Application Notes. -DM01 Linear Shape Memory Alloy Actuator with Basic Stamp Microcontroller Kit

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Application Notes -DM01 Linear Shape Memory Alloy Actuator with Basic Stamp Microcontroller Kit MIGA Motor Company Strawberry Creek Design Center 1250 Addison St.

1 Application Notes -DM01 Linear Shape Memory Alloy Actuator with Basic Stamp Microcontroller Kit MIGA Motor Company Strawberry Creek Design Center 1250 Addison St., Studio 208 Ph: (510) Fax: (510) This is a preliminary engineering release. The information contained herein is believed to be accurate at the time of printing, but the company reserves the right to change specifications without prior notice. The intellectual property described in this document is covered by U.S. and international patents, issued and pending, trademarks, and copyright laws as appropriate.

Rev. A DM01 Operating Guide Page 2 of 7 3/1/07 DM01-Series Actuator with Parallax Board of Education µcontroller Application Notes Section 1 Introduction The DM01 actuator has a very simple two-wire

2 Rev. A DM01 Operating Guide Page 2 of 7 3/1/07 DM01-Series Actuator with Parallax Board of Education µcontroller Application Notes Section 1 Introduction The DM01 actuator has a very simple two-wire interface, which simply allows the input of power to the Shape Memory Alloy (SMA) wires. When power flows through the SMA wires, the electrical resistance causes them to heat up and contract. If the actuator is unconstrained, it will return to the starting point as the wires cool and relax. The SMA wires are capable of exerting more force than the rest of the actuator can withstand, breaking welds or other elements of the actuator. As general practice, NOT BUILD MECHANICAL STOPS into the system or damage may occur. Implement actuation stops electronically with sensors and power control instead. The following sections will outline some ways to do this using the Parallax BASIC Stamp HomeWork Board. It is also possible to precisely control the contraction speed of the actuator, outlined in Section 4. Drivers and BASIC Stamp manuals are available online at specifically: and Section 2 Basic Setup This example runs the actuator on a timed contract/release cycle while outputting the measured actuator position to the debugging terminal. Assemble the circuit as shown in Figure 1 on the breadboard of your BASIC Stamp HomeWork Board. Make sure to bolt the heat sink onto the TIP120 transistor with the Figure 1: Position sensing and actuation control included #2-56 nut and bolt. The circuit. position sensor is the 10k ohm linear pot included in your kit. Mount the potentiometer

3 Rev. A DM01 Operating Guide Page 3 of 7 3/1/07 such that the body is fixed to mechanical ground, and the moving wiper moves along with the DM01 output shaft, or with some other component of your device depending how you want the control loop to operate. Once the circuit is assembled, software needs to read P7 and set P14 in order to measure the Position Sensor and actuate the DM01. Enter and run DM01A_TimedCycle.bs2 on the Stamp (refer to your stamp manual, available at Parallax.com, for instructions on programming your BASIC Stamp). ' DM01 Adapter Board - DM01A_TimedCycle.bs2 ' Cycle the DM01 and measure the position. cnt VAR Word actuate VAR Word HIGH 7 ' Linear pot position measurement ' Cycle counter ' Indicate whether DM01 on or off ' charge RCTime capacitor ' Begin main loop. PAUSE 20 ' Pause for charge ' Measure discharge HIGH 7 ' Reset pin 7 DEBUG CLS, "Position = ",DEC pos ' Display position IF actuate = 1 AND cnt > 20 THEN ' Actuation finished LOW 14 ' Turn off DM01 cnt = 0 ' Reset the count actuate = 0 ' Indicate off ELSEIF actuate = 0 AND cnt > 200 THEN ' Finished relaxing HIGH 14 ' Turn on DM01 cnt = 0 ' Reset the count actuate = 1 ' Indicate the actuation is on cnt = cnt + 1 ' Increment the count Section 3 Intermediate Setup This example actuates the DM01 between end-limits as quickly as it naturally can. This setup uses the same hardware configuration as in Section 2, but is more advanced and requires careful observation (in order to prevent damaging your actuator). While running the basic setup, observe the position value and record the minimum and maximum values displayed these are your end-limits, and should be about 510 and 115 units, respectively (depending on the capacitor used in the RC section of the linear pot). Adjust them each by 5 units towards the center (i.e. 505 and 120) as a safety buffer and use these values for limhigh and limlow. Enter and run DM01A_LimitCycle.bs2 with your own values for limhigh and limlow.

4 Rev. A DM01 Operating Guide Page 4 of 7 3/1/07 ' DM01 Adapter Board - DM01A_LimitCycle.bs2 ' Cycle the DM01 between high and low limits. limhigh CON 505 limlow CON 120 ' Linear pot position measurement ' Contraction limit ' Relaxation limit HIGH 7 ' Initialize pin 7 ' Begin main loop. PAUSE 20 ' Pause for capacitors to charge ' Measure position HIGH 7 ' Reset pin 7 DEBUG CLS, "Position = ", DEC pos ' Display the measured position IF pos > limhigh THEN LOW 14 ELSEIF pos < limlow THEN HIGH 14 ' DM01 has finished actuation ' Turn off DM01 ' DM01 has finished relaxing ' Turn on DM01 The higher the power of your voltage source, the faster the actuator will operate try playing with different input voltages (always starting at low, slow values) and observe the behavior of the actuator. Section 4 Advanced Hardware Setup This example sends a full powered pulse to the actuator whenever the electrode is touched and measures the maximum displacement. Adjusting the power supply voltage will demonstrate the effect varying current levels have on contraction speed. This setup requires more complicated circuit construction, but is very simple to program. Assembly the circuit shown in Figure 2 on the breadboard of your BASIC Figure 2: Touch sensor and control loop circuit schematic. Stamp HomeWork Board, and confirm the linear potentiometer is mounted as described in section 2. The electrode can be almost any piece of conductive material try experimenting with different items lying around. Note that you do not need to make physical contact with the electrode to activate it: the conductor may even be covered with a thin insulator. Once the hardware is in place, enter and run DM01A_Pulse.bs2 on the Stamp.

5 Rev. A DM01 Operating Guide Page 5 of 7 3/1/07 ' DM01A_Pulse.bs2 ' Full power on for a specified time whenever a button is depressed ' Measured position variable IF IN2=0 THEN ' Electrode activated HIGH 7 ' Charge position capacitors PULSOUT 14,50000 ' 100ms pulse (maximum is ms) PULSOUT 14,50000 ' 100ms pulse makes 200ms PULSOUT 14,50000 ' 100ms pulse makes 300ms total ' Discharge time yields position DEBUG CLS,"Maximum = ",DEC pos ' Display the maximum position PAUSE 2000 ' Prevent rapid successions of pulses ' Continue forever Try changing the voltage of your power source and watch how the maximum displacement displayed on the debug terminal and the rate of contraction change. This is because more thermal energy is deposited into the wire, increasing its temperature more. Note that this relationship is not linear; when energy is added faster, the temperature goes up exponentially because there is less time for the wire to dissipate heat, and more of the input energy goes into changing the phase of the wire. Section 5 Advanced Software and Hardware Setup This example uses a touch sensor (electrode) to cause the DM01 to actuate at a constant speed while the electrode is touched, and hold position when the electrode is bare. Pressing the reset button on the HomeWork Board will reset the actuator and allow it to relax. The software limits will prevent damage to the DM01. Warning: do not leave the circuit powered in the intermediate state for too long: you can build in a software timeout of seconds to prevent this condition. Assemble the circuit as shown in the schematic in Figure 2 as described in Section 4. Enter and run DM01A_SpeedAndHold.bs2 with your own values for limhigh and limlow (from Section 3). ' DM01 Adapter Board - DM01A_SpeedAndHold.bs2 ' Move at controlled speed when button active. ' Hold position when button released. ' Reset to beginning when reset pressed. setinc VAR Word set VAR Word err VAR Word PWMDuty VAR Word timeout VAR Word ' Position measurement ' Setpoint used for incrementing ' Setpoint used for position ' set/setfactor - pos ' Duty cycle for the PWM signal ' keeps track of running time

6 Rev. A DM01 Operating Guide Page 6 of 7 3/1/07 speed CON 25 setfactor CON 10 Kp CON 1 limhigh CON 505 limlow CON 120 ' Speed to move at ' Real setpoint = set/setfactor ' Proportional gain ' Contraction limit ' Relaxation limit HIGH 7 ' Initialize pin 7 setinc = limlow*setfactor ' Initialize to lower limit set = limlow ' Initialize to lower limit timeout = 0 ' Initialize ' Begin main loop. IF set > limlow THEN ' Actuator is powered timeout = timeout + 1 ' Increment timeout counter ELSE timeout = 0 ' Reset count because unpowered IF timeout > 1100 THEN ' After 30 second of activation... set = limlow ' Reset the set points setinc = limlow*setfactor ' Reset the set points timeout = 0 ' Restart timeout count ' Measure discharge HIGH 7 ' Reset pin 7 'DEBUG CLS, "Position = ",DEC pos ' Display the measured position 'DEBUG CR,"Setpoint = ", SDEC set ' Display setpoint IF IN2 = 0 AND set<limhigh THEN setinc = setinc + speed ' Advance at desired speed set = setinc/setfactor err = set - pos IF err >= THEN PWMDuty = 0 ELSE PWMDuty = err*kp ' Negative rollover IF PWMDuty > 255 THEN ' PWM only accepts up to 255 PWMDuty = 255 IF pos > limhigh THEN LOW 14 ELSE PWM 14, PWMDuty, 20 ' DM01 has finished actuation ' Turn off DM01 ' Actuate with a PWM Try adjusting the speed and Kp variables to see how the DM01 reacts. You can also try adding more advanced logic, such as having the set-point reset automatically once the limit is reached, or allowing the touch sensor input to increase the speed, such that the actuator will continue moving at constant speed when the electrode is bare.

Rev. A DM01 Operating Guide Page 7 of 7 3/1/07 Parallax Board of Education Micro-Controller Kit (MIGA components not shown) DM01 linear actuators are a well-proven and reliable technology, but we can

7 Rev. A DM01 Operating Guide Page 7 of 7 3/1/07 Parallax Board of Education Micro-Controller Kit (MIGA components not shown) DM01 linear actuators are a well-proven and reliable technology, but we can t predict the numerous applications in which they will be used. Please contact us for assistance in safely using the DM01 in your application. When used properly, the DM01 actuators will provide many cycles of trouble-free operation. We hope you find that MIGA Motor Company devices are the solution to your motion problems. The recommendations, data, and specifications in this publication are believed to be accurate and reliable. However, it is the responsibility of the product user to determine the suitability of MIGA Motor Company products for a specific application. While defective products will be promptly replaced without charge if promptly returned, no liability is assumed beyond such replacement. These products are protected by one or more of the following patents: 6,326,707; 6,574,958; 6,762,515; 6,832,477; 6,928,812; 7,021,055; 2,391,746 (Canada); 772,107 (Australia); (China); EP 1,203,156 (EU); / (Taiwan) and others pending. Contents and trademarks copyright 2007 MIGA Motor Company. All rights reserved.

Flexiforce Demo Kit (#28017) Single Element Pressure Sensor

Flexiforce Demo Kit (#28017) Single Element Pressure Sensor 599 Menlo Drive, Suite 100 Rocklin, California 95765, USA Office: (916) 624-8333 Fax: (916) 624-8003 General: info@parallaxinc.com Technical: support@parallaxinc.com Web Site: www.parallaxinc.com Educational: