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1063_0_Product_Manual - October 27, 2010 2:54 PM
Choosing a power supply voltage
The 1063 can operate from 9 to 30 VDC. It is able to reduce the voltage if your motor requires less, but it cannot
increase the voltage. First, find the resistance of the coils in your motor. We will assume 4 Ohms. Add 0.5 Ohms
to this to account for the electronics on the 1063. Decide the maximum current you want to push through the coils.
This current limit is per coil, and you set this through the software API when you write your application. We assume
2 Amps. The maximum current for your stepper is part of the motor specification - you can use the stepper with
less current, to reduce power consumption, but you will get reduced torque. Multiply 4.5 Ohms * 2 Amps = 9 Volts.
The minimum voltage you can operate this motor at will be 9 Volts + 0.5 Volts for the controller. If the voltage you
provide is less than what is required for the motor (but still more than 9 volts), the motor will still run, but not at full
spec, and often will be rough when microstepping (<1000 steps / second).
Figuring out your wattage / power supply current requirements
The maximum power is when one coil is being driven at 100%. Calculate power = (2 Amps)^2 * 4.5 Ohms = 18
Watts. It’s good practice to not run your power supplies at 100% capacity, so budget at least 18 watts * 125%
= 23 watts for this setup. You can calculate the current requirement of your power supply by Current = Required
Watts / Power Supply Voltage. We assume a 24 VDC power supply, so 23/24 = 0.96 Amps. Your power supply
should be able to provide at least 0.96 Amps.
API Variables used to control your motor
To use a stepper motor, first select (in software) which motor the PhidgetStepperBipolar should affect. Step
position, maximum velocity, acceleration ramping, and torque/current can be controlled for each motor in both
directions:
Step position is controlled in a graduating scale dependant upon the speed of the motor
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Up to 1016 1/16th steps/second, shaft angle is affected in 1/16th step increments
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1024 1/16th steps/second and higher, shaft angle is affected in full step increments
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The position property always contains a count of 1/16th steps
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Maximum velocity is controlled in 1/16th steps/second up to 32768 1/16th steps/second
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Acceleration/deceleration is controlled in 1/16th steps/second
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up to 1020000 1/16th steps/second
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Current limit is varied between 0 and ~2.5A and is directly proportional to the maximum current through
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the motor up to 2.5 Amps
Effects of Current Limit
The 1063 allows the current applied to the motor to be programmatically set. This is important - if the current
limit is set too high, the motor’s internal resistance will cause the sine-wave approximations used to implement
microstepping to clip at the maximum current possible, given your motor/supply voltage. This clipping will cause
rough operation, or prevent the motor from turning. If the limit is set too low, the motor may not be able to handle
it’s load, by missing steps, or not turning at all at high accelerations.
How to determine CurrentLimit
Disconnect one coil from the Phidget and make sure your power supply is set at the voltage you will use in your
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application.
The CurrentLimit has to be less than the current limit of your motor, so start CurrentLimit at a small value.
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Using our example, change the position until you find a maximum current.
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Move up the current limit until the current feedback is not increasing.
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This is your current limit. If you do not need so much torque, you can reduce the current limit to save power and
reduce heating.
Continuous Rotation
A stepper motor can be caused to rotate continuously by simply setting the motor position property to an extremely
large number of steps. The valid range of values for the motor position property is large enough to be able to cause
the motor to continuously turn at maximum velocity for 194 days.