project: w220 driver adjustable height sensors
07-02-2014, 05:11 PM
#26
Senior Member
Thread Starter
I am also an electronics designer. I work in aircraft on some control systems like this. I am thinking about trying something similar on my GL320. I have had great luck with a bluetooth 4.0 chip on some other projects and I was wondering...
would something like this need a controller in the car or would it be enough to pull up an app on your phone and change the ride height or would it be preferable to have controls in the cabin?
Is there any resistance to the sensors or do they move freely?
I was thinking a weatherproof linear actuator like we use on aircraft would be a lot more reliable (yes it would cost more) but it is rigid at a single position and you have to command movement. Most of them have a RVDT or something to read the position that would be really handy to verify that all 4 actuators were in the right position.
I think the linear actuators would provide a lot better reliability.
would something like this need a controller in the car or would it be enough to pull up an app on your phone and change the ride height or would it be preferable to have controls in the cabin?
Is there any resistance to the sensors or do they move freely?
I was thinking a weatherproof linear actuator like we use on aircraft would be a lot more reliable (yes it would cost more) but it is rigid at a single position and you have to command movement. Most of them have a RVDT or something to read the position that would be really handy to verify that all 4 actuators were in the right position.
I think the linear actuators would provide a lot better reliability.
07-02-2014, 05:34 PM
#27
You are correct, aircraft linear actuators with a feedback loop would be more robust and could manipulate the Airmatic height sensors with a high degree of accuracy. How you want to control them is a user preference. It should be noted, like static adjustable links, this method fools the Airmatic system to change ride height. There are other electronic solutions that do not need any additional mechanical hardware, such as lowering modules and STAR reprogramming.
It also looks like the car won't ride in lifted mode if you go over 45mph or so.
07-05-2014, 11:44 PM
#28
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2004 S600 Twin Turbo V12
What is the nature of the signal from the actual ride height sensor?
Is it a DC voltage between 0 and 5 volts?
If so, perhaps you could intercept the signals from the sensors, use an op-amp circuit to offset their signal voltage up or down by an adjustable amount, then feed the shifted voltages on into the control module.
Mind that your shifted signals stay within 0 to 5 volts (or whatever range is proper) so as not to damage the control module inputs.
That way, you wouldn't need to add any mechanical devices.
It could be done 100% with electronics, yielding much higher reliability.
Optionally, instead of front and rear controls, one control could adjust all four corners collectively, while a second control could adjust the front / rear heights relatively.
Is it a DC voltage between 0 and 5 volts?
If so, perhaps you could intercept the signals from the sensors, use an op-amp circuit to offset their signal voltage up or down by an adjustable amount, then feed the shifted voltages on into the control module.
Mind that your shifted signals stay within 0 to 5 volts (or whatever range is proper) so as not to damage the control module inputs.
That way, you wouldn't need to add any mechanical devices.
It could be done 100% with electronics, yielding much higher reliability.
Optionally, instead of front and rear controls, one control could adjust all four corners collectively, while a second control could adjust the front / rear heights relatively.
07-06-2014, 12:43 AM
#29
Senior Member
Thread Starter
drewk88 - Yes, anything is possible if your omit the height sensors altogether. I did not research the actual signal output of the sensors themselves. I went with an all mechanical solution because part of the Airmatic setup is to automatically adjust height by load. If I set my ride height it will remain that way even with more passengers and luggage. Also I wanted to ensure that I could replace my servo links with the OEM links in case of some of issue I caused. I wanted my setup to be the least obtrusive to the original Airmatic system.
07-06-2014, 10:08 AM
#30
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2004 S600 Twin Turbo V12
Rob, I wasn't suggesting that you omit the ride height sensors.
Your solution uses a mechanical means to shift their output signal.
My suggestion was to do the same thing electronically, without your mechanical additions.
The end result should be the same for either method, but losing the extra mechanical parts would improve the reliability of system.
Your solution uses a mechanical means to shift their output signal.
My suggestion was to do the same thing electronically, without your mechanical additions.
The end result should be the same for either method, but losing the extra mechanical parts would improve the reliability of system.
07-06-2014, 04:07 PM
#31
Senior Member
Thread Starter
Understood and thanks for your description. At one point in time, I did want to something like this, but I also did not want to hook into the actual Airmatic wiring for risk of damaging something from my end. And you are correct, mechanical changes complicate things and there is more change of failure. If you figure out what the sensor is output is, please let me know. If it is only a voltage reference, then things could get real simple. 
07-07-2014, 03:19 PM
#32
Well.... if it was on an airplane it would be an RVDT or Resolver. Based on what I have seen on cars I would guess an encoder. There are other ways to measure a rotational position but those are the most accurate and reliable.
07-08-2014, 06:40 AM
#33
Sounds like we have a lot of engineers here - c'mon guys please build a simple to install all electronic system so we can manually control our air suspension
The value of the w220 will then skyrocket as all the VIP stance builders will start buying w220s to avoid having to add $3000 of air suspension components to a car
The value of the w220 will then skyrocket as all the VIP stance builders will start buying w220s to avoid having to add $3000 of air suspension components to a car
09-05-2014, 08:56 AM
#35
FYI.... I got my MB Star setup and lowering from there works really well.... I have a GL320 and I lowered it almost 2". Just thought I would give you guys an update. The "calibration" screen on DAS gives you control of each wheel and you use F3-F10 to raise/lower each wheel. It's really cool.
12-02-2014, 09:55 PM
#36
Senior Member
Thread Starter
Quick update:
* Front servos have been installed almost 2 years and have worked with no issue. I had mounted them non-powered for about 2 months to ensure that arms did not move under driving conditions during my trial/error process.
* Rear servo - has been replaced 3 times. The mounting point and the natural servo rotational motion cause binding under certain conditions. As indicated in previous posts linear action would probably be better. For the 3rd servo attempt, I am using a standard size servo (not mini) and use a "servo saver" on the actuating arm. But the root cause of my problem has to do with the geometry between the servo arm and the original height sensor arm. I changed the pick up point on the original height sensor had to notch out part of the cross member near the sway bar mount. I will try to post more pictures in the near future but the range of adjustment has increased. The lowest point that can be achieved now can be seen as the top of the rear tire can be covered by the fender. And the rear can be raised higher that the stock height.
* Front servos have been installed almost 2 years and have worked with no issue. I had mounted them non-powered for about 2 months to ensure that arms did not move under driving conditions during my trial/error process.
* Rear servo - has been replaced 3 times. The mounting point and the natural servo rotational motion cause binding under certain conditions. As indicated in previous posts linear action would probably be better. For the 3rd servo attempt, I am using a standard size servo (not mini) and use a "servo saver" on the actuating arm. But the root cause of my problem has to do with the geometry between the servo arm and the original height sensor arm. I changed the pick up point on the original height sensor had to notch out part of the cross member near the sway bar mount. I will try to post more pictures in the near future but the range of adjustment has increased. The lowest point that can be achieved now can be seen as the top of the rear tire can be covered by the fender. And the rear can be raised higher that the stock height.
12-03-2014, 03:35 AM
#37
What I would give to have an affordable electronic control of my suspension to slam it at car shows and raise it up for normal driving
The renntech/brabus etc lowering modules are not affordable and are not designed for easy adjustment from the drivers seat
The renntech/brabus etc lowering modules are not affordable and are not designed for easy adjustment from the drivers seat
