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Thread: Using Arduino to read DMX for Maestro Servo Control

  1. #31
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    Default Re: Using Arduino to read DMX for Maestro Servo Control

    Wow, thanks​ so much for this! I will modify the timeline so it looks exactly the same and get back to you later.

    Sent from my Moto G (4) using Tapatalk

  2. #32
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    Default Re: Using Arduino to read DMX for Maestro Servo Control

    Hi Barnabybear, thank you again for the excel doc; it was very helpful. I set up my timeline in Vixen so that it would exactly match your example, and made a new custom value effect for each cell. For the speed change frames, I kept the effects at 0.5 second intervals; however, for the position change frames, I varied their lengths. Despite these adjustments, it still seems that my servo controller is treating each frame as a new position command. Instead of changing the speed, the speed changing frames only move the servo. To make sure that I set everything up correctly, I attached some screenshots of the first two columns. Unfortunately, from what I can tell, Vixen doesn't make it easy to see an effect that doesn't have a color association. If you would like a different image or more information, please let me know. Thank you so much for helping me work through this!
    1.jpg2.jpg3.jpg4.jpg5.jpg

  3. #33
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    Default Re: Using Arduino to read DMX for Maestro Servo Control

    Here are the remaining images:
    6.jpg7.jpg8.jpg

  4. #34
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    Default Re: Using Arduino to read DMX for Maestro Servo Control

    Hi, the set up is spot on. It looks like it's my bad Try changing the 207's in the 1st channel to 135. You should only need to do this in two places.

    In the data sheet it gave the value as 0x87 which is a hexadecimal value. I converted it using the programmer calculator on my PC and looked at octal (207) not decimal (135).

  5. #35
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    Default Re: Using Arduino to read DMX for Maestro Servo Control

    Hello, thank you for the updated info. After changing the 207's to 135, there's good news and bad news. The good news is that the servo no longer moves when processing a speed change command, so you're definately on the right track. The bad news is that the speed doesn't change. In fact, throughout the entire sequence, the servo moves rather quickly; and it doesn't make any difference if I set the speed to 1 or 130 (I even tried 150 for kicks). Could this be related to the hexadecimal issue? Thanks so much again!

  6. #36
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    Default Re: Using Arduino to read DMX for Maestro Servo Control

    Hi, looking at this now - it's been a busy weekend.

  7. #37
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    Default Re: Using Arduino to read DMX for Maestro Servo Control

    Hi, this is taken from the polou website but I'm not sure it's all of the problem.

    Why do servo speed and acceleration limits not work for the first movement after startup or after setting the target to zero?

    When the Maestro first starts up, the servos could be in any position, and the Maestro has no way of determining what position they are in. The standard RC servo protocol provides no way to get feedback from a servo. Therefore, when the Maestro receives its first Set Target command for a servo, whether it comes from serial, USB or an internal script, it will not be able to produce a smooth transition from the current position to the target position and will instead command the servo to immediately go to the target position. The speed and acceleration limits will work for subsequent commands since the Maestro will know where the servo should be and can produce servo pulses that smoothly change from the current position to the target position.

    If you need your servo’s first movement to be controlled by the speed and acceleration limits, then the first Set Target command you send to the Maestro should correspond to the servo’s current position. For example, if you know that your servo will always be at a position of 1500 μs when your system starts up, then your first Set Target command for that servo should have a value of 1500 μs.

    Similarly, if you set the target of a servo to zero to make the Maestro stop sending pulses, the Maestro will lose its knowledge of where the servo is. During this time, the servo might slip and go to a different position. If you know your servo is not going to slip, then your program or internal script could remember where the servo is and send a Set Target command with that position in it before trying to move the servo to another position.
    One other thing to try. On the speed seting column, set the 'set position' to 50 and 'speed' to 0. That should be realy slow. If it works you can leave the speed value as zero and just change the speed with the set position but you can't delete that row.
    Last edited by Barnabybear; 05-11-2017 at 02:25 PM.

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  9. #38
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    Default Re: Using Arduino to read DMX for Maestro Servo Control

    Hi Barnabybear, sorry it has taken me a while to get to this, but I finally had the time to test out your suggestion. IT WORKS! Thank you so, so much for all your help! By changing the start and set positions, I was able to adjust the speed and movement of a servo in Vixen. I really appreciate all the time that you put into solving my problem and really can't thank you enough!

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