Laser position sensors

Just thought someone might find this interesting.

Have always had issues with the position sensors on my Doron SR2. When they start to fail, they get noisy, which makes the machine move violently, which scares people, and damages the simulator (mechanical structure, joints and especially the 65" 3D TV).

Doron wanted several hundred dollars for replacement original linear (carbon strip) potentiometers. So, instead, I replaced them with magnetostrictive linear position sensors a few years ago... they worked great for a couple years, but they were not as weatherproof as the manufacturer said (grr!), and died from water damage. I felt they were quite expensive (~US$300 ea.) so two years ago I tried these 3D printed string potentiometers.

They worked great. I went with the cheaper wire wound ones, which were essentially 10 turn 10K pots. But again, after only 4 months of operation, the wipers inside the pots (not at the travelling contact, but at the base of the pot where the "rotor" wipes the ground ring) started to wear out.

Last week, I tried to install the magnetic contactless version of these 10 turn pots, but the problem I had was that the internal friction of the pots was so high that the coil springs wouldn't reliably pull the string back in.

So now I'm trying VL53L0X laser position sensors. I mounted an Arduino nano inside each sensor to convert the I2C into 0..5v PWM which is fed through a resistor/capacitor to become the 0 to 5 volts that the motion control card looks for. We'll see how it works.

Hooked up and working. Looks to be some noise on the lines - perhaps I'll look into it, but just the way it is... I haven't seen it move this smooth in years.

seeing stuff like this...

wow, i am very impressed by this DIY community!

i like it, sir

Hello dear colleague, I would like to ask you a question: I have read that you have used the laser sensor for feedback. How did it work? I have tried to see the video of this thread several times but I have not seen the laser sensor.
Can you give me some news?
Thank you

interesting ! price is nice ~10€
I looked for the specification but cannot find precision and error...
range 70 à 80cm up to 200cm
https://www.st.com/resource/en/datasheet/vl53l0x.pdf

Yes, I have seen, it seems that the latency is 30ms.
It would be very interesting to have some answers from Ryanosman, to understand if he has a nice movement, if he is reactive and other and possible operational characteristics on his simulator.

Still using them. I have had a couple failures due to water getting into the mechanism (totally my fault), but yes they work excellent. I forget what the accuracy is... latency is negligible. Reliability is through the roof... (No wearing parts).

My suspicion though, is that if you're trying to designing for realism, you might want a rotary optical sensor for more resolution. My recreational sim is more of an 'arcade' type of scenario. The original carbon strip/wiper sensors had about 100 steps of resolution for the entire travel... The lasers provide much more than that, but an optical encoder will get you (depending on your design) 300,000 steps of resolution.

Hi Ryanosman and thanks for your reply.
Soon I will carry out the laser test, I will use a resolution of 8 bits (1024 positions).
I would like to know, in the videos you published in this post, where did you install the laser? I do not see...
Could you take a video of the laser during operation?

They are in the tubes that you see in the video. The position sensor was at the bottom of the lower tube, and a piece of reflective tape was mounted at the bottom of the upper moving part (the piston)

ok ...
How did you manage to transform I2C into 0 ... 5 Volts?

Ah yes... A dedicated $4 Arduino for each sensor.

Wow, great !! Good boy.
And how do you get the analog values?
Have you written a code?
Can you show the pattern and insert the code?

Hi, for the growth of this Forum, could you share the Arduino nano sketch for the operation of the VL53L0X laser?
And maybe even enter the values of the RC filter (capacitor and resistor).
Thank you

Great remark about latency. 30ms is still acceptable if movemnt commands rate is lomger (in my case it is 100ms), but can be a problem for faster movement. Like you, I am also interesting to get more info from Ryanosman.

Hi all... Sorry for not being more involved... Partly it is because I am quite busy usually. But over the next few days I am in a slow time and should have time to get involved and discuss things.

What questions still want to be answered?

We have a lot of time for these things. so, no problem if you are busy. My idea was using optical sensors as I also expirienced same problems with standard, very expensive and rare linear potentiometers (910 mm) on my simulators. Tried to find less expensive but those also are damaged now after one year exploatation. Latency eliminates most laser types, so your option seems to me very promissing as you mentioned.

Hi, could you share the Arduino nano sketch for operating the VL53L0X laser?
And maybe also enter the values of the RC filter (capacitor and resistor).
Thank you