Q about optical sensor leads

Home Forums Altura Theremin MIDI Controller Forum Altura FAQ & Support Q about optical sensor leads

  • This topic has 42 replies, 3 voices, and was last updated 2 years ago by Coffeepal.
Viewing 15 posts - 1 through 15 (of 43 total)
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  • #31443 Reply
    Coffeepal
    Participant

    Just wanted to say I’m very impressed by its performance now that I’ve gotten it together. I’m using it with a NTS-1 right now, it’s dreamy.

    Question: are these cables going to the optical sensors highly sensitive or delicate? And could I replace them with something longer? Maybe using CAT5 cable?

    #31445 Reply
    brach
    Moderator

    Coffeepal,
    I’m glad you are enjoying your Altura.
    Not that it probably matters, but the sensors aren’t actually optical, they are ultrasonic…which is a much different technology and may be a factor in how you end up using the Altura.
    But to answer your question, there is nothing special about the ribbon cable that connects the sensors. You could use cat 5. Whatever you use, my suggestion is to not solder directly to the headers of the sensors. Instead, cut one of the ribbon cables in two and strip the 4 wires and solder the cat 5 wires to those. That way you have a female header that you plug directly onto the sensor male header. It keeps things more modular that way and easier to troubleshoot or replace things.
    One factor you need to be aware of is that the Altura has no driver for the sensor signals, so there is a finite limit of how long the cables can be. The distance depends on the capacitance and resistance of the type of cable you are using and the drive capability of the microcontroller and sensor hardware. If you want to make it much longer than what it currently is, you’ll just need to experiment with what works for you. I imagine that a couple of feet of cat 5 will probably be fine, and cat 6 would even be better.
    Good luck.
    -Brach

    #31450 Reply
    Coffeepal
    Guest

    Hey thanks, Brach. I mostly was interested in the possibility of trying the sensors in different configurations. This thing is so awesome!

    #31451 Reply
    brach
    Moderator

    Great! I’m really glad you like it!

    #31452 Reply
    Coffeepal
    Guest

    Here’s one that just came up. Somebody mentioned maybe turning the sensors more facing each other, so their fields crossed, I assume. Does anybody know why this isn’t done? Seems to me having sort of a virtual joystick, which could even be, say, the bell of my horn? They always do it with two sensors and two hands apart, and it seems kind of intuitive to do it with one moving point instead of 2. Don’t know how practical that is, which is why I’m asking you. Would they interfere with each other? All kinds of questions come to mind. But historically Theremin players have always used two hands separately and I just wondered why. Any ideas, pls let me know.

    #31453 Reply
    brach
    Moderator

    I suppose your talking about making the sensors pickup in some sort of Cartesian coordinate pickup pattern…like the Kaoss pad uses the X-Y planes. Unfortunately, in the Altura’s case you can’t really cross the sensors because they will interact with each other, based on what i was saying earlier about the sensors being ultrasonic technology rather than optical.
    Historically, 2 hands were used with Theremins because controlling pitch and volume need to be independent of each other. I don’t think it would be too easy to try it with one hand. Besides the circuitry would have been very difficult to design with the analog components they had 90 years ago when the Theremin was invented.
    -Brach

    #31455 Reply
    Coffeepal
    Guest

    Thank you so much! Here’s another: a buddy online told me I should probably be able to use a better sensor in place of yours with little or no modifications, just drop it in more or less. time-of-flight sensors, specifically VL53L0X/VL531X is the phrase he used. You have any thoughts on that?

    #31458 Reply
    brach
    Moderator

    Unfortunately, your friend is wrong about it being a drop in replacement. The hardware is rather different (once again ultrasonic vs. optical), which means that the sensor uses different types of pins with completely different data coming from them. Of course anything is possible if you want to put enough resources into it, so you could re-write the software to make it work. But the VL53L0X isn’t really an upgrade to the SR04. When I was designing the Altura I specifically used the ultrasonic sensor because it worked much better in this application. Here’s a video pointing out what I discovered…. https://www.youtube.com/watch?v=gGtD93wb7xI
    The thing the optical sensor is much better at is detecting distance of angled objects, which isn’t necessary in the Altura’s application. What I wanted was accuracy, which the SR04 is much better at. Another factor is stability; and if anyone is trying to use an optical sensor on a stage with unpredictable stage lights, that could be a problem. There is a lot of light pollution in the IR range in those types of environments.
    Anyway, that’s my thoughts.
    -Brach

    #31461 Reply
    Coffeepal
    Guest

    Hey wow, I’m honored to be talking to the guy that made this baby, eh? Well thanks, it’s just what I wanted. I hope you have some more. I’m going to buy another one and take all those little pots and run them to a breakout box that sits on the ground and you control it with your feet. How do you like that? I should be able to do it with a 15-pin D-Sub cable or a printer cable, right?

    #31462 Reply
    Coffeepal
    Guest

    I mean each pot has 2 wires and a ground, which only needs to be one wire for all 7, right? So 14 wires for the pots, one common ground, I can do that with a serial cable or like 3 CAT5 cables, if I’m thinking correctly here. I’m not terribly good at electronics, but I try to make it up in enthusiasm. 🙂

    #31463 Reply
    brach
    Moderator

    You certainly are enthusiastic!
    Each pot has 3 pins: ground on one side, +5V on the other, and the wiper (center) which gives out a voltage between 5V and ground depending on how far it’s turned. So if you want to put all the pots in one box, you’d just need one wire for each pot’s wiper plus a 5V wire and ground wire (which can be run in series to all the pots)…that’s 9 wires in total. So a something like a VGA cable could work, if you want to use D-sub connectors.
    Look at the schematic in the back of the assembly manual to see how the pots are wired.
    -Brach

    #31464 Reply
    Coffeepal
    Guest

    Okay cool. But this isn’t happening until I make a little scratch to buy another. I want to leave my first one in its original condition. I’m working on several simple gadgets just for fun, really excited to find your Altura, combining a nice arp and a Theremin controller makes for a really amazing experience, esp. after I additionally put on the reverb, delay and phaser. This is soooooooooooo mmuch better than just a Theremin.

    #31465 Reply
    Coffeepal
    Guest

    Hi, a friend is asking to see the source code. He appears pretty convinced he can modify the source to trade out the sensors that come with the kit with a different set and that doing so may provide some kind of value. I think me and Brach discussed this in the other thread. At any rate, he’s asking for the code and I may be interested in trying different sensors just for fun — though I’ve told you I have other things in mind myself, things more simple and tactile. But I’ve had two buddies at my electronics forum suggest trying it, I dunno.

    Can you tell me where I may find the source?

    #31466 Reply
    Coffeepal
    Guest

    I guess I should be more specific. A friend has asked if there is firmware that he can see.

    #31467 Reply
    brach
    Moderator

    Like I said, anything is possible if you want to devote enough resources to it.
    Check out the software section under the documentation tab on the Altura page.
    Good luck!
    -Brach

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