Hello!
After lurking for some time, I decided to show the Joystick that I am working on.
As my last attempt of building a Joystick with a cam-mechanism didn't work out as planned, I tried to create a force-sensitive Joystick using strain gauges.
Some pictures (please excuse the quality, I have only my phone to take pictures):
The prototype (the design of the grip was a bit rushed and is too small):
This is the rod with attached strain gauges (only one pair connected to a cable yet):
A look on the electronics:
Each pair of strain-gauges is connected to a Wheatstone bridge (top left). The bridge-signal is amplified with an instrument amplifier (lower middle) and then read using differential analog-digital converters (upper and lower right) which are connected to the Arduino via an SPI-bus.
The force needed for maximum deflection is 6 N, but I have to check my calculations as that seems quite low (the real F-16 stick has up to 75 N to 140 N depending on the axis, although it is reported as being quite a handful to actuate).
It works surprisingly well, but as I have the electrical circuit built on a breadboard (the final version will have a pcb) the trimmers for adjusting the bridge are a bit loose and have to be adjusted every time before I use the stick. Another Problem is a small creep in one axis over time which I think could either be an electrical fault or a fault of one strain gauge. I can even fly helicopters as bad as I do with my other Joystick (a
Logitech Extreme Pro 3d, so not much of a reference), as there is nearly no noticeable axis-bleed, which I had read about as being a problem with force-sensing sticks.
The next step is designing an adapter for the grip of an TM Cougar, which I hopefully receive next week.
I plan to upload the schematics once the design of the PCB is finished, but that could take a while.
Cheers,
Bernd
PS: If there is interest I can write a bit about the details of how it works.