factory.

Double-check your tow capacity (that is a marketing term) by looking at the stickers on the driver-side door post. I think it's the yellow sticker, and it is unique per vehicle. It will tell you what your vehicle is rated for; it will never be more than 6500 and can be quite a bit less.

EDIT: I forgot what I wanted to mention, there are devices today to measure actual load on the hitch. I am fairly sure that is what is called a load cell, so you might expand your project to use two of those that is calibrated to determine what your hitch weight and tow weight really is.

Sorry to carry on, I am selling my 42ft 16,000 lb fifth wheel, and already sold my F450 diesel dually so I am fully conversant with all things weighty.

I assume you have LT tires on the SUV, so maybe adding a temperature sensor as you likely already have TPMS.

There are lot's of trailer projects for us electronics nuts, I added LED lighting everywhere with most on mag switches but the under island was using a radar sensor.

Good luck.

Posted by: @iwannastout

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I've been thinking about adding this to my SUV's air-lift system, which are helper air bags that are installed in the rear suspension springs when inflated give me some additional load capacity and stability.  Right now the whole system is manual, there is a Schrader valve that connects to both air bags and has an air pressure gauge.  I can manually inflate and deflate the system by hooking up my battery powered tire inflator or pressing the Schrader valve in to release pressure.  The min pressure for the air-lift system should be 5 PSI, and the max is 35 PSI, which I have to check periodically and add air as needed.  So I had an idea to add a microcontroller, small tire pump, and a solenoid that I could use to automatically control the pressure for towing my RV.  At this point I have most of the parts I need such as a small 12v tire pump, a 12v solenoid valve, dual relay board, air pressure transducer, and some connectors to hook it into the existing air line.  So I have 3 locations on my SUV, let's call them A, B, & C, that I would like to connect together to complete the project.  Location "A" would be a small display to show me the system pressure and perhaps have controls such as up and down and a preset for towing/not-towing.  Location "B" is in the back of the SUV on the driver's side in a compartment where the Schrader valve, analog gauge, and transducer are located.  Location "C" is in the back on the passenger's side where I would install the pump and 12v air solenoid.  I would prefer to just have one microcontroller, to monitor/control the system, but obviously would need to have control wires from B to A, and B to C (assuming the microcontroller was installed in location B).  But it looks like the distance from B to A would exceed the distance for I2C or SPI to a display.  Perhaps location A could be replaced with a small app that I could pull up on my smart phone to replace the controls.  Any thoughts or suggestions?

@iwannastout, Hi, and welcome to the forum!

I was just looking at your proposed project of controlling air bladder bags using MCU ( micro-controller units) and some hardware. Looks interesting from a controls stand point, so I thought I'd jump in and give you some suggestions on how to proceed.

First of all, the solenoid valve you may want to use will require two of them, as you can only use one if it's a 3-way, normally closed, and it would have to be energized all the time in normal operation. See the drawing I have provided below where I use (2) n/c 2-way solenoids at 5 V, 2 watts. However, you can use what ever suits you, and just modify the drawing for 12 v solenoids if you wish. This is in no way recommending any model or manufacture of parts mentioned in the drawing.. it is simply a layout of how you could go about it. If you need more info.. just reply back with my handle @Inst-Tech, and I, or others, will try to help you get your project going.

Have fun, and be safe..

regards,

LouisR

@inst-tech @iwannastout I wish I knew about those small solenoids. The one I used for my main water was much bigger (3/4") and used much more power. I only had one, and it was designed to shut off the water when there was no power. RVs are notorious for failed toilet fill valves that then flood the RV (an RV toilet has no overflow) The only caution I have, and it's so obvious I apologize for mentioning it, is that you will need to either add more relay contacts and/or hardware safety switches OR do it in software, make sure your software is fail-safe, in other words, have the setup code set all devices to the 'safe' position, you don't want both valves open at the same time. Use esp_restart(); for any errors.

Yes, the valves are gas valves so work with air or water.

@zander , Yep.. Most of the valves we used in industry are of the fail safe nature, and normally close is the fail safe for supply, and fail open is the requirement for  pressure relief or blow down.

In this case, the air bladders are not required to deflate on loss of power, or high pressure.. for high pressure function, we would probably use a mechanical relief valve between the pump and the SV-1 valve set 10% below max pressure that the bags are rated for. The software high limit would be 20% of max pressure.

This is such a simple design that only would need a few more nice things like metering valves in the SV-2 exhaust port to control the bleed off, and maybe one in the supply port of the SV-1 to control fill pressure..but the size of the internal ports are very small, so I'm not sure you would even need them. Also an isolating 1/4 turn valves in the line before the SV-2 valve to atmosphere for emergency depressurization of the air bags in case of power failure, or loss of control to the SV-2 exhaust valve.  

regards,

LouisR

@inst-tech I am afraid my bias is showing. Human safety was paramount as a one-time elevator designer, so most of the system was redundancy and safety . Then, when working in the global financial markets, 100% accurate data was the only mark; there was no such thing as an A- let alone an F. I think in the 15 years I worked there we had 1 crash and that software ran 24 hrs a day and almost 7 days a week since we operated across the date line and some jurisdictions operated on their local Sat. The 'good old days'

Even in a worst case scenario here the end result is the vehicle returns to 'normal' operation.

@zander , Yes Indeed..In an operating play that run 24/7 365.. and only down for maintenance about 4 weeks a year, I'd say that safety and reliability were of paramount importance..both to human safety, and equipment reliability. As I was a part of the PPM (preventive, protective maintenance) program, and the Asset manager for control valve technology..that was our main focus. Safety goes hand in hand with efficiency, and reliability.. and your right, nothing should come between safety and proper operation of equipment. The goal here is to start the OP thinking along the lines of how to organize the project, in terms of how the system should work, and then build in all the safety requirements to complete the project.

I hope this winter storm is not to hard on you Canadians.. it's now 26.9 degf down here, and expected to be in the high teens through thursday. We woke up this morning with ice all over the place..We ain't use to that kind of cold, so everything shuts down..no school, most business close, and they advise us to stay off the roads...lol  

Regards,

LouisR

@inst-tech Not sure where you live, but we Canadians are thankful we don't live in Buffalo; they get terrible winter weather. I recall going there to ski in college, and the snowbanks were 13 feet tall! I have never seen more than about 6' here, and I live 8 hours north of Buffalo. Up until about two weeks ago, I was still wearing a T-shirt under my fall jacket. Where we used to live is experiencing quite a patch of bad weather, but tomorrow it will be 39 Hi, climbing to 50 by the 24th. Where I am now is much cooler, with the Hi only climbing to 30. Remember, a huge bunch of Canadians live at a latitude that is within a degree or two of Northern California and even Toronto, the 3rd largest city in the USA and Canada, 4th if we include Mexico is only 1.5 degrees latitude north of the California Oregon border. I think there are 15 US states north of the US-Canada border at Niagara Falls. Maybe a better indicator of our weather is the fact the last 30 days have cost me a total of $33 if I use the average electricity cost. We are a TimeOfUse region, so it varies, but the rate I use to calculate is quite conservative. Do not despair, the heat is coming. When I moved here in 2004 in May it was hot enough to need AC. No one sold AC in this northern town, so June bought one and shipped it to me. We ended up with three small AC units in that lake-side house. I told people the day would come when it hit 40C/104F, and it did while we were visiting the west coast a few years later. A few years after that a town a few hours into the interior of BC hit over 50C/122F and eventually burnt to the ground. Compared to their grandparents, that was 20C/36F higher than they ever experienced. The only good news is the heat kills the Black Flies early in the season and vastly reduces the mosquitoes.

Remember since Dec 21 the days are getting longer, the sun is coming back!

Hi @iwannastout,

 You already have some great advice from others who are familiar with the type of vehicle you are discussing, which I am not, so this is just a single observation, which might not even be relevant.

From your description, it looks like your system is only used for a short time, in advance of a journey, as part of the preparation. If that is the case, then perhaps you could reduce some of the safety concerns by having a master power switch to your automated system, which would only be closed for the short time needed in the preparation phase.

The rationale being a concern that a voltage spike or other unexpected event might trigger the system to start doing something, not necessarily the right thing, whilst you are driving it, or maybe when it is parked unattended. Having a master power switch effectively limits the time when it can activate to periods when you will be alert and able to take any appropriate action, probably including opening the same switch, which obviously needs to suitably placed for easy and safe access.

You would probably have naturally included such a provision, in which case, I hope you don't mind me emphasising it. One of the problems when considering safety is that it is difficult to spot every possible way something can fail. Many possible tragedies can be contained to minor inconveniences, if the design assumes that even the 'very unlikely' failures mode will occur (sooner or later), and provision to accommodate that failure is included.

Best wishes with your project, Dave

@davee Great advice Dave!  Since the air bags are really for load stabilization, their function isn't really that critical. I would include a 1/4 turn ball valve in the air line between the air bags and the exhaust solenoid valve, and an electric emergency switch to override the same valve located in the SUV cab. As you have stated, it's not possible to allow for every contingency and failure that can, and does, occur, but the more likely ones can surely be addressed.

In the industrial realm that I am from, we had a saying, KISS ("keep it simple stupid") as the more complex is system is, the more problems that can, and will occur, do to all the added possible failure nodes. Most all our equipment was designed fail-safe,and that was my job to ensure that it was in compliance with production and safety requirements before we turned it over to production. As many new systems were added over time, we were constantly challenged to inspect, test, and troubleshoot those systems to weed out any possible failure modes.

Now retired since 2014, I don't really miss all that stress...lol, but I do enjoy using my experience to help solve problems that I can relate to.

regards,

LouisR

@zander . Ron... we're located on the Gulf coast, Mobile, Alabama..where for the most part, our weather is mostly on the warm side, Jan. and Feb. are our winter months, and as you see, it can get quite cold, in the teens like it is today .. this morning @ 07:30 CST it was 18 degF!.. but the cold will be out of here by tomorrow, and be back is the 50- 70 degF range as normal for us.

By middle of March, it will be in the 70's, and really warm and humid weather follows...

regards,

LouisR

@inst-tech FYI @davee I am not sure if either of you has ever owned a trailer, so perhaps you should look around at the results of a google.

airbag lift controls

These are standard after-market devices. The latest crop seems to be moving to wireless. 

These are just rubber bags that go between the rear axle and the truck/SUV bed frame to lift the truck/SUV higher if it is squatting due to overloading or to make the suspension less harsh due to heavier loads.

If the worst case happened and the airbags had an unwanted sudden deflation then all that would happen is the normal suspension would take the weight and might result in some noise as the suspension bottomed out. In theory, I guess it might be possible for that sudden deflation to cause a temporary small loss of control, but then so does a blowout and he is much more likely to have a blowout.

Generally speaking, these bags are only adjusted once when the load changes, but large enough temperature changes and more likely elevation changes can necessitate an adjustment. It would be very cool if the OP were adding ambient temperature sensors and/or altitude sensors to make any adjustment automatic. These features may be cool but it's not that big a deal to just check and adjust any time the truck/SUV stops for a fuel or nature break.

@inst-tech Ok, yes, that is cool for you guys. Since I was born and raised further north, my system is comfortable at a much lower temperature. I personally feel uncomfortable starting at about 75/24, depending on the humidity. My favourite time of the year is fall when the temps are 10/50 to 15/59. I played golf in the desert (Scottsdale, AZ) when it was maybe 100, but it was very dry and not as bad. When I went to golf school in Florida, though, it was very humid, and I had to change clothes and shower at lunch break and again at the end of the day before supper. I went through 3 sets of clothes every day. I normally hate playing in the heat, but I did tie the record on that course and led my team to victory, so it wasn't all bad.

Somewhere I have a picture of me making maple syrup in the spring. The sun was shining on me and the temperature needs to cycle between + and - 4 degrees C or 25 and 39 degrees F. What is interesting in that picture is I am wearing shorts and long sleeve shirt. You would likely be shivering, it's just what we get used to. One of the reasons we moved back to the north is that where we were on the coast is getting too hot due to global warming and the fire threat was too much. It will even get so bad here this year I will need to get a second AC unit.

Hi Ron @zander,

I haven't owned a trailer of this type, but I have had both a (UK style/size) caravan and a small (minute by your standards) trailer.

Whilst the tiny trailer is unnoticeable most of the time, the caravan, at about 75% of the mass of the towing car, is fine in normal use, but can be truly terrifying if at say 60 mph, it starts to be 'upset' by something like side-wind, snaking, or a slight 'bump/scrape' from another vehicle.

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I presume any new electrical system would have an enable switch, fuse, etc. So I wasn't suggesting any extra hardware ... basically just a case of positioning and usage to minimise unnecessary risks, no matter how 'unlikely' or 'small'. So assuming the switch is always off when the vehicle is being driven, you can be reasonably sure an electrical/electronic/software problem with the 'auto-inflate' system you recently installed, is not the cause of any issue when you are on the road.

I have no idea of how much an errant airbag inflation, deflation or burst could upset the situation, but I certainly wouldn't want to be anywhere near it when it happens, particularly if it was travelling at speed. I also wouldn't be too keen on explaining to my insurance company afterwards, if there were any consequences, particularly if it involved any third parties. A tyre blowout they would probably accept as bad luck, but some homebrew electronics ..?  🤔 

Just my views ... others are entitled to theirs.

Best wishes and stay safe everyone, Dave