with SensorDAQ - Vernier Software & Technology
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1. so positive current would flow from D2 to D1 This idea allows you to have motors run in either of two directions Two Digital Output Lines Used to Run a Motor in Two Directions Connecting Devices to the DCU For connecting electrical devices use the 9 pin sub D socket on the side of the DCU There are connections for all six digital lines plus power and ground The diagram below shows the connections to the holes on the socket on the cable not the pins on the DCU box G G The End of the Cable that Plugs into the DCU Looking into the Holes The holes labeled 1 2 3 4 5 and 6 are the digital output lines G is for ground and is for the power from the power supply of the DCU We provide one cable to plug into this socket with the color code of the wires identified on a label attached to the cable For testing twisting the wires together is probably ok but eventually you will want to solder the leads or make some other connection Whatever you do make sure you insulate the leads so that they cannot accidentally touch each other We recommend using a terminal strip like the one shown below As you build devices to connect to the DCU always keep the power limitations of the DCU in mind For the entire DCU it should not exceed the current limit of your power supply This limit is 300 mA when using the CBL 2 power supply 600 mA when using the LabPro power supply and 1000 mA when using the ULI power supply If you are us2. On the second iteration the value is 1 which turns on line 1 This is followed by a 2 which turns on line 2 a 3 which turns on lines and 2 and so on and so on until it reaches 15 At that point all 16 DCU line combinations have been turned on and the For Loop is terminated Once the For Loop has completed the last piece of code becomes active STOP is a driver subVI whose function is to properly end the program turn off any DCU lines left on and shut down the SensorDAQ Using the DCU Driver SubVIs When building or modifying a program in LabVIEW it is easy to locate all of the DCU driver subVIs in the User Libraries function palette To find this palette simply right click in the Block Diagram If you do not know where to find the User Libraries function palette click on the LabVIEW function palette s Search button and do a search for DCU xj DCU palette Note that in the DCU palette there are sub palettes containing DCU driver subVIs to control a single line take a sensor reading and to control a motor Here are a few examples of using the various DCU driver subVIs ine 1 TruelFalse Example 1 User turns line 1 on and off with a Front Panel Boolean control The program continues until the Front Panel stop button is pressed Select Channel above Threshold Example 2 Line I will turn on if a sensor reading from Ch I is above a user defined threshold Line I is off if the sensor value is below the t
3. demonstrate how to collect data from a sensor and then perform a specific digital output based on the sensor reading include DCUSUN DCUTEMPC and DCUWARNV Additional SensorDAQ Sample VIs The SensorDAQ CD contains LabVIEW VIs that show how to program most of the major features of the SensorDAQ including data collection analog output digital input and output using the counter and using other hardware on the DIG Channel Refer to the SensorDAQ User Manual to learn about these examples Using DAQmx The DAQm x driver is at the heart of SensorDAQ control If you are more comfortable with programming with the DAQmx drivers you can find DAQmx examples in the SensorDAQ folder in the LabVIEW user lib directory LabVIEW Troubleshooting Help e Make sure the DCU power supply cable is attached 10 e Ifthe SensorDAQ LED does not blink the DAQmx driver may not be properly installed Try re installing the driver Reboot the computer after installing the driver Review the SensorDAQ manual for specific installation instructions e Ifthe SensorDAQ LED is blinking but the LabVIEW examples do not detect SensorDAQ unplug SensorDAQ s USB cable reboot the computer then reinsert the USB cable to SensorDAQ e A bug in DAQmx versions between 8 6 and 8 7 turns on line 3 when the INIT driver subVI is called To negate this the device is reset in the STOP subVI However this appears to turn on line 5 when the program ends Additional Notes on C
4. line is disconnected The outputs 0 through 11 can be considered as the binary equivalent of the number with D1 used for the least significant bit D2 used for the second digit D3 for the third and D4 as the most significant bit Outputs 0 through 7 give totally independent control of the first three digital lines Outputs 12 through 15 are designed for controlling just D5 and D6 but do not allow any use of the first four lines One reason for this choice is to allow for building robot cars With such a car you might want one wheel to be controlled by D1 and D2 and another to be controlled by D3 and D4 It would still be useful to have some other lines that could be used for other operations Lines D5 and D6 do this but these lines can only be used when lines D1 through D4 are off With this setup you could build a robot that can move around using lines D1 thru D4 and then when it reaches a destination it can do a separate action For example you could turn on a buzzer turn on a light or run a third motor Pairs of DCU lines can be used together to allow you to switch the polarity or direction of current flow in an electrical device Consider the circuits below Both circuits show an electrical device wired between the D1 and D2 lines of the DCU The circuit at the 4 left has the D1 set for and D2 set for so positive current would flow from D1 through the device and to D2 The circuit on the right has D1 set for and D2 set for
5. Using the Digital Control Unit DCU with SensorDAQ Measure Analyze Learn Vernier Software amp Technology 13979 S W Millikan Way Beaverton OR 97005 2886 Toll Free 888 837 6437 e 503 277 2299 e FAX 503 277 2440 info vernier com www vernier com The Digital Control Unit Manual is copyrighted 2001 2008 by Vernier Software amp Technology All rights reserved Purchase of the Digital Control Unit and accompanying manual and CD includes a site license entitling the teachers at one school to reproduce the programs source code and manual for use at that one school only No part of this manual or its accompanying CD may be used or reproduced in any other manner without written permission of Vernier Software amp Technology except in the case of brief quotations embodied in critical articles or reviews Vernier SensorDAQ and SensorDAQ are a trademark of Vernier Windows is a trademark of Microsoft Corporation in the United States and or other countries LabVIEW is a trademark of National Instruments Inc All other names mentioned are trademarks or registered trademarks of their respective holders in the United States and other countries Published by Vernier Software amp Technology 13979 SW Millikan Way Beaverton Oregon 97005 2886 503 277 2299 888 837 6437 www vernier com info vernier com Second Edition 2008 First Printing Printed in the United States of America Acknowledgements The Digital Control Uni
6. bVI A popup dialog box will appear The Context Help for the INIT driver subVI will look like this Parameters error que aa en SensorDAQ Connected error in DCU Init vi Start your OCU programs with this subyI Information is stored in the Error and Parameters output wires You must wire these in and out of the next OCU subyT in your program Continue to wire these two lines in and out of all of the DEU subis Wa It is a good idea to use the Context Help to help you understand the various inputs and outputs of all of the driver subVIs and also the LabVIEW functions The LINES 1 6 driver subVI is called next It is used to turn on and off the DCU output lines It is encased within a For Loop that will execute 16 times On each execution of the For Loop the LINES 1 6 driver subVI is called and is configured to turn on a line s for a set amount of time The amount of time that the lines are turned on is determined by the value input into the Duration input The user Sets this value from a control located on the Front Panel What line s is turned on is determined by the output value of the For Loop s iteration terminal this is the 1 in a small blue box icon This terminal keeps track of how many times the For Loop has iterated and it ranges from 0 to N 1 Therefore on the first iteration of the For Loop the value sent from the iteration terminal to the LINES 1 6 driver subVI is 0 This turns all lines off
7. e side of the DCU power supply to the negative side of the power supply or left unconnected There are six switches of this type inside the DCU These are not mechanical switches but rather electronic switches using transistors that function like the mechanical switch illustrated above If you connect an electrical device between the DCU line and a ground connection you can control whether it is on or off If the switch is in the position current will flow and the device will be on Either of the other two positions will turn it off If you have read the specifications in the documentation that came with the SensorDAQ you may be surprised to see that there are six digital output lines on the DCU This may be surprising because the DIG port of SensorDAQ has only four digital output lines However we do some digital logic tricks that allow us to control six instead of four lines Of course we had to pay a price for this trickery We do not have totally independent control of all six lines This compromise allows us independent control of the first three lines any combination of the three can be turned on and then allows us to use the other three with restrictions The easiest way to see the restrictions is to examine the 16 possible output patterns from the DCU eF indicates the line is connected to the positive voltage of the DCU power supply indicates the line is connected to ground negative lead of the DCU power supply and X means the
8. error method to figure out the wiring pattern Wire them as shown below There are three different methods of driving a stepper motor Normal Half Step and Wave Drive The DCUSTEP and DCUSTEP3 programs use the Normal method In this case electromagnets inside the stepper motor are always turned on two at a time as the motor steps In the Half Step Method intermediate steps with only one electromagnet on at a time are included This gives you more precision in the positioning of the stepper motor The Wave method of driving a stepper motor has only one electromagnet on at a time For this reason the Wave Drive method uses less electricity but the motor will have less torque Below are the DCU output patterns to use for rotating a stepper motor clockwise and counterclockwise in each of the three drive modes We use the Normal drive method in all our programs but you may want to try the others For Normal Stepper Motor Rotation e 5 9 10 6 for clockwise e 6 10 9 5 for counterclockwise For Half Step Stepper Motor Rotation e 5 1 9 8 10 2 6 4 for clockwise e 4 6 2 10 8 9 1 5 for counterclockwise For Wave Drive Stepper Motor Rotation e 1 8 2 4 for clockwise e 4 2 8 1 for counterclockwise There are other ways to connect stepper motors If you use a stepper motor control integrated circuit IC you will need fewer wires to control the stepper motors This will allow you to control two stepper motors with the DCU One t
9. h America different versions available for other parts of the world e CBL 2 power supply 6V regulated 300 mA TI Model AC 9201 e ULI power supply 9V unregulated 1000mA Vernier order code ULI PS e Battery power supply one lantern battery or a collection of four to eight 1 5 volt cells in series To make the cable from the batteries to the DCU you need to use a 5 5 mm x 2 1 mm power connector Radio Shack part number 274 1569 Connect the leads so that the center of the connector is negative The voltage supplied can be between 5 volts and 12 volts Never apply more than 12 volts DC to the DCU Never use AC power supplies with the DCU Note that the center connector on the DCU socket for connecting to a DC power source is negative The total current drawn by everything plugged into DCU should not exceed 600 mA Digital Output Lines The transparent top of the DCU reveals six red LEDs and a green LED The green LED comes on when the DCU is properly connected to the SensorDAQ and to a power source Learn to check the green LED to insure proper set up l No Di DCU Connections ae ale The red LEDs indicate the status of the six digital output lines We refer to the six digital output lines as D1 D2 D3 D4 D5 and D6 You can think of the DCU as a set of six remote controlled switches Each of the six lines from the DCU is connected to a switch that can have any one of three positions The line can be connected to the positiv
10. he projects we have built at version 1s best to use if you plan to use the stepper motor for several different Vernier You probably have some better motions one after the other id f DCUSUN Centers a light source between two light sensors using two auto ID Vernier A a aa light sensors connected to Ch 1 and Ch 2 and a DC motor connected to the D1 e Mass driver to accelerate a and D2 output lines of the DCU magnet DCUTEMPC Creates a temperature controlled environment It turns on a heater D1 if temperature is below minimum temperature and turns on a fan D2 if e Stepper motor DC motor or servo temperature is above maximum value motor control system you wire up to the DCU EA Onac DCUWARNV Monitors an analog signal and turns on the D1 output of the DCU if the level nied exceeds a limit This is a good sample program to start with for any project e Alarm system using a buzzer or involving monitoring an analog signal and taking action based on the reading LED to warn when an event occurs e Live traps for small animals or bugs activated by a sensor e Automatic tea brewer e Automated scientific instruments and demonstration equipment e Light seeking to follow the sun e Moving display and kinetic sculptures e Automated battery tester e Roving robot with sensors Collecting Data to Control Outputs Some of the most interesting programs include the use of sensor data for feedback and control Example programs that
11. hreshold value The program continues until the Front Panel stop button is pressed Example 3 The user controls a servo motor with a Front Panel control In addition sensor readings from Ch I and Ch 2 are continually collected The program continues until the Front Panel stop button is pressed Additional Notes on LabVIEW Programming Sample Program Descriptions The names of all the DCU manual examples we have provided start with the letters DCU and have eight or fewer characters Below is a list of all sample programs Digital Control Unit Programs In addition to these examples you will find Allows control of a car driven by two DC motors using the four arrow keys further examples in the subfolder named The program assumes your car has a DC motor powering each drive wheel Examples Open and study these simple DCUCOUNT Sends each of the 16 possible digital outputs to the DCU lines Counts 0 15 to programs show the resulting LED displays DCUMASS Turns on D1 D2 D3 and D4 in order to accelerate a magnet through a tube DCU Project Ideas mass driver DCUSERVO Controls a servo motor connected to D1 Over the years we have used the Digital DCUSTEP Allows you to specify direction and number of steps for a directly connected Control Unit for dozens of projects some stepper motor unipolar or bipolar whimsical and some practical Here are DCUSTEP3 Controls a stepper motor and keeps track of stepper motor positions This some of t
12. ing a different power supply check the current rating In general you will not damage the DCU by trying to draw too much current but the circuit will not work properly It may also be possible that you could damage the power supply The current draw for any one line should not exceed 600mA no matter what Remember that Ohm s law controls the current that flows through the device Current amperes Voltage volts Resistance ohms 5 In some cases you can check the resistance of the device with a meter and calculate how much current it will draw using Ohm s law Refer to the Additional Notes on Connecting Devices for specific wiring examples Programming for the DCU LabVIEW is a graphic programming language LabVIEW programs are known as Virtual Instruments or VIs A LabVIEW VI has two main parts the Front Panel and the Block Diagram The Front Panel is the user interface with buttons and controls and also displays The Block Diagram is the code controlling how the VI functions We have provided a collection of example VIs that control the DCU If you study the Block Diagram of the DCU Example VIs you will see that they are made up of our DCU driver subVIs that perform the low level commands to the SensorDAQ The three driver subVIs that are the building blocks of many of our DCU programs are shown below Wiring these driver subVIs together and providing a few inputs can easily build a simple DCU program The inputs int
13. lude the positioning of the head on a disk drive or the laser in a CD ROM player There are basically two types of stepper motors that you may want to use unipolar and bipolar You can identify which type you have with this rule e Bipolar stepper motors have 4 lead wires e Unipolar stepper motors have more than 4 wires usually 5 6 or 8 No matter what type of stepper motor you have remember that it needs to match the voltage you are using on your DCU power supply If you are using the LabPro CBL 2 power supply you should use 6 volt stepper motors Identifying the leads on a stepper motor can be tricky It helps if you have a diagram provided by the manufacturer Unfortunately 11 you are often using a surplus stepper motor and need to figure it out yourself First determine which type of stepper motor it is Next look for patterns Examine the wires carefully Refer to the diagrams below which symbolically show how the two types of stepper motors are wired inside Use a meter to measure resistance Remember that a coil will have a few ohms of resistance Use a little trial and error and you will be able to get it going Bipolar Stepper Motors To connect a bipolar stepper motor directly to the DCU wire it as shown here Unipolar Stepper Motors Unipolar stepper motors are more difficult to figure out for wiring than bipolar ones Often all the ground wires are the same color or similar colors Use a meter and the trial and
14. o the LINES 1 6 driver subVI determines what lines are turned on and whether these lines are on for a set amount of time or on indefinitely Here is an example of inputs into the LINES 1 6 driver subVI that would turn on line 6 for 2 seconds Select Timing Option 4 Lines On For Set Amount of Time OU Oukput Pattern 0 15 Set Time On Crnilliseconds Notice the number input as the DCU Output Pattern This number comes from the Output column of the table that was introduced in the DCU Overview section The value of this number determines what line s is turned on and off A value of 14 turns on line 6 Trying out a LabVIEW Program DCUCOUNT To see a LabVIEW program in action controlling the DCU try the DCUCOUNT VI This VI runs through all of the possible patterns of the DCU First prepare your hardware 1 Connect the DCU with power supply to the connector on the side of the SensorDAQ labeled DIG Make sure this connector locks in place 2 Connect a SensorDAQ to the computer using the USB cable Now navigate to the location of the DCU examples C Program Files National Instruments Lab VIEW x x user lib DCU Examples_DCU Manual Inside you will see a number of files Double click on the file named DCUCOUNT v1 This will start LabVIEW with the DCU program open You will see the front panel of the LabVIEW program he HOE OS oe h Pd Thee Deru k Control Lind prerai current Gap te G00 ond bon i
15. onnecting Devices Connecting One Simple Non Polarized Device To connect a simple non polarized electrical device such as a lamp DC motor not a stepper or servo motor resistor or electromagnet that you just want to turn on or off use this wiring pattern Connecting a Polarized Electrical Device Some electrical devices are polarized that is they have a positive and a negative side They therefore must be wired in one particular way for use with the DCU Examples include some buzzers a few lamps LEDs and complex electronic devices For devices that have positive and negative sides make sure you connect the negative side to ground Connecting a Motor for Running in Either Direction Simple DC motors can be wired as shown above and they will either be off or on rotating in one particular direction If you want to have the ability to run the motor in either direction you have to wire it as shown below For a motor wired this way you will get one direction of rotation if D1 is high and D2 is low You will get the opposite rotation if D2 is high and D1 is low It will be off for all other patterns You can connect a second motor wired this way to D3 and D4 and even a third motor connected to D5 and D6 Connecting Stepper Motors Stepper motors are very different from simple DC or commutator motors that have two lead wires Stepper motors are used in cases where you want to have exact control of a motion Examples inc
16. pnthilieg a dete Lh cerns bo the GA dare ol Termania raie Hee Cec ere Ls Het iid Hee chats of ee a Cnr ines hi the eee you cen a the dunabon of current pent te the aetna Em m Eh DS ee ae cg el ples cpa ete Piire i Tonna Hee Ga een re a che h err ae Da 3 Foun fhe V0 ep icon He setae ars boi ii The bleen ERS r iiia ia Pht ir et Front Panel of DCUCOUNT vi Let s try running this VI Click on the Run button white arrow at the left side of the toolbar This will start the VI running and you should see the green LED on the Front Panel labeled SensorDAQ Connected turn on Refer to the LabVIEW Troubleshooting Help section of this manual if your program does not make a connection with SensorDAQ This program will cycle through all of the patterns of lines that are available with the DCU Note that there are some combinations that are not allowed see the table of digital outputs in the DCU Overview section Examining the DCUCOUNT LabVIEW Code Clicking on the Run button began the code that flashed all available DCU output patterns So now let s take a look at this code found in the Block Diagram an easy way to toggle between the Front Panel and Block Diagram is to press the Control E keys a 2 GensorDAQ Connected SensorDAQ Connected ELE Block Diagram of DCUCOUNT vi The execution order of this program is left to right but this is not controlled by the position of the subVIs or f
17. sorDAQ placed in the LabVIEW user lib directory These steps are outlined in the SensorDAQ User Manual Setting Up the Files The folder called DCU contains the simple drivers for controlling the DCU and sample LabVIEW programs demonstrating these drivers The DCU folder can be found on the CD that came with the DCU open the SensorDAQ DCU folder or on the Vernier engineering web site at engineering vernier com general software labview 1 Locate or download the folder named DCU 2 Copy the DCU folder to your LabVIEW user lib directory C Program Files National Instruments Lab VIEW x x user lib Note If you have Windows 2000 change the property of the folder so that it is not Read Only DCU Overview The Digital Control Unit DCU is a small box with a short cable that plugs into the SensorDAQ DIG channel Next to the cable is a socket for connecting a DC power supply On the side opposite is a 9 pin D sub socket The nine connections of the D sub socket include six digital lines two ground connections and a power connection We supply a cable that connects to the 9 pin D sub socket This cable has bare wires to provide an easy way for you to connect electronic devices The color coding for each wire is shown on a label attached to the cable Power Source The DCU requires an external power source Four different power sources are recommended e LabPro power supply 6V DC regulated 600 mA Vernier order code IPS in Nort
18. t was designed by John Wheeler Dr Fred J Thomas of mathmachines net provided valuable suggestions for the device Thanks to Michele Perin Erik Schmidt and Sam Swartley of Vernier Software amp Technology for their editing and testing Thanks to Adrian Oldknow for encouraging me on this project Thanks also to Scott Webb and Eren Koont of Texas Instruments for their ideas and encouragement on this project David Vernier Vernier Software amp Technology Using the DCU with Vernier SensorDAQ and LabVIEW Introduction This reference guide is to help people who want to use the Vernier SensorDAQ to get their DCU up and running as quickly as possible There is a separate manual for using the DCU with the Vernier LabPro It assumes that the user has minimal familiarity with LabVIEW programming The first section provides an overview of the DCU hardware and connecting devices to the DCU the next section shows how to run examine and modify one of the DCU sample VIs The third section Additional Notes on LabVIEW Programming provides information about the other DCU examples where to look for more SensorDAQ examples and troubleshooting help The final section Additional Notes on Connecting Devices provides a few examples of connecting devices to the DCU Software Requirements There are three steps that must be taken before you can run the DCU examples 1 LabVIEW software installed 2 NI DAQm x software installed 3 The folder called Sen
19. unctions on the block diagram LabVIEW uses data flow programming meaning that a subVI or LabVIEW function will not execute until all of its input data are available This program has one Front Panel control labeled Duration and two Front Panel indicators labeled Output and SensorDAQ Connected The Duration control sets the time that the lines remain on and the Output indicator displays what output value is sent to the DCU The SensorDAQ Connected indicator provides feedback on whether the SensorDAQ was found The program also has two property nodes that reset the values of the two indicators at the end of the program SensorDAG Connected ener The SensorDAQ driver subVI INIT begins the program Driver subVIs contain and hide a lot of low level code This particular driver subVI tests for a SensorDAQ connected to the computer initializes the SensorDAQ and configures the device to control a DCU An important output of the INIT driver subVI is the Parameters cluster The information in this cluster is passed to the other driver subVIs to help them configure and control the SensorDAQ according to the setup parameters To view more information on the driver subVI inputs and outputs and to see more information on the purpose of the driver subVI you can show the Context Help Do this by going to the Block Diagram choosing Help gt Show Context Help from the Menu and placing your cursor over the driver su
20. ype of stepper motor control IC uses 12 just two lines to control the stepper motor One line is held high or low to indicate the direction the motor should rotate The other line is toggled on and off one time for each step the motor is to move Servo Motors Servo motors are very popular in robotics because they have a lot of torque for their size and power used Servo motors are controlled by pulse width modulation that is a square wave on off pattern is sent to their control line The length of time that the square wave is at the high voltage is varied to control the servo motor rotor s position The servo motor will hold its position firmly as long as the square wave continues We can create the necessary square waveform from the DCU The DCUSERVO program is an example It will produce the necessary square wave pattern for most servo motors Connect a servo motor by wiring the motor s power lead to the DCU line the motor s ground lead to the DCU ground line and the signal lead to DCU line D1 This is the connection assumed by the DCUSERVO programs and is shown below 13 NOTES 14
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