Stepper FAQ

A. No, if you need to run two stepper motors at once, you need to have two stepper cards, regardless of how many axes it has. Our 3-axis cards can control 3 stepper motors, but only one at a time. The number of motors you want running at once corresponds with the number of stepper cards you need.

Q. In the manual, there are formulas to calculate the velocity resolution, as well as the base and running velocities. These formulas use %AQ3, %AQ4 and %AQ5 which are labeled "Velocity Resolution", "Base Velocity" and "Running Velocity", respectively. How is it that to calculate the Running Velocity, you must take the Running Velocity multiplied by something else?

A. The labels in the manual for the registers %AQ3, %AQ4 and %AQ5 are slightly misleading. The values you plug into those registers are used to calculate the actual velocities according to the formulas.

Q. I used the Stepper Calculator program to find the actual times of moves. I plugged in a value of 500 ms as the acceleration and deceleration times, but the Calculator gave me back actual acceleration and deceleration values that were much lower than what I put in. What gives?

A. The actual acceleration and deceleration times will be shorter than what you put in, because you execute a very short move and the acceleration time is longer than what it takes to get halfway through the move. This means you will still be accelerating halfway through the move, so the motor is going to have to stop. Therefore, it will cut the acceleration short and start the deceleration. The Calculator program takes this all into account.

Q. I’ve set everything up and I can’t get the motor to jog or move or anything. What do I do?

A. The stepper card will not work unless you have an E-Stop button set up, whether you have an actual E-Stop button connected (normally closed) or just a straight short across terminals 19 and 20. When you first power up the module, there will be at least one error in the %I registers, the Power up/Watchdog error %I8. All faults must be cleared before anything will work. Toggling % Q14 can clear the faults. Also, if you are trying to make an absolute move, you must first make the current position valid by setting %Q13 to a 1. When you use the jog function, a 1 in either %Q6 or %Q7 means the motor is on, a 0 means it is off.

Q. The manual says to connect this switch between this terminal and ground. There are two ground terminals on the card, pins 1 and 20. Which one do I use?

A: It does not matter if you do not have an isolated stepper card, pins 1 and 20 are the same. On isolated cards, the Home, High Limit, Low Limit, and E-Stop switches will use the Isolated ground, pin 20. The encoder and all the other inputs or outputs will be in reference to the digital ground, pin 1.

Q. I have the card set up and the stop, acceleration/deceleration and the run lights work accordingly, but the motor is not moving.

A. You at least have the card configured correctly and the E-Stop switch connected right. Now, check all your other wiring to the motor to see if it is correct.