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Thread: controlling external LED arrays with Procyon

  1. #11

    Default Re: controlling external LED arrays with Procyon

    Oops--

    I may have offended. AD, I'm not sure how to interpret your comment. It wasn't my intent to put anyone down or be mean, and I am very sorry if something I said hit the wrong chord. I may have misread something?

    --Scott

  2. #12
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    Default Re: controlling external LED arrays with Procyon

    I don't think you offended him. He's just looking for someone to build the apparatus he wants as he's not skilled with electronics.

    At least that's what I think he means... I'm sure he'll clarify.

    -Ansy

  3. #13

    Default Re: controlling external LED arrays with Procyon

    Andy, et al.

    I just contacted Janice to order two of the Procyon lightframe adapters and wanted to clarify one issue regarding the output of the Procyon.

    To control the current through each LED, I'm making an assumption that the Procyon uses Pulse-Width Modulation of the full 3V/18 mA (whatever it is) drive signal in order to control the "average" current through each LED. This is opposed to using a digitally-controlled current source output for each channel.

    If PWM is used, then I'm guessing that any external control circuitry should be fast enough to keep up with the switching rate and control the external brightness proportionally. Perhaps a simple interface would be to pass the Procyon output into an RC averaging filter and then run that into the DAC input of a microcontroller for further use--for example, to adjust color balance between channels for large color-wash effects or to mitigate the different power/thermal requirements of the large output arrays.

    Thanks,
    --Scott

  4. #14
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    Default Re: controlling external LED arrays with Procyon

    My inclination would be to use an opto-isolator on each channel to protect the Procyon from any misadventure and just use FET drivers (or even bipolar high speed switching transistors) to provide the required drive current. A pot to adjust the FET drive should provide ample colour balance tuning. The PWM output of the Procyon shouldn't need any further conditioning. Obviously a seperate power supply will be required on the LED array side of the opto-isolators.

    Cheers,
    Craig

  5. #15

    Default Re: controlling external LED arrays with Procyon

    Craig, thanks for the info. I think the optoisolator approach is the best way to go, so that's what I'll implement.

    I have a number of solid-state relays, but I don't think they're quite fast enough. I'll have to review the specs. Also, the ones I have on-hand have zero-cross detectors in them, so I don't know how that would affect the overall timing/control if I used a 60 Hz AC line.

    I'll likely stick to DC only.

    Best,

    --Scott

  6. #16
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    Default Re: controlling external LED arrays with Procyon

    Good choice! I suspect solid state relays are a bit overkill anyway. I don't know what sort of current you're after, but I'm very fond of ULN2801 octal darlington driver chips - cheap and convenient.

    Cheers,
    Craig

  7. #17

    Default Re: controlling external LED arrays with Procyon

    Hi--Just a quick update before I have to get to my homework

    My current plans to interface to the Procyon are as follows:

    OPTION #1
    ========
    1. Use a high-speed optocoupler
    2. Create an output voltage proportional to PWM input
    3. Scale voltage and trim as necessary
    4. Pass analog signal into RCD-24 LED driver

    OPTION #2
    ========
    1. Use a high-speed optocoupler
    2. Scale PWM
    3. Drive PWM input of RCD-24 LED driver directly with isolated PWM
    4. Provide analog dimming/current control as necessary to adjust levels

    I'm still unclear as to the exact LED arrays I'm going to use. The Titan looks great but may be way too much for my needs. Any ideas on cheap low-ish power LED spots/linear washes to hide behind a speaker array?

    Here's a picture:


    Thanks again,
    --Scott

  8. #18

    Default Re: controlling external LED arrays with Procyon

    I just placed and order for six RCD-24-0.5 LED constant-current drivers and two HL16-RGB light engines. The light engines fit in a standard MR16 fixture, which is ideal for my situation.

    I will design and build an interface to the LED drivers and spotlight outputs that will allow me to control via the Procyon, DMX, color organ, sound, etc. This will likely have a microcontroller, 16x2 character display for info/programming, etc.

    To get started, though, I'm going to just have a prototype with the RCD-24's and some terminal blocks to output to the RGB lights.

    The HL16's were available from Newark for $53+ each and I got the RCD-24's from Allied Electronics for about $16/ea.

    I still plan to use optoisolators and vactrols (for analog voltages) for the real-world interfacing.

    I'm hoping for results mid-December.

    BTW, the overall goal of this project was so that I could "open" my eyes and get a better color representation with the light reflected off a white surface (so I don't blind myself). With my eyes closed, I mostly see red colors with the Procyon and I would like to better enjoy some yellows/blues/greens.

    --Scott

  9. #19
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    Default Re: controlling external LED arrays with Procyon

    Very cool!

    Keep us updated on the progress. This is a very interesting project.

    -Andy.

  10. #20

    Lightbulb Circuit board coming for Procyon interface

    [edit: PCB artwork is here! Jump a couple of posts down for the .zip file]

    Hello forum,

    This is just a quick note to let you know that I'm creating some very general artwork for a PCB that will interface with the Procyon. For reference, this is the most basic switched current source using a linear regulator, so unfortunately it dissipates a bit of wasted heat and power but is the simplest and cheapest.

    Also, when I stopped development of my prior circuitry, I was relying on some misinformation that I found regarding the Procyon's output--ultimately, my problem here lies in not having a schematic and a dead oscilloscope, but I recently purchased a cheap USB 'scope and have verified that the LED outputs seem to be open-collector, which accounts for the "noise" that I noted in a prior post when I used an IR LED (from an optocoupler) as the input load. Because the IR LED was not forward biased when the output of the Procyon was "off" there was an observed noise.

    For those who have made prior circuits, simply place a resistor, say 620 ohms, in parallel across each optocoupler input. I will update the "cheap" schematic and will include these pull-up resistors in the circuit board to come.

    I have created a full circuit board with constant-current DC-DC converters but their PWM frequency is about 200 Hz and it looks like the Procyon is around 26 kHz for its PWM frequency. As a test, I'm writing a quick program in an Arduino microcontroller board (using a Mega right now) that will scale the 26 kHz PWM output of the Procyon to a lower-frequency (but same 8-bit resolution) PWM. It is expected that there will be a one-sample latency between what the Procyon outputs and the modified PWM output to the external high-powered LED driver--this is necessary because I have to determine the "average" duty cycle over this period.

    Over time, I will make an interface that behaves as quickly as the linear circuit but has some of the power-saving features of a switched-mode power supply.

    I am not charging any money to make these circuits available and will see what the best methods are for posting and answering questions that would otherwise be outside the scope of this forum. If any administrators would like to contact me, please feel free to leave me some ideas so that the members who are interested in this can benefit.

    I still love my Procyon and use it often--especially when I can't sleep because I have too much on my mind. It's quite fun to watch the Procyon sessions with high-power external LEDs being shown on a wall (more of a color organ feature, I suppose).

    Thanks for your patience,
    --Scott Thompson
    Last edited by electronguy; 02-13-2011 at 06:58 AM. Reason: Project complete. See bottom post for PCB artwork.

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