Automatic Leveling System

[Len Silva]

I built this system for my 4104 about twelve years ago. I had to figure out all over again how it works.  It's really not as complicated as it looks.  Here is the circuit explanation.

I wanted to use just diodes and relays for the logic, as that was the best I could do at the time.  The way this works is that when activated, it first dumps all the air from the bags and then raises each corner as necessary.  This gives me maximum adjustment and lowers the coach for easy access.

The system requires a total of twelve two-way solenoid valves, three at each corner.  They are called HIWAY, RAISE and LOWER.

The HIWAY valve connects the original leveling valve to the air beam.  These valves are arranged so that when no voltage is applied, they are all closed.

The RAISE valve puts air into the beam and the LOWER valve exhausts to the atmosphere.

When switch S1 is in the HIWAY position, the HIWAY solenoid valves are energized for normal travel.

When switch S1 is in the PARK position, voltage goes to S2. When S2 is in the MANUAL position, switches S5 thru S8 are used to manually raise and lower the coach.

When switch S2 is in the AUTOMATIC position is when it really gets interesting.

Power is applied to the coil of K2 by the four normally closed pressure switches, S9 thru S12. These are fed from each airbeam.  K2-A prevents K1 from operating until all four pressure switches go open.

When K2 is released, K1 is operated and latched thru K1-A.  K1-B then operates K3.

The START/RESET switch is needed because it is possible for K1 to operate and latch in the instant power is applied and before K2 has time to operate.

The AUTO-LOWER DEFEAT switch stops the lowering process before all the air is exhausted if desired.

When K3 is operated, the level switches S13 A-D apply voltage to the RAISE solenoids as required.  When the last contact on the level switch goes open, the coach is level.

At that point, the main switch S1 can be turned OFF and all valves will be closed. The coach should maintain level.

I tried all kinds of experiments for the level switch, using mercury switches and ball switches but was never really successful.  Everything else worked very well.

I think that HWH has a level switch they use in their hydraulic systems that would work.

A pdf file of the schematic can be found here:
http://www.lenstudio.com/site/images/BUSLEVEL.pdf

[Ross]

US Digital has an inclinometer that works nicely with a PIC microcontroller.  Two of them connected to a PIC and a few lines of code would make a nice automatic leveling system.

http://www.usdigital.com/products/incremental-inclinometers.shtml

Ross

[JohnEd]

Len,

The only thing missing is a parts list and then even I could duplicate it.  Even if you don't have numbers I would appreciate some description of the part so I could search.  D1-D8 are carrying how much current and are rated for what reverse voltage?

I feel like I am looking a gift horse in the ......  I don't mean to appear ungratefull.  Honest!

Thank you,

John

[Frank @ TX]

Len,
Mine works great and only has ONE part,....... a flux capacitor.
I'm sure you can find them on Ebay.
Frank

[Len Silva]

John,

Frankly, I don't remember, probably whatever was in my junk box.  I'd say 50 volt, 6 amp, common at Radio Shack.

The valves were MAC but any 12 volt Skinner type will work.  I located the HIWAY valve right at the air beam and the others up front.  I think now, I would put all of them at the airbeam.  All that 1/4" tubing slows everything down.

The 4PDT relay was also a Radio Shack item, don't know if they still have it.

My bus hasn't been used for several years now, but the leveling system worked well. I never was quite happy with the various home built level switches I made but the HWH switch in my motor home works well and I think would do the job.  Don't lnow what it costs.

Good luck, hope it works out for you.

Len

[RTS/Daytona]

caution "skinner" type valve are usually diaphragm valves - they are - DIRECTIONAL- only meant to hold pressure from flowing in ONE direction only - if you reverse the direction the diaphragm seat blow open

So they are OK for the lowing function (that's always one way)

but when used for raising - whenever the suspension supply side goes away (the tanks leak down over night- so will the air bags)

The same (leak back past the valve seat in the opposite direction ) is true for the isolation valves that, while in CAMPSITE mode - prevents the height adjusting valves from effecting the airbags.

Thats why I use balanced poppet (OMNI-DIRECTIONAL) valves in the leveling systems I sell

see my G4 or G5 leveling systems at --> http://community.webshots.com/user/hawk_ii

Pete RTS/Daytona

[Len Silva]

Pete,

That's good to know.  Happens that the MAC valves I bought were omni-directional.  Your setup is just about the same as mine except for my attempt at automation, for no practical reason except that I enjoy playing with stuff like that.

Len