Spikemark Tip: Turntable positioning

December 6, 2011

We often get questions from people who are having a hard time getting their turntable to hit a position, so we want to go over the quickest way of positioning a turntable and maybe clear up some of the confusion.

Every machine has an encoder that sends information to Spikemark as counts. In Spikemark, the user can choose to cue that piece of scenery using those counts, or translate them into inches, feet or degrees using a position scale. Inches and feet are great for linear movement, but for a turntable, the best way to represent the encoder counts is by having Spikemark translate them into degrees. Let’s look at how we do that.

Once you’ve connected the turntable machine to Spikemark, take a look at the Positioning Window in the Motor Editing Pane. Make sure that the Position Units is ‘counts’, Position Scale is set to ‘1’, and then reset the Position to ‘0’.

On the turntable, make a physical mark that lines up with a fixed mark on the stage. Then, using the manual control, move the turntable four complete turns until the mark once again lines up with the fixed mark. Note: You can rotate any number of complete turns- the more turns, the more accurate your result.

Next look at the motor in the cue grid and you will see a big number followed by ‘cts’.

That’s the number of counts that the encoder sent to Spikemark during four full revolutions of your turntable. Now we need to determine a position scale with a little math. Let’s say you moved 2,983,996.8 counts in 1440 degrees (360 degrees * 4 turns). 2,983,996.8 / 1440 = 2072.22. That’s your position scale. Go back to the Position Window of the Motor Editing Pane, enter your position scale and change the Units to ‘Degrees’.

Now you’re done. If you want to move the turntable one full revolution, just set the target to 360 degrees more (or less) than where it currently is. Half a revolution is 180 degrees, 720 degrees will revolve the turntable twice, etc…

That’s it for the December Spikemark Tip of the Month. If you have an idea for something that you think could use a little explaining just leave us a comment or send me an email at ian@creativeconners.com.

Spikemark Tip of the Week

By Peter on

November 24, 2011

- Automation, Spikemark

A common question we get here at Creative Conners is how to build a multi-step cue. We will look at two possible scenarios and explain how to achieve the effect using Spikemark. The first scenario: A turntable rotates slowly at one speed and then at a certain point, without stopping, the speed changes and the turntable continues at the new speed until the cue ends. This is actually pretty simple to pull off. The trick is to write two cues that overlap, and when the second cue starts, it will smoothly take control of the turntable. Let’s take it step by step. Cue #1 rotates the turntable at 1 revolution per minute with a target of 720 degrees. The second cue rotates the turntable at 2 revolutions per minute and also has a target of 720 degrees. Cue #2 is linked to Cue #1 with a position trigger, so that when the turntable hits 360 degrees Cue #2 will start. When cue #1 runs, as soon as the turntable hits 360 degrees cue #2 takes over, speeds up the revolve, and completes the cue. Cue #1 never completes since it is superseded by cue #2, but that’s OK, Spikemark simply moves on to the next cue. Our second scenario: A wagon tracks upstage towards a wall and when it gets near the wall, the wall bi-parts, allowing the wagon to travel through. The problem with this scenario is that you don’t want the wagon to crash into the wall panels, and you don’t want the walls to open until absolutely necessary so that the movement looks slick. The solution here is three cues. Cue #1 has a target that stops the wagon before it gets to the wall (in case the wall does not open). Cue #2 opens the wall, and can be driven with a position link to of cue #1. Cue #3 moves the wagon through the wall and can be triggered with a position link that references the wall opening once the gap is wide enough for the wagon to get through. The trick is that cue #3 is triggered from cue #2 before cue #1 finishes, so it looks like the wagon has one fluid motion towards it’s upstage target. If something goes wrong, and the walls don’t open, the trigger point for cue #3 is never reached and cue #1 stops the wagon short of a collision. Pretty neat, right? By the way, multi-speed cueing is explained in the Spikemark manual on Page 103. That chapter has a lot of info about complex cue creation and I urge everyone to check it out.