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I disassembled and reassembled the faulty transducer. Nothing visibly wrong but it must be the circuit board is fried. They say the NEMA case can be installed at any angle but what I found is that the hole in the conduit pipe threading where the electrical pigtail comes out is not watertight and leads directly to the circuit board. I don’t think that caused the failure in my case but it is worth point out for others that find this article.

I also tried switching to the second set of in/out ports thinking maybe one side is completely clogged – no dice. So I ordered a less expensive replacement (although the 900X is still readily available, I opted to try the 500X series). The mechanism is electromagnetic instead of a piezoelectric. It also wastes less air and has more known variables like the relief CFM rate. I hope I don’t like it too much and want to replace the remaining three 900X units!

I left off on Saturday with the two roll transducers working sporadically after centering the calibration screws. I bought an air pressure gauge but my old one is just as accurate so I think I will take the new one back to Home Depot.

This evening I booted up and behold – the right roll transducer was working good! I did a field calibration on it but it wasn’t far off. I couldn’t get the left one to work. It is sporadic. If I apply signal voltage it will start pushing air but if I turn off the signal it will not stop. Span calibration seemed to have no effect. Zero calibration was sporadic (kept getting a pressure signal with no signal voltage).

I ordered a 500-EH replacement from the Valve Store Online. Good prices, reasonable shipping rates, and they even take PayPal. The 500-EH only has a 12ma at +10V lead and ground (no supply voltage loop). Also, the air consumption is next to nothing. The mechanism is different than the other ones but it will let me go up to 145 PSI if I wanted to. Depending on how much I love this new unit I will look forward to replacing the old ones when the time comes.

Finally, the control program. It isn’t smart enough. I basically need the autopilot kind of trend analysis and trim logic for the platform. If it is off balance it never fully recovers to level… ever. So I guess I will work on that while the new transducer is on it’s way. EDD is 5/7.

Weather was uncooperative – I kept having to tarp the top of the platform to protect the computer, power supply, and boards from rain.

Ultimately I got the pitch transducers to work correctly after cleaning the orifice on the rear one but I am having trouble still with the two roll transducers.

I think it is a calibration issue because someone (me) messed with zero and span settings. I reset them to the middle of each pot according to the factory instructions but I need a pressure gauge to do the rest of the calibration (on order).

Finally, the laptop wasn’t able to run the test bench, two webcams, and the screen recorder without running out of memory so all I was able to collect is this short clip. I will probably have to use the actual avionics machine instead of this old field laptop for future tests.

[youtube http://www.youtube.com/watch/?v=AuJzB6hnY4o]

Over the weekend I had some time to play with the anti-yaw mechanism. There is little guidance regarding this important piece of the 3DOF puzzle available on the internet. There indeed is a lot of force exerted on this mechanism so I am glad I sprung for the 3.5″ bore clevis mount. I am not sure that 3/4″ 5-ply floorboard is going to be strong enough (it wants to twist a little if I put some weight on it). Maybe putting another one on the back of the platform or replacing this one with plate metal would work (would have to get it machined).

Unfortunately this configuration doesn’t allow the platform to pitch down to the degree allowed by the actuators. Back to the drawing board!

[youtube http://www.youtube.com/watch/?v=u9JmkxoqeLY]

I wrote about this little USB tilt sensor I found back in October.

I am not recommending this unit for purposes of motion control. The unit firmly affixed to a desk shows a +/- 5 degree variance which would A) require some kind of algorithm to smooth the input and B) make it off by 5 degrees at any given time. The effect I am seeing in my computer models is an oscillation due to latency  and the existing error.

I am very pleased with the D/A controller I got from Phidgets and stumbled upon the fact that they also sell a tilt sensor that is marketed more as an accelerometer.

I have one on the way and plan to play with the code on the next rainy day.

Moving right along, I attached a new picture of the platform with the plywood sheathing completed.

I have since put fiberglass batting in the cavities and installed the 1/2 plywood floor where Ferro’s feet go. Next step is painting/weatherizing the parts exposed outside. Finally I have to drill the holes for the universal joints. Then I need to find 2 or 3 people to help me carry it and lift it into position!

Half the plywood sheathing is on so I started insulating the left side avionics compartment with rigid foam.