[Greg Needel]

I agree with what Ty said, you don't need to limit your current for this setup. Those numbers you are getting in the spreadsheet are fully loaded current, a situation that you should never be in since the portcullis is much less than 90lbs (even if you had horrible mechanical advantage I see it never reaching that kind of load).



Now that we have established that you don't need to limit your current, if you wanted to do so anyway, you could do it by limiting the PWM value you send your SPARK.

When you send a SPARK (or any other motor controller) a value of 1 (full forward) you have full power. If you send it less than that you have effectively limited your current via lowering your available power. Assuming your motor had a perfectly linear power curve (which they don't) if you gave a 50% PWM signal you could have 50% power, which would also be less maximum current. There is a chance you get into trouble with this method as you may fall on a bad spot in the power curve, and the fact that motors are not exactly linear so you might have to play with the value you send the controller.