Budget Compact 6DOF Universal VR Flight / Racing rig - MSFS, SMC3, FlyPT, Transducers, Controls

Now that the metal brackets are ready, I have attached 5 of 6 motors to the base. I need to take the last motor with me to a friend for fabricating the motor arms



Next, the Electronics Control Box. Planning the layout:


Soldering and connecting components:


Yes, I know my soldering is not good, but those thick wires really suck away the heat, so they are difficult to solder. It looks lumpy, but the contact is really solid. I will insulate it later, of course.


Gluing on the radiators for the motor drivers with a thermal transfer tape:


Soldering the rectifier diodes:

First power-on test, checking the motor load displays:


Almost done:


We've got power!

Here's a video of the first powered test! No sparks, no smoke, so I deem it a success. I connected a single motor and used the self-test buttons of one of the drivers, to make sure the motor was moving. So far so good.

Next, I will design and 3D-print hall sensor brackets and magnet holders, flash the Arduinos with SMC3 and connect the motors. Then I will do the initial calibration. Hopefully next week I will be able to water-jet-cut motor arms, so I can assemble everything, and start tuning the platform. Lots of work to be done.

Looking through your thread I think the motor mount will be too weak, 250W motors are really strong , below is a picture of the M8 rod that was bent today in my 2DOF

I would suggest bolting the mount on both sides with the addition of a steel washer on the underside of the frame

I see what you mean. But to bolt through a 2x4 lumber I'd need really long bolts, and the location wouldn't work well on the underside of the frame. 5 long wood screws hold with a lot of force. I'm afraid that if that's not enough, the wood itself will not be strong enough, or the joints between the frame elements will give. I'll see how it holds on. If it needs reinforcing, there may be other options. i.e. adding 2 vertical metal brackets on the outside that run vertically along the outer wall of the 2x4. Or adding a mirror-image corner bracket and an additional piece of 2x4 on the 0utside to fix it on with another 5 screws.

Got the ECB fully wired and did a preliminary configuration. Arduinos are flashed with SMC3. Things are all connected and powered up. This is the first power-up with live power to the motors and hall sensors installed and configured. Things are not working properly yet and I have issues to solve, but we're getting there!

The most important issue is noisy data from the hall sensors. I need to figure out where does the noise come from and how to isolate it. I know the same setup is working perfectly in my 2DOF. There is also some crosstalk so when one motor moves, the one next to it twitches slightly.
Here's a detailed thread about the issue in the QnA forum.

Here's the video of the first test:


The base with the ECB connected:


ECB with working cooling:


Some motors are struggling to keep in place - that's what the noise is coming from:


The inner mess:

Thanks. The VGA cables I used are shielded and have 1 ferrite magnet remaining, but they do carry ground, voltage and signal and are split at the ends for the last 30cm. Should I try to use a separate shielded cable just for the signal back from the sensor? So like get the voltage and ground there on a normal cable, and signal back on a shielded one (no ground at all)? Or signal + grounded shield on the reverse cable?
I could try using an audio cable for that maybe.

I made a post about the issue here with photos and a video.

Did you connect all three with that cable - i.e. 5V, ground and signal, or only routed return signal through the audio wire?

Did you use the audio cable shield for ground, the way it's used in audio? then 2 inner wires would be +5V and return signal...

Yes, noisy signals from the hall sensors could mean that

1. The signal path from the sensor to the CPU (cables) suffers from interference, or
2. The hall sensor itself picks up noisy magnetic fields (generated by the motor windings or high current cables nearby)

To check wether 1 or 2 is true replace the hall sensors by resistive potentiometers. If the problem goes away it was #2.

Also try to test the pots without all these LCD working, only the pots and arduino running, one by one, to see if the noise persists. Which version of SMC3 and/or Arduino sketch are you using?

It's going to be just easier to replace the wires anyway. They are shielded in the center part, however, they run close to the power wires, and they are not shielded right next to motors, where the windings are (last 20-30cm), and first 10cm next to the Arduinos. Each pair of motors/sensors also shares power and ground and the signal wires run next to each other, and I noticed the crosstalk between pairs of motors. I will replace them with twisted+shielded audio cables I found in my cable stash, and run them on the outside to keep away from power cables, each sensor completely separately and shielded all the way to the Arduino. I will also pot ferrite cores around the cables, and maybe a 1-10mF capacitors if I have suitable ones. We'll see where it gets me. I'm invested in this system so I need to make it work. Same sensors work well in my 2DOF but it has different motors, so there may be less interference.

The noise only persists with motors running. If 24V power is off and only USB+Arduinos+Sensors are running, the signal is very clean. I'm using SMC3 2.10 (soft start/stop) with my own modifications for emergency stop across all boards and some other things planned. Is there a better one recommended for 6DOF?

Wire-to-wire crosstalk (via electromagnetic fields) is only one possibility of EMI. Another is ground-bounce. If your power electronics share ground wires with the sensor signal path then current flowing through the wire leads to small voltage differences of the "local" ground points. For example 10A flowing through a 0.05 Ohm wire creates a voltage difference of 0.5V between the battery ground and the ground terminal of the power stage. If the arduinos are connected to different ground terminals they see fluctuations of the input signals even if the sensor output itself doesn't change.

This gets even worse if high frequencies are involved. A wire not only has a DC resistance but a few nH of inductance can create a much higher AC resistance (called impedance or reactance).

So if shielding of the cables doesn't help it's most likely a ground bounce problem.

Separating the sensor signal path completely from the power wires can help.

Thanks, great advice. How would I do that though? I tried to keep the ground separate for the Arduinos in general, I tried feeding 12V power to them via VIN but that got me weird results (like fans spinning when all power was off, i.e. Arduinos were powering the fans so VIN became a power output when not provided with voltage?) so I only left the USB power. But I think the Cytron motor drivers connected to the Arduinos use shared ground with the high-power feed, because I can see that all ground is connected now, despite my attempts to keep the Arduinos separate from the 24V and 12V circuits. Is there a way to completely isolate the sensor signal/ground?

The fans spin because the 5V fro the USB is back-feeding into the 12V supply. A diode could stop this.

But seperating the power and signal ground is not easy. Professional motor controllers for industrial use have optocouplers at all IO signals for this purpose but the cheap ones like BTS and cytron drivers don't. Grounding with multiple Boards with USB ports is a mess because they all create a loop with the PC.

But at least you could keep the three wires to the hall sensors (+5V, signal and ground) completely seperate from anything else and connect them directly to the corresponding Arduino.

Sorry, I don't know why I believed you are using Sabertooth drivers and them have a dedicated smc3 version. With it there is a communication speed configuration that droves me crazy with similar noise problems but is not your case, sorry