1062 User Guide

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Getting Started

Checking the Contents

You should have received: A PhidgetStepper Unipolar 4-Motor A Mini-USB Cable		In order to test your new Phidget you will also need: A 5 to 12V DC Power Supply (If you use the barrel connector, make sure your power supply is center positive polarity. Also ensure that the power supply doesn't exceed your motor's voltage rating.) A stepper motor (5, 6, or 8 wire)

Connecting the Pieces

Connect the motor to the PhidgetStepper board. If you are having difficulty connecting your motor, refer to the Technical Section in this manual. Connect the power supply to the board using the barrel connector. Power supplies with higher current (more than 2.5 Amps) should be wired directly to the terminal block. Connect the PhidgetMotorControl board to your PC using the USB cable.

Testing Using Windows 2000 / XP / Vista / 7

Make sure you have the current version of the Phidget library installed on your PC. If you don't, follow these steps:

1. Go to the Quick Downloads section on the Windows page
2. Download and run the Phidget21 Installer (32-bit, or 64-bit, depending on your system)
3. You should see the icon on the right hand corner of the Task Bar.

Running Phidgets Sample Program

Double clicking on the icon loads the Phidget Control Panel; we will use this program to ensure that your new Phidget works properly.

The source code for the Stepper-full sample program can be found in the quick downloads section on the C# Language Page. If you'd like to see examples in other languages, you can visit our Languages page.

Updating Device Firmware

If an entry in this list is red, it means the firmware for that device is out of date. Double click on the entry to be given the option of updating the firmware. If you choose not to update the firmware, you can still run the example for that device after refusing.

Double Click on the icon to activate the Phidget Control Panel and make sure that the Phidget Unipolar Stepper Controller 4-motor is properly attached to your PC.
Double Click on Phidget Unipolar Stepper Controller 4-motor in the Phidget Control Panel to bring up Stepper-full and check that the box labelled Attached contains the word True. Select the connected motor. If you have connected your motor at the same place as the one in the picture on page 6, it should be motor number 0. Check the Engaged box to power up the motor. Move the Target Position slider to the right or the left. The target motor position will be displayed in the Position Target box and the motor will start turning until the Actual position is the same as the target. Use the Velocity Limit slider to set the maximum velocity. The motor will accelerate until the Actual velocity is equal to the Velocity Limit. Use the Acceleration slider to increase or decrease the acceleration. When the motor has reached the position target, a tick mark will appear in the Stopped box. When the motor is stopped, you can set the current physical position of the motor to a certain value by using the Current Position slider. This is useful for zeroing the motor to a certain physical position.

Testing Using Mac OS X

1. Go to the Quick Downloads section on the Mac OS X page
2. Download and run the Phidget OS X Installer
3. Click on System Preferences >> Phidgets (under Other) to activate the Preference Pane
4. Make sure that the Phidget Unipolar Stepper Controller 4-motor is properly attached.
5. Double Click on Phidget Unipolar Stepper Controller 4-motor in the Phidget Preference Pane to bring up the Stepper-full Sample program. This program will function in a similar way as the Windows version.

Using Linux

For a step-by-step guide on getting Phidgets running on Linux, check the Linux page.

Technical Details

How to Connect your Stepper to the 1062

Unipolar Stepper motors are available in 5, 6 or 8 wire configurations.

5 Wire Stepper Motors

In a 5 wire motor, the center taps of the coils are connected together. This scheme prevents this motor from being controlled as a bipolar motor. To use a 5 wire motor as a unipolar, the center tap wire is connected to the power supply. Determining how to connect a 5 wire stepper to a Unipolar Stepper Controller, like the 1062 can be done by following this procedure. Start by measuring the resistance between all the wires. Below is a sample table of resistance data, in ohms. This table contains example values, your readings may be different but should still produce a similar pattern.

Wire Color	Blue	Green	Red	Yellow	Purple
Blue		147	74	147	147
Green			74	147	147
Red				74	74
Yellow					147
Purple

Looking at the table, you should notice a pattern; the red wire has the same resistance to the other four wires. This tells us that red is our + (center tap) wire, and should be wired to the power supply connection. On the 1062 PhidgetStepper, the power supply connection is labelled as (+). There are two power supply connections available on the 1062 for each motor - either can be used. Disconnect the power from the board and connect the center tap wire to the (+) connection.

Pick one of the remaining four wires and wire it to the A terminal, and connect the other wire for that coil to the B terminal. Connect the remaining wires to C and D. The motor should work regardless of which wire is connected to C and which is in D, but one of these combinations will result in a clockwise rotation for increasing position and counter-clockwise rotation for decreasing position, and the other will produce the opposite rotation.

6 Wire Stepper Motors

The process is similar to a 5 wire motor. On a 6 – wire motor, there will be two + wires, one for each coil, which are the center taps for each coil. You will need to isolate which are the center tap wires and the corresponding wires for their coil. These center taps must be wired together to the power supply. Let’s assume our six wire stepper motor wires are colored as follows: red, green, black, white, brown, and yellow. We measure the resistance between all wires and are presented with the following values in ohms (these are simply example values) :

Wire Color	White	Red	Blue	Green	Purple	Yellow
White		∞	∞	∞	10	10
Red			10	10	∞	∞
Blue				20	∞	∞
Green					∞	∞
Purple						20
Yellow

Looking at our table, we can see our pattern. The white wire has the same resistance to the purple and yellow wires. The red wire has the same resistance to the blue and green wires. White, purple, and yellow bring out one coil, and red, blue, and green are the other coil. The red and white wires are the center of their coils.

Disconnect the power from the board and connect the red and white wires to the (+) terminal block connections on the PhidgetStepper. Pick one of the remaining four wires and wire it to the A terminal, and connect the other wire for that coil to the B terminal. Connect the remaining wires to C and D. The motor should work regardless of which wire is connected to C and which is in D, but one of these combinations will result in a clockwise rotation for increasing position and counter-clockwise rotation for decreasing position, and the other will produce the opposite rotation.

8 Wire Stepper Motors

8 Wire Motors are very difficult to wire up if you do not have a schematic showing how the wires are connected to the internal coils. Only follow these instructions if you are really desperate. In an 8 wire motor, the coils are split, and to operate it as a unipolar, we have to reconnect the coils to reduce it to a 6 wire unipolar. Assume our eight wire stepper motor wires are colored as follows: Orange, blue, red, green, brown, yellow, white and purple. In an 8-wire stepper motor, these wires would be part of 4 coils, 2 wires per coil. We need to determine the cable pairings. We measure the resistance between each wire and are presented with the following values in ohms (these are simply example values):

Wire Color	Orange	Red	Yellow	Purple	Blue	Green	Brown	White
Orange		∞	∞	∞	1	∞	∞	∞
Red			∞	∞	∞	1	∞	∞
Yellow				∞	∞	∞	1	∞
Purple					∞	∞	∞	1
Blue						∞	∞	∞
Green							∞	∞
Brown								∞
White

This table tells us which wires are parts of a coil. From the table we can tell that orange/blue, green/red, brown/yellow, and white/purple are the coils.

Of each pair, one of the wires will be assigned to A, B, C, or D, and the other wire will be connected to another pair. The number of combinations to be tried to see if they produce rotation is large, but can be reduced to a maximum of 96 possibilities by following these steps:

1. Choose Red/Blue to connect to A. (2 possibilities)
2. Choose one wire of the other pairs (6 possibilities) and connect to B. The other wire from this pair is connected to the wire from Step 1 not connected to A.
3. Choose one wire from the two remaining pairs (4 possibilities) and connect to C.
4. Choose one wire from the remaining pair (2 possibilities) and connect to the wire from Step 3 not connected to C. The remaining wire from this pair is connected to D.
5. After trying each permutation, engage the motor from software and try to rotate it. Since you are driving the motor as Unipolar, the connected pairs should be connected to the (+) on the PhidgetStepper Controller.
6. If you attempt to use this algorithm, build a table of permutations beforehand and proceed in a systematic way.

There are a total of 96 wiring combinations, of which there are 2 valid combinations where one will cause a clockwise motor rotation and the other will cause a counter-clockwise rotation.

In order to properly determine the proper wiring for your motor we suggest consulting any manuals or data sheets that are associated with your particular motor.

Controlling Steppers

Stepper motors precision are limited by the manufacturing process used to build them. Errors in the rotor and coils will cause some degree of inaccuracy. In our experience, inexpensive stepper motors will often have positioning errors approaching a half-step.

Since stepper motors do not have the inherent ability to sense their actual shaft position, they are considered open loop systems. This means that the value contained in the current position property is merely a count of the number of steps that have occurred towards the target value; it can not be relied upon as a measure of the actual shaft angle, as the motor can occasionally understep or overstep due to forces such as inertia.

For many applications, it is acceptable for the motor to miss a few steps. In applications where positional accuracy is vital, there are several ways of overcoming this drawback. The simplest is to allow the motor load to depress a limit switch located at a known position. This can be used to fire an event in software to recalibrate the shaft position values. A more elegant solution might involve the mounting of an optical encoder on the shaft and the development of a control system.

Stepping Mechanism

The 1062 PhidgetStepper Unipolar controls stepper motors in half-step increments. A Position increment of one corresponds to one half-step. A stepper motor with 15 degree step increments will rotate in 7.5 degree steps. The 1062 accomplishes this by alternating the number of powered coils between one and two, always at least one coil powered. In this way, the rotor is positioned at both full steps and half steps. The table below describes the order in which coils are powered to achieve this.

Step Number	Coil A	Coil B	Coil C	Coil D	Shaft Angle
1	ON	OFF	ON	OFF	0º
2	ON	OFF	OFF	OFF	7.5º
3	ON	OFF	OFF	ON	15º
4	OFF	OFF	OFF	ON	22.5º
5	OFF	ON	OFF	ON	30º
6	OFF	ON	OFF	OFF	37.5º
7	OFF	ON	ON	OFF	45º
8	OFF	OFF	ON	OFF	52.5º

After step number 8 in the table, the order the coils are powered in simply repeats from the beginning. As the motor approaches the requested position, it is decelerated according to the value of the acceleration property. When the desired position has been reached, the 1062 stops the motor and holds it at that position.

Synchronization of Multiple Motors

Many applications call for several steppers motors operating in unison - for example, operating a CNC table, or a robot arm. Highly precise synchronization of steppers using the PhidgetStepper is not possible, as the sequencing will be affected by the real-time performance of your operating system. Each stepper is controlled as a independent unit, so there is no way of arranging for a particular action to happen to all motors at the same time. Typical jitter can be 10-30ms.

Compatibility Guidelines

When looking for a motor that will be compatible with the 1062, check the motor's data sheet and make sure it meets the following specifications.

• Unipolar motor - The 1062 can only be used with resistive-limited unipolar stepper motors.
• 5, 6, or 8-wire motor - A 4-wire motor cannot be used with the 1062, because the centre taps of the coils are not exposed.
• Rated/Recommended Voltage - If the motor comes with a rated or recommended voltage, it should be no more than 12 volts, and you should use a power supply that can output that voltage.
• Rated Current - The motor should be rated for a maximum of 1A per coil.

Further Reading

For more information about stepper motors and how they work, check the Stepper Motor and Controller Primer.