I was wondering if anyone has tips on components for an Arc-like encoder? I’m after a smooth, super low-friction turn with reasonably high resolution and switch. Ideally also the component has solved the mechanical aspects like ball bearings and a shaft to mount a dial/knob to.
I’ve used optical encoders like this:
…which get pretty close, but I’m hoping for something with a lower height and with a switch.
from the bom, mouser has the optical encoder 652-EM14R0D-M20L064S, with switch
This part from Bourns is the one used in @TheSlowGrowth’s arc clone, one of which I built recently and can confirm they are excellent encoders, if expensive. They have a little bit of wobble, but are fairly compact, have a great-feeling switch, and generally turn beautifully.
Fantastic, thank you both!
you might also want to look into Hall-effect encoders, which I’ve used very successfully in a project. The one I used took the form of a SOIC-8 package IC. If you suspend a small button magnet, polarised longitudinally - that is important - a few mm above the chip, you can detect the orientation of the magnet to 8 bits of precision (ie, between 0 and 4096). It’s a cheap solution, but makes for more mechanical complexity - it’s up to you to sort out bearings and mechanics.
Speaking of hall-effect encoders, this is a really cool open source hardware project:
The sensing of the scratch wheel is handled by an Austria Microsystems AS5601 magnetic rotary sensor
Jogwheel parts - The jogwheel itself is a gold-plated PCB, available in hardware/gerbers/Jog Wheel. Mine is made from 0.6mm thick board, you can choose the thickness you prefer. You’ll also need M8 bearing/hex bolt/nuts/washers, and a diametrically polarized magnet from https://www.kjmagnetics.com/proddetail.asp?prod=D42DIA-N52. The bearing I used is available at https://uk.rs-online.com/web/p/ball-bearings/6189957/
I’ve skipped to the part of the build video where he starts talking about the jogwheel:
And the final result:
Fun fact: the Haken Continuum also uses Hall effect sensors:
yep! the AS5601 is what I used. it’s… really remarkable how precise and fast it is.
Totally off-topic (for which I sort of apologise) but Andy (my mate who created the SC1000 from ahem “scratch”) also achieved fame recently for this
I guess you’ve all seen the hard disk platter conversions too:
Even showing up in the timeFrog sequencer: http://www.undeadinst.com/products/timefrog
For my own sake though I was wanting to avoid as much mechanical engineering as possible and find the ideal off-the-shelf component. I also got an arcade spinner (https://www.ultimarc.com/SpinTrak.html) which has a nice weighted action that allows for inertial spinning. At the end of the day though it’s just an optical encoder.
Here are the aforementioned optical encoders at work with Neopixel rings. Not actually sending any data, just feedback between encoders and LEDs.
Which ones are these again (part number?)
It’s described as the CNIKESIN 600 Pulse Incremental Photoelectric Rotary Encoder. It has a very smooth, low-friction ball-bearing movement. Recommended, if you can live without a switch and don’t mind the depth (the body alone is 35mm high).
FWIW - its unlikely to find a high resolution encoder like the one used in the current generation of Arc that has a switch. Mostly because they use a separate encoder wheel with sensor setup and not a fully enclosed (self-contained) “module” (like the one you pictured)
Similar question, but does anyone have a recommendation for a high resolution encoder for use in eurorack modules?
Reporting back on encoders.
I got the Bourns encoder mentioned by @pathein and @barnaby. It’s a nice and compact with a smooth turn, but requiring a much higher force than I would like.
I also got an Alps encoder (which allegedly is used in the MkII Elektron units). The turn isn’t as perfectly smooth as the Bourns encoder, but much lower force is required. The added advantage is that it’s a endless potentiometer, so one can read absolute position.
I haven’t wired them up to compare the ‘feel’ of the resolution. The Alps encoder is significantly cheaper, so I’m hoping it does the job.
Did you end up comparing these?
Been eyeballing some encoders to make a DIY high-resolution encoder (sans LEDs for now).
Hi Rodrigo, the comparison is above.
I meant more on this point really.
I didn’t bother wiring up the Bourns encoder, since I wasn’t happy with the turning force.
With the Alps part, I don’t have the datasheet in front of me, but the precision is excellent. I am reading it in 10-bit, and it registers the smallest movement I can make. Some resting positions produce a small amount of jitter which needs to be compensated for.
I’ve been using interrupt-based reading of quadrature encoders to keep the feel responsive. The advantage of a pot like the Alps part is that you don’t need to worry about missing signals. Thus interrupts aren’t as critical and in turn, you can use microcontrollers that aren’t so well-endowed on the interrupt pin front.
Thanks for the detailed response.
So are you using interrupts at all with the Alps, or just taking a straight ADC (10-bit) reading of the position and that’s it?
And are you using this as just a standalone controller?
I’m thinking of making something that houses 3-4 of these along the curve of my snare, along with a few other controllers I now have hanging around there:
At first I thought about mounting my arc there, but the arc4 is too big/straight, and my (original) arc2 is a bit too heavy/deep to mount effectively.
I looked at @TheSlowGrowth’s arc clone, hoping to have a slightly smaller footprint faux-arc that I could use this way, but it doesn’t look like it would be easily adaptable to that purpose.