SLVU681 Datasheet, PDF (8/21 Pages) Texas Instruments – DRV8818EVM Evaluation Module

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3.3.4 Motion Control
Constant Speed Mode:
• Starting Speed (PPS): The following discussion defines pulses-per-second or PPS. A pulse is a single
step in the logic table. This is not necessarily a mechanical step. If you change micro-stepping modes,
you must double this for the same speed (in 1/2 step), x4 for 1/4 step, and so on.
• Desired Speed (PPS): This is the final speed that the motor ramps to and holds, otherwise known as
the target speed.
• Acceleration Rate (PPSPS): This is how fast the device ramps from the starting speed to the desired
speed. This is also the deceleration rate once you pause stepping.
• Start Steps Button: Press this button to spin. Press it again to stop, or pause, spinning.
• Update Speed Button: While spinning, you can change the Desired Speed field and nothing will
happen until you click Update Speed.
Indexing Mode:
• # of Steps: In Full Step mode, this is the number of mechanical steps you want to take. For example,
if the motor on your bench has 200 steps in a revolution and you want to move one revolution, you
choose 200 steps. If you are in 1/2 step mode, you need to double this to 400 for a full revolution.
• Steps To Stop: When the number of steps taken achieves this point, the motor starts to decelerate at
the rate given in the Acceleration Rate field.
• Stopping Speed: After the steps in the Steps To Stop field is reached and the motor begins to
decelerate, the motor rotates at this speed (once it is reached) until the value in the # of Steps is
reached.
• Move Steps Button: Click this to begin indexing. Once indexing is complete, you can click it again to
repeat the cycle.
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DRV8818EVM Evaluation Module
Copyright © 2012, Texas Instruments Incorporated
SLVU681 – February 2012
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