URGENT MOTION CONTROL PROBLEM;

Projects General Guidance
1

I have a problem with a stop motion dolly, we are doing shots that take 9 hours to achieve 4 seconds of animation, and we have animation software -> arduino - > techzone gen3 stepper motor driver ->nema17(200steps) pushing a camera along a dolly 5 steps after every frame the camera takes

Link to some test footage: (best to step through frames in quicktime using arrow keys)

http://marklagana.com/dollyprob.mov

now we have tried to do a close up pan and it looks like every FOUR frames it moves like 7 steps for some reason?

I tried 4.2 steps every frame, and it worked for 3 and every fourth frame it just didn't move at all. So now we are using whole numbers only and that made every forth frame work, but the dolly has done 4 huge shots already just went to do a close up and we can see every forth frame is moving a bit more?! Please look and offer me any advice...

Could it be i had it set to 200 steps per rev but the techzone driver is half stepping? No documentation on the site no info about microstepping so i assumed FULL steps but now i'm thinking it might be half stepping on me... could this be screwing up every fourth frame??

i'm not animating tomorrow but they are with my dolly, i've told the director in the morning to try setting it to 400 steps... will see how that goes... but this is a huge production.. we have volunteers from all over the world... who i consider best in the world, i really don't want to be the weakest link!!!

here is the link but do not bother looking for microstepping info it is not there nor in the documentation: http://techzonecom.com/detail.php?pr_id=30

here is the script, it is controlled from the software dragon stop motion

#include 

#define STEPS 200

Stepper stepper(STEPS, 1, 2);
byte inbyte = 0;

void setup()
{
  Serial.begin(57600);
  stepper.setSpeed(30);
}

void loop()
{
inbyte = Serial.read();
if (inbyte == 'S') stepper.step(5);
if (inbyte == 'D') stepper.step(-5);

}

more pics on the short film if you're interested: The Maker

2

OH and also after some frames i can HEAR the motor making a different sound...

but stepper speed and stepper steps are the same so i should hear the SAME sound EVERY time correct?

Meaning it can't be mechanical..

3

ok guys i worked this out first of all the card was half stepping, for future reference here is a quote from nophead at the reprap forums,

They need to be half stepping to get 0.1mm resolution with 200 step motors.

4

ok the stepper size going to 400 didn't actually help! It's still stuttering... moving a bit forward every 4 frames any ideas anyone?

5

What if instead of using the stepper class... I used low high commands to the stepper pin?

How many milliseconds would one leave the step pin on a stepper driver HIGH to push 1 step?

6

My only other idea is to cut out the software all together, control the canon DSLR camera through arduino with a mosfet... I guess i will just have to try pity it's 2 hours away from my studio

7

My only other idea is to cut out the software all together, control the canon DSLR camera through arduino with a mosfet... I guess i will just have to try pity it's 2 hours away from my studio

edit: but the arduino is still just sending the same thing over the same wires to the stepper driver, so sending the arduino commands from a computer OR pushbutton wouldn't really make a difference would it? why would it be changing every four frames arghhh i'm going insane here.

8

arghhh i'm going insane here.

Well, they do say talking to yourself is one of the first symptoms.

9

i think i decided to go insane when i became a stop motion animator and then became fully fledged insane when my camera dolly moves slightly further every FOURTH move