• Hi there!

    @GreaterThatZero: Totally agree! And another point: How to map led output from applications that was designed for arcs to this single rgb-led? No way IMHO!
    Anyway: One (or more) of these would make a nice MIDI-CC device. Imagine morphing through different synth-sound parameters with it's two directions - could be fun and intuitive.

    About my progress:
    I'm still lacking the correct sizes. If you own an arc (2 or 4 - doesn't matter), please take some minutes to measure these sizes:
    1. diameter of the knobs
    2. height of the knobs (from the glass surface to the top would be great)
    3. diameter of the glass ring
    4. width, height and depth of the wooden case
    5. width and height of the aluminium faceplate
    6. space between two wheels (glass ring to glass ring)
    7. space between faceplate border and wheels (border to glass ring)

    Thanks a lot, that would be great!

  • any updates?

  • hmm. this looks familiar:

  • So Im getting back into my musical hardware projects this fall/winter as I FINALLY fininshed residency and have some more time at my new job.....Anyway I have some boards I had made awhile back and built 1 of them up and did a quick arudino sketch to test it awhile back. Im not really planning on taking it much further but was wondering if anybody would like the boards. Ill post some pics and info in the next few days of what point I left off at. Id like to see somebody help finish this, if possible. Anyway Id be happy to USPS them to ya for the cost of shipping.

    Heres where I left off......
    Here is my attempt. I am currently waiting for the boards and parts to arrive (didn't order the actual encoder yet as it runs about 20 USD!) My design uses 4 TLC5926 current sinking drivers connected to an arduino. The leds are 2mm type with a circular "stalk" so the faceplate can be as basic as a ring of round drill holes, or one could add a clear acrylic ring on top of that coupled with an aluminum faceplate to achieve a more Arc like aesthetic. The biggest hurdle at this point is coding so only 1/4 of the leds are actually on at one time as constantly driving all 64 at 10-20ma would require an external power source.

  • Pics of the board. I have to find out what the pinnouts are on the header...

  • looks great!!!

  • great work!

  • @shimoda Yeah whisper me your shipping info and Ill send a couple...Pretty easy assembly as everything is thru hole save the 4 chips.....
    It lives!! (UPSIDE DOWN SORRY!)
    Well this is just a sketch made for 4 8 bit shift registers so its just doubling the pattern on each IC but it demonstrates (I think) that the SPI communication is working and the electronics function appropriately.
    I used this information and sketch
    Here are the Eagle files and gerbers and the pinouts:,h49q9w16njp64t5

    So I need some major programming HELP Id eventually like to get this packaged up with a teensy and have it plug and play midi. So I guess the next step is trying to address/select the leds with an attached encoder......

  • Yes, the LED drivers are current sinking so their 16 "out put" pins connect to the cathode of the LEDs.

  • The EM14 label refers to a Boruns encoder. I used the PCB layout for the axial mounted but have yet to actually order one. I specifically had the EM14C0B-C24L064S Look at the data sheets as many of the attributes can be changed including getting a cable if you are not board mounting as the hole in the center allows mounting the encoder from underneath.

  • Just curious if there might be a way to get my hands on one or two of these boards...? Also curious if you've made any further progress with the project

  • Ok so Ive slowed development on my end on this as I have some other more pressing projects I willing to send out some boards and help with the hardware side but Im currently not willing to further my ardunio/programming knowledge. At this point I got some help with a sketch to address the LEDs with various patterns but have yet to progress beyond that. Im willing to mail some boards so whisper me your mailing info and Ill send a couple out to you. Ill make sure to check this thread regularly from this point on.

  • I've been working on this off and on as well and here's what I have so far.

  • Woah, that's neat! @chankster, have you got any schematic/pcb drawings yet? ^_^

  • Wow. Well done.

  • @artfwo, I'll try to get the LED board eagle files posted up tonight. The top board uses 4 TLC5940s to handle the led addressing and then plugs into a pcb that holds the micro and encoder. Unfortunately I accidentally flipped the encoder footprint the wrong direction so I'll need to fix and get new bottom boards made.

    Schematic -
    Board -

  • Eagle files for the LED ring.

  • What about the control board you are using chankster? I assume those are the bottom boards you speak of...

    @bobsagat, I haven't had a chance to do anything with those boards, but finally got the smd chips to populate one, just going to have to figure out interfacing.

  • @shimoda, correct. I need to flip the encoder footprint first and test out a few things before I'd feel comfortable posting it.

    Also, like bobsagat666, coding is not my strong suit.

  • Hello Monome Community,

    some moths ago, i posted, that i will be working on an arc, too. I did not have much time until now, but finally i managed to put some work into my diy arc.

    My first approach was a test board to check how well dimming would work with 8 shift registers 74HC595. This is what looks to be the way the original arc works. Some calculations showed, that dimming would be possible at a speed of about 100Hz, which is not quite much. Actually it would appear flicker free to the human eye, but would still flicker on cameras.
    The test board runs fine now, I have a video that i will post soon. For 16 levels of gamma corrected brightness it requires at least 128 steps for one PWM cycle. For each step, 8 bytes have to be pushed out to the shift registers.
    The software is written in C right now and is really busy shifting bytes out and calculating the next cycles. The problem here is that the compiler does not perform well in interrupt service routines. Actually it saves lots of data when jumping into an ISR and restores the data when jumping out. This makes ISRs generally a lot slower. Now that ISRs are happening every few u-seconds or so, the processor is spending lots of time jumping in and out of ISRs.
    I carefully studied the assembly code that the compiler generates and it seems the software could be a bit faster when it would be written in native assembly language.
    But still, it is unclear, if the processor will be able to read data from the encoder and respond to incoming data from the computer, when it is 90% busy updating the leds.
    Overall, I'm not happy with this approach.

    So i eventually decided to discard this and go for a different approach.
    It seems everyone is using TLC5940 chips here, 4 per wheel. These are generally harder to get and quite expensive at times. I have some new approach using only one TLC5940 per wheel. New PCBs are already designed and will will arrive soon.

    I will check back and report my progress soon.


  • I hope your project uses the DIP 5940s (not sure if they come another way) as I have enough for at least two knobs, maybe three. I think I have 12 on hand at the moment. Interested in chanksters and still need to populate the ones bob sent but alas coding will be my weaker suit (more like a t-shirt and shorts for me). Now if only the protocols could be done in max (not the apps) I might stand a chance.

  • @shimoda:

    The TLC5940 comes in many different shapes, just take a look into the data sheet.
    I use the SMD version (got some samples from TI) because it makes layout work much easier (it does not affect the back of the pcb). Generally, if you want to get close to the dimensions of the real arc, its pretty much impossible to use non-SMD parts.
    I might make through-hole versions of my boards as well, if enough people are interested. But these will definitely be larger that the real arc!

    I can't understand why people are afraid of SMD soldering - sometimes its even simpler than through-hole soldering. You just need a good iron (mine is ~30€) and some decent flux. I made many SMD boards so far and even self made boards without the solder-stop-lacquer are no big issue.


    PS: Just updated my case design so the new boards fit. I'll check back later to post some images.

  • Unfortunately the 5940s I have are DIP, not smd. I have soldered some smd stuff without problem. Funny enough, doing a chip has been easier than aligning resistors and capacitors! If you get the board working for DIp, despite if it was bigger I would be game.

  • Hello community!

    I just wanted to note, that I took some time to write down my progress:

    There are some renders of the boards i ordered and a little video as well. I just finished writing, so it might be full of spelling errors and grammar rubbish, sorry for that. You can drop me a line, if you found some nonsense.

    Oh, and the layout of my homepage has gone crazy, too.

  • Hi Vurma,

    yes, I am working on a case design (I made CAD files for a good design), but so far I have no idea, how it could be manufactured.

    Things like the knobs should be relatively easy to make with access to a lathe.
    The light shapers could be laser-cut from pvc or something similar. Here in Gernamy lots of key-service-shops (don't know, if that's the right word for it) have tools for engraving. These can often cut pvc, too. I have not contacted any shop yet, though.
    The wooden case can be made at home. I have a router myself, and getting some good piece of wood should be no problem.
    The faceplate makes my head ache... I have not used a manual milling machine yet and I fear that drilling circles with it is complicated. You might need a CNC milling machine for the faceplate.
    Schaeffer AG does faceplates here in Germany (I think they ship to the US as well) but their price will be in the range of 140€ for just one faceplate. This is pretty expensive imho.

    This is what I thought about so far. To be honest: I want the electronics to work, before I start thinking about manufacturing the case. I just made the CAD files to define the dimensions of the boards as well as the holes for mounting.

    Sounds like your working on one, too. What is your plan?


  • At a cursory glance, I'm not really sure what this is based on, but I tripped over this video a couple of days ago..

  • Without making promises - I can work on one, im fortunate that my university has all sorts of wood/metal work machines (im 90% they have a lathe). We also have a laser cutter.

  • Hello to you all!

    This video has been posted by me. :) As I wrote earlier in this thread, it was a first attempt for a very cheap solution which did not work as good as I hoped it would. I have a different approach now, see the link in the video description.

    @Vurma + dean:
    Thanks for your offer! We'll see what happens, once the electronics are finished.

    Regarding the lathe+metal work machines: My university has several well equiped workshops, too. But afaik it's difficult to get them make something for you (or even assist you with it), because they are usually busy working on more important stuff than some students private projects...

  • Salute,

    check your mails B

  • Hello again,

    unfortunately the recent changes in the monome forums screwed up my user name (no german letters allowed anymore). I took this chance to get rid of this stupid name and created a new account. You can be sure it's still me (Bääääär) :)

    When clicking through the new website, I noticed new images of a dissassembeld arc. I was very happy discovering that the new arc series uses the principle of a TLC5940 as a matrix column driver and some kind of MOSFET for switching the rows. It's actually almost identical to the schematic i postet on my website. Check out those images over here:

    I'm still waiting for the pcbs to arrive...

    TheSlowGrowth formerly knows as Bääääär

  • My uni happily assists us with making whatever as its such an important part of my learning (interaction design).

    Can I ask how many PCB's you have ordered? Id love to get on this ASAP and would buy some from you.

  • This project is turning more awesome by the day.

  • Hello dean,

    I'm happy to hear, your uni assists with the project!

    Regarding the PCBs: I have ordered a set of PCBs for one arc4. It was quite expensive, as it is always, when you order small quantities. Even though I am optimistic, I can't be 100% sure they work fine, until I have a working device. That means, I can't sell you any pcbs right now.

    When the device is in a working condition, I will think about organizing a group buy, if there is enough interest. But this is not a promise - I have not yet checked the legal aspects of exporting stuff like that.

    TheSlowGrowth formerly knows as Bääääär

  • no problem, keep us updated. thanks.

  • Hey community,

    The pcbs and parts have arrived. Assembly of the first prototype is finished and a small firware is up and running.

    The concept works great! Take a look here:

    TheSlowGrowth, formerly knows as Bääääär

  • Does look great, very exciting!

  • Some news:

    Led rings are working beautifully!

    I'm currently working on the communication between the USB-Board and the led ring drivers. The connection is based on I²C and the USB board can already send commands to update the led display of multiple led rings. The transmission-speed actually allows for screen-refresh-rates up to 500times a second. That's pretty good for the un-optimized code and more you'll ever need!
    However, sending data in the other direction (from the rings to the USB board) does currently crash the whole bus. It's weird, but I guess its a programming mistake. I'm working on it.

    I'll keep you updated,

  • Thanks for the update. Your hard work is paying off for sure!

  • Awesome!!

  • great progress so far, looks very promising.

  • Almost done - 90%

    All my sources will be available soon.

  • very exciting. curious, what has this project and parts cost you? Specifically faceplate and ponoko parts.


  • Wow man, great work!

  • This is very exciting news I am hoping to build again...