TMC428 RS232 MAX232 TMC246 TMC249 TMC-428 MAX-202 EV428 95/98/NT/2000 EVAL428 - Datasheet Archive
Manual Version: 1.13 th April 15 , 2009 Sternstraße 67 D 20357 Hamburg, Germany Phone +49-40-51 48 06 0, FAX:
TMC428 TMC428 Evaluation Kit V3.0 Manual Version: 1.13 th April 15 , 2009 Sternstraße 67 D 20357 Hamburg, Germany Phone +49-40-51 48 06 0, FAX: +49-40-51 48 06 60 http://www.trinamic.com 2 TMC428 TMC428 Evaluation Kit V3.0 Version Version 1.00 1.10 1.12 1.13 Date 2003-12-15 2004-01-16 1-Oct-04 15-April-09 Author OK OK OK LL Remarks Initial version Chapter 4 updated (StallGuard added), Chapter 5 added Minor error corrections PCB outline updated concerning jumper EXTERN / INTERN Table of Contents 1 2 3 Introduction . 3 Quick Start . 4 The Hardware . 5 3.1 Connectors . 5 3.2 Pin assignments of the connectors . 6 3.3 Motor drivers . 6 3.4 Communicating with a PC . 6 4 The PC Software . 7 4.1 The Main Window . 7 4.1.1 An example . 8 4.2 The Graphic Display Window . 9 4.3 The register window . 9 4.3.1 The "Motor 1", "Motor 2" and "Motor 3" pages . 10 4.3.2 The "Global Parameters" page. 10 4.3.3 The "RAM Table" page . 11 4.4 The StallGuard window . 12 4.5 The "Calc428" programme . 13 4.6 The "Eval428EEP" programme . 13 5 The StallGuard Profiler . 14 5.1 Installation . 14 5.2 Usage . 14 5.3 The result . 15 5.4 Interpreting the result. 15 Sternstraße 67 D - 20357 Hamburg, Germany Phone +49-40-51 48 06 - 0, FAX: +49-40-51 48 06 - 60 http://www.trinamic.com TMC428 TMC428 Evaluation Kit V3.0 3 1 Introduction The TMC428 TMC428 Evaluation Kit makes it possible to evaluate and to test all the functions of the TMC428 TMC428. It contains the following components: The evaluation board equipped with the TMC428 TMC428 and three stepper motor drivers A simple two phase stepper motor The Trinamic TechLib CD containing the PC software as well as data sheets and other documents A null modem cable for connecting the evaluation board to the PC On the evaluation board the Atmel ATmega8 microprocessor is used to control the TMC428 TMC428. The microprocessor's FLASH ROM contains a programme which configures the TMC428 TMC428 after a reset and controls the communication with the PC via the RS232 RS232 interface. A PC software running under Windows enables access to all the registers and functions of the TMC428 TMC428 from a PC. Furthermore, some simple functions can be controlled by keys on the evaluation board. Up to two bipolar two-phase stepper motors can be connected. nSCS_C RS232 RS232 (e.g. PC) RS232 RS232 driver (MAX232 MAX232) Microcontroller ATmega8 CLK 8 MHz SCK_C SDI_C TMC428 TMC428 nSCS_S SCK_S SDO_S SDI_S SDO_C Driver Motor 2 TMC246 TMC246 Driver Motor 1 TMC249 TMC249 (with external FETs) Figure 1.1: The structure of the evaluation board M M 4 TMC428 TMC428 Evaluation Kit V3.0 2 Quick Start For a first quick start, connect at least one stepper motor to the connectors MOTOR1 or MOTOR2 (as shown in Figure 3.1). Please note that the stepper motors may only be connected to or disconnected from the evaluation board while the board is disconnected from power, as otherwise the motor drivers could get damaged! Now, connect a power supply of 10.28 VDC and at least 1A to the power connector. The positive pole is marked "+U". When the power supply is working, the "Power" LED will light up. Also the other two LEDs near the buttons will flash once after powering on. Now the following functions can be used: The "MOVE1" key: After pressing the "MOVE1" key, all motors start rotating using different accelerations and velocities and the LED near this button lights up. The "STOP" key: When the "STOP" key is pressed once, all motors will be decelerated using different decelerations. If this key is pressed again while the motors are being decelerated all motors will be stopped immediately. The "MOVE2" key: The functionality of this key is similar to that of the "MOVE1" key, but the motors rotate in the opposite directions and the LED near this button lights up. The functions MOVE1 and MOVE2 are indicated by LEDs. It is also possible to press the other "MOVE" key while the motors are running. The motors will be decelerated and then accelerated in the opposite directions. Stepper Motor Connectors MOTOR2 MOTOR1 Stop Switch Connector 428_SPI_IN TMC246 TMC246 TMC249 TMC249 RB DRIVERS INTERN TMC-428 TMC-428 EXTERN 428_SPI_OUT RA Power Connector RS232 RS232 uC-DIS GND +U ATmega8 µC STOP_L STOP_R MOVE1 MOVE2 STOP MAX-202 MAX-202 Function Keys Figure 2.1: TMC428 TMC428 evaluation board overview Sternstraße 67 D - 20357 Hamburg, Germany Phone +49-40-51 48 06 - 0, FAX: +49-40-51 48 06 - 60 http://www.trinamic.com Power LED TMC428 TMC428 Evaluation Kit V3.0 5 3 The Hardware Please see also the enclosed schematics of the evaluation board (supplied as PDF files on the CD) for a better understanding of this description. 3.1 Connectors The evaluation board is equipped with the following connectors: RS232 RS232 (9-pin Sub-D plug): This is the RS232 RS232 interface for connection to a PC. The interface uses 19200 Baud, 8 data bits, no parity and one stop bit. Only the pins 2, 3 and 5 (RxD, TxD, GND) are connected. +U/GND: socket for power supply. The positive pole is marked "+U". A diode protects the board against wrong polarity. The voltage connected to it must not exceed 28 volts DC. Reference switch connector: Every reference switch pin is pulled to ground by a 1k resistor. The pin assignment of the connector is printed on the board. MOTOR1 and MOTOR2: Stepper motor connectors. Motor #1 is driven by the TMC249 TMC249 driver with external power transistors and the other motor is driven by the TMC246 TMC246 stepper motor driver. ISP-PROG: Atmel ISP connector. This permits changing the microprocessor's firmware using an Atmel ISP. Microcontroller disable jumper (uC-DIS): If this jumper is closed all functions of the microcontroller are disabled and its SPI interface enters a high impedance state. This allows connecting different microcontrollers to be connected to the board so that the TMC428 TMC428 can also be controlled with a different microcontroller. So for normal operation this jumper must be open. "EXTERN/INTERN" jumpers (pls. refer schematic J401, J402): Normally, these jumpers must be in the "INTERN" setting (connecting the middle and the right pin). The other setting is needed to use the "428_SPI_OUT" connector. 428_SPI_IN: Here, an external microcontroller can be connected to the TMC428 TMC428. To use this connector, close the microcontroller disable jumper. The pin assignment of this connector is as follows: Pin Function Pin Function 1 SDO_C (TMC428 TMC428) 2 uC-DISABLE 3 SDI_C (TMC428 TMC428) 4 GND 5 SCS_C (TMC428 TMC428) 6 GND 7 SCK_C (TMC428 TMC428) 8 GND 9 +U (Motor Power) 10 +5V/+3.3V 428_SPI_OUT: The motor driver SPI interface of the TMC428 TMC428 is connected here. So, other drivers can be connected to the TMC428 TMC428 using this connector. To make use of this feature, set the "EXTERN/INTERN" jumpers to the "EXTERN" setting. The pin assignment of the "428_SPI_OUT" connector is as follows: Pin Function Pin Function 1 SDO_S (TMC428 TMC428) 2 uC-DISABLE 3 SDI_S (TMC428 TMC428) 4 GND 5 SCS_S (TMC428 TMC428) 6 GND 7 SCK_S (TMC428 TMC428) 8 GND 9 +U (Motor Power) 10 +5V/+3.3V 3V3: This jumper selects between 5V and 3.3V power for the microcontroller, the TMC428 TMC428, the TMC246 TMC246 and the TMC249 TMC249. If the jumper is open 5V will be used and if the jumper is closed 3.3V will be used. 6 TMC428 TMC428 Evaluation Kit V3.0 3.2 Pin assignments of the connectors The pin assignment of each connector is marked on the board. Please connect the stepper motors to the MOTOR1 and MOTOR2 connectors as shown in the drawing below (Figure 3.1). OB2 OB1 OA2 OA1 M Figure 3.1: How to connect a stepper motor 3.3 Motor drivers The TMC428 TMC428 evaluation board comes with two motor drivers: The Trinamic TMC246 TMC246 and the Trinamic TMC249 TMC249. Both support 4-bit microstepping and stall detection. The difference is that the TMC249 TMC249 uses external power transistors and thus can drive motors with a coil current of more than 1.5A (on this board transistor for max 3A coil current are used). The maximum coil current of the TMC249 TMC249 can be selected using the jumpers RA and RB. It is 1.5A when they are open and 3.0A when they are closed. 3.4 Communicating with a PC The RS232 RS232 interface uses the following communication parameters: 19200 Baud, 8 data bits, no parity bit, one stop bit. The evaluation board expects data telegrams which contain at least one command byte and, depending on the command byte, some data bytes. Depending on the command byte, some data bytes will be sent back as a response. There are the following command bytes (noted in hexadecimal): $23: Send an SPI telegram to the TMC428 TMC428. The evaluation board expects four data bytes which form the SPI telegram that will be sent to the TMC428 TMC428. The response from the evaluation board consists of four bytes which contain the SPI telegram that has been sent back from the TMC428 TMC428. $45(one byte each):Change the contents of the microprocessor's EEPROM. The EEPROM of the microprocessor contains 128 bytes which are copied to the configuration RAM of the TMC428 TMC428 after each reset. may be a value between 0 and 127. The following formula is used to calculate the checksum: =(+) modulo 255 On success ACK ($06) will be sent back, otherwise NAK ($15) will be sent back. $FF: The evaluation board will send a ten byte identification string, containing the firmware version number. Data bytes are not expected by this command. Examples: Reading Motor #0 position register Command from PC: $23 $03 $00 $00 $00 Response from evaluation board: $15 $00 $00 $00 Querying the identification string: Command form PC: $FF Response from evaluation board: EV428 EV428 V2.0 Sternstraße 67 D - 20357 Hamburg, Germany Phone +49-40-51 48 06 - 0, FAX: +49-40-51 48 06 - 60 http://www.trinamic.com TMC428 TMC428 Evaluation Kit V3.0 7 4 The PC Software The PC software supplied with the TMC428 TMC428 evaluation kit is a programme running under Windows 95/98/NT/2000 95/98/NT/2000 and allows access to all the registers of the TMC428 TMC428. You can install the programme simply by copying the file "EVAL428 EVAL428.EXE" from the diskette or CD to your hard disk. After that, the software can be run simply by double clicking the file "EVAL428 EVAL428.EXE". Before starting the software, the evaluation board should be connected to an RS232 RS232 interface of your PC using the null modem cable supplied with the evaluation kit. 4.1 The Main Window After starting the software the main window will be shown (Figure 4.1). First, select the interface to which your evaluation board is connected and click the "Open" button. If the connection to the evaluation board could be established successfully, the message "The board is active" will be displayed. If a message like "The board does not respond" is displayed, please check the power supply and the connection to your PC again (COM1 or COM2?). Now, the TMC428 TMC428 status register is displayed in the "TMC428 TMC428 status bits" section. Using the controls in the "Motor 1", "Motor 2" and "Motor 3" sections, the motors can be run. Just enter all necessary parameters and click the appropriate "Go!" button. You can stop a motor by clicking the appropriate "Stop!" button. Use the buttons "All Go!" and "All Stop" to run or stop all motors simultaneously. Figure 4.1: The main window 8 TMC428 TMC428 Evaluation Kit V3.0 As the evaluation board is equipped with only two motor drivers, the "Motor 3" section will have no effect (but a third motor driver could be added to the board externally). "Motor 1" is driven by the TMC249 TMC249 and "Motor 2" is driven by the TMC246 TMC246. Always select the "Ramp Mode" first, then fill in the other necessary parameters and last start the motor or all motors. You will find an explanation of all the parameters in the TMC428 TMC428 data sheet and also in the example in Chapter 4.1.1. By clicking the "TMC428 TMC428 Registers" button the register window opens and gives you access to every TMC428 TMC428 register (Chapter 4.3). Click on the "Graphics" button to open the graphics window which displays the driving ramps of all motors (Chapter 4.2). 4.1.1 An example In this example it is assumed that a motor is connected to the MOTOR1 connector. First, set the ramp mode of motor #1 to "RAMP". Then enter the following parameters: Target Position: 100000 Vmin: 1 Vmax: 500 Max Accel.: 150 Now click the appropriate "Go!" button. The motor will now be running until position 100000 is reached. After that, enter zero as "Target Position" and click the "Go!" button again. The motor will run back to position zero. You can also try to change the position "on the fly", whilst the motor is running. Just enter a different position, click the "Go!" button and see how the motor reacts. Also open the graphics window (Chapter 4.2) and watch the ramps. Now try also the other modes: The "SOFTMODE" is nearly similar to the "RAMP" mode, except that the motor starts and stops softer. Please note that in the "RAMP" and "SOFTMODE" modes, the "Vmin" parameter must not be zero because otherwise the target position sometimes can not be reached. Hint: Some other parameters which are not displayed in the main window are calculated and set up automatically according to the acceleration parameter. When using the "VELOCITY" mode, you can enter the acceleration and the "Vmax" parameter. The motor is then accelerated to that velocity and keeps running constantly until you change the velocity and click the "Go!" button again. The motor will then be accelerated or decelerated to the new velocity using the acceleration parameter you have entered. If you set the ramp mode to "HOLD", you can only enter the "Actual velocity" parameter, click the "Go!" button and so control the velocity directly. Please see also the files "tmc428_rhz.xls" and "tmc482_rhzva.xls" in the "TMC428 TMC428_Examples" directory of the CD for calculating the TMC428 TMC428 parameters and converting them to or from physical units. Sternstraße 67 D - 20357 Hamburg, Germany Phone +49-40-51 48 06 - 0, FAX: +49-40-51 48 06 - 60 http://www.trinamic.com TMC428 TMC428 Evaluation Kit V3.0 9 4.2 The Graphic Display Window The graphic display window (Figure 4.2) shows the driving ramps of all the stepper motors. The following values are displayed: Green: the actual position of the motor Red: the actual velocity of the motor. The value is shown as an absolute value, so negative velocities will also be shown as positive values Blue: the actual acceleration, also shown as an absolute value Yellow: the actual target velocity of the motor, also displayed as an absolute value Please note that this is only a rough and not an exact diagram. Figure 4.2: The graphic display window The value "Time Interval" shows the time between two pixels on the X axis. This value mainly depends on the performance of the PC and will be slower when the register window is open (the display then gets slower because more values are queried from the evaluation board). The scales of the Y axis are automatically adapted to fit the entire curves. The curves are also displaced one pixel against each other for a better view. If "Stop when velocity = 0" is activated the display will be stopped when the velocities of all motors are zero. All curves are cleared by clicking the "Clear display" button. 4.3 The register window The register window makes the direct access to all TMC428 TMC428 registers possible. It contains five pages on which all registers are displayed sorted by functional blocks. You can read more about the registers in the TMC428 TMC428 data sheet. 10 TMC428 TMC428 Evaluation Kit V3.0 Figure 4.3: The register window showing the "Motor 1" page 4.3.1 The "Motor 1", "Motor 2" and "Motor 3" pages On these pages, all registers belonging to the motors #1, #2 and #3 are displayed (Figure 4.3). In the "Actual Values" and "Read Only Values" sections, the contents of all readable registers are displayed. These values are updated permanently. To change the contents of a register, first click on its name in the "Registers" section. Then change the value in the appropriate edit field in the "New Value" section. You can also copy the actual values into the edit fields by clicking the "Copy" button. In the "SPI Telegram" section, the necessary SPI telegram to set the selected register to the desired value is shown. Click the "Send SPI Telegram" button to send it to the evaluation board, and the value will be set. 4.3.2 The "Global Parameters" page This page (Figure 4.4) contains all the TMC428 TMC428 global parameter registers. It is made up just like the motor register pages. The contents of the read only registers (including the reference switch flags) are shown in the "Read Only" section. In the "Read/Write" section all writable registers are displayed. In the "Actual Values" section the actual contents of the registers are shown and updated permanently. To change a register, just select it in the "Registers" section, then fill in the new value in the "New Value" section. Using the "Copy" button, you can copy the actual contents into the edit fields. In the "SPI Telegram" section, the necessary SPI telegram to set the selected register to the desired value is shown. Click the "Send SPI Telegram" button to send it to the evaluation board, and the value will be set. Sternstraße 67 D - 20357 Hamburg, Germany Phone +49-40-51 48 06 - 0, FAX: +49-40-51 48 06 - 60 http://www.trinamic.com TMC428 TMC428 Evaluation Kit V3.0 11 Figure 4.4: The register window showing the "Global Parameters" page 4.3.3 The "RAM Table" page On this page (Figure 4.5), the internal configuration RAM of the TMC428 TMC428 chip (which contains the driver configuration and the microstepping table) can be viewed and modified. Furthermore, any SPI data telegram can be entered and sent to the evaluation board and the response can be viewed. Figure 4.5: The register window showing the "RAM Table" page Click the "Read from RAM" button to read the contents of the TMC428 TMC428 RAM into the RAM editor. The progress bar below the RAM editor shows the reading progress. After that, the values can be modified. By clicking the "Write to RAM" button, the values will be written back to the TMC428 TMC428 RAM, which is also shown by the progress bar. Use the "Save to file" function to save the contents of the RAM editor to a file and the "Load from file" function to read the file back into the RAM editor. 12 TMC428 TMC428 Evaluation Kit V3.0 The "Microstep Shape" function is used to calculate enhanced microstepping tables. To do this, first set the "Sigma" value to the desired value (any floating point number between 1 and +1). By clicking the "Calculate" button the new microstepping table will be written to the RAM editor only, and by clicking the "Calculate & Write to RAM" button, the values are not only written to the RAM editor, but also to the TMC428 TMC428 microstepping RAM. The driver configuration bytes will not be modified by this process. In the "SPI direct" section, any SPI telegram can be entered and sent to the TMC428 TMC428 by clicking the "Send" button. The response sent from the TMC428 TMC428 is then displayed below the "Send" button. 4.4 The StallGuard window Clicking the "TMC24x StallGuard" button opens the StallGuard window (Figure 4.6). Here the StallGuard features of the TMC246 TMC246 and the TMC249 TMC249 can be explored. Figure 4.6: The StallGuard window For each of the motor driver chips the evaluation board is equipped with the error flags are shown by the blue LEDs and the load value is shown by the red bar in the "Stall Detection". A stall detection threshold can be set with the slider beside the red bar. If the load value shown by the bar reaches the stall detection theshold the motor will be stopped immediately (this is done by the microcontroller firmware of the evaluation board that gets is parameters via the RS232 RS232 interface). The abbreviations at the error flag LEDs have the following meanings: OC-A: Overcurrent on phase A. OC-A: Overcurrent on phase B. OL-A: Open load on phase A. OL-B: Open load on phase B. OC-HS: Overcurrent on high side. UV: Undervoltage. OT-PW: Overtemperature pre-warning. OT: Overtemperature. Sternstraße 67 D - 20357 Hamburg, Germany Phone +49-40-51 48 06 - 0, FAX: +49-40-51 48 06 - 60 http://www.trinamic.com TMC428 TMC428 Evaluation Kit V3.0 13 4.5 The "Calc428" programme The software CD also contains the programme "Calc428". This programme serves as a help to calculate the "PMul" and "PDiv" parameters (see the TMC428 TMC428 datasheet for an exact explanation of these parameters). It can be run simply by double clicking the file "CALC428 CALC428.EXE". Figure 4.7: The "Calc428" programme First, enter the parameters on the left side. After that, click the calculate button and the values will be calculated and displayed on the right side of the window. 4.6 The "Eval428EEP" programme Using the programme "Eval428EEP", you can modify the contents of the EEPROM of the microprocessor on the evaluation board via the RS232 RS232 interface. The contents of the EEPROM are copied to the TMC428 TMC428 RAM after each reset. So, for example, a modified microstepping table could be stored in the EEPROM and will be present immediately after powering on the evaluation board. To do this, you will first have to edit the RAM contents using the RAM editor (see Chapter 4.3.3) and store it in a file. The contents of such a file can then be stored in the EEPROM using the "Eval428EEP" programme. Start the programme simply by double clicking the "EVAL428EEP EVAL428EEP.EXE" file. Figure 4.8: The "Eval428EEP" programme Then select the interface your evaluation board is connected to and make sure that it is connected and powered on. Now select your RAM file either by entering its path directly or by clicking the "Browse" button and selecting a file in the file selection dialogue. Last, click the "Start" button. After a confirmation, the programming process starts. This is also shown by the progress bar. At the end of the programming process, a message dialogue shows if the programming process has been successful. 14 TMC428 TMC428 Evaluation Kit V3.0 5 The StallGuard Profiler The StallGuard profiler is a utility that helps you to find the best parameters for using stall detection. It can be used together with the TMC428 TMC428 evaluation board. 5.1 Installation To install the StallGuard profiler on your PC just copy the file "StallProfiler428.exe" from the TechLib CD to your hard disk. To start it, just double click the file "StallProfiler428.exe". There is no special installation procedure needed. The programme can only be used together with the TMC428 TMC428 evaluation board V3.0 or higher. 5.2 Usage After starting the programme its window appears. First make sure that your evaluation board is connected to the PC and supplied with power. If you would like to change some parameters of the TMC428 TMC428 that can not be changed using this programme, do this by using the Eval428 programme before using this programme (do not power off the evaluation board after that). Then select the COM port to which the evaluation is connected and click the "Open" button. Now the connection to the evaluation board will be established. Figure 5.1: The StallGuard profiler window To record a StallGuard profile, first fill in the necessary parameters: Motor driver: Select the motor driver on the evaluation board which you would like to use. As the evaluation board is equipped with a TMC246 TMC246 and a TMC249 TMC249, it can either be TMC246 TMC246 or TMC249 TMC249. Make sure that your motor is connected to the driver you would like to use. Start velocity: This is the velocity value that is used at the beginning of the profile recording. End velocity: The profile recording stops when this velocity value has been reached. Start velocity and end velocity must not be equal. The range for each of the values is 2047.+2047. Pulse_Div: This is the pulse divisor of the TMC428 TMC428, that is a pre-divider that selects the velocity range (see the TMC428 TMC428 data sheet for explanation). It is set to 5 when the evaluation board is switched on, but it can be set to meet your needs here. Microsteps: The number of microsteps to be used can also be set here. The default value on the evaluation board is 16. After all these parameters have been set, click on the start button to start the StallGuard profile recording. Depending on the range between start and end velocity this can take several minutes, as the load value for every velocity value is measured ten times. The "Actual velocity" value shows the velocity that is currently being tested and so tells you the progress of the profile recording. You can also abort a profile recording by clicking the "Abort" button. Sternstraße 67 D - 20357 Hamburg, Germany Phone +49-40-51 48 06 - 0, FAX: +49-40-51 48 06 - 60 http://www.trinamic.com TMC428 TMC428 Evaluation Kit V3.0 15 5.3 The result The result is shown as a graphic at the right side of the programme window. After the profile recording has finished you can scroll through the profile graphic using the scroll bar below it. The scale on the vertical axis shows the load value: a higher value means a higher load. The scale on the horizontal axis is the velocity scale. The colour of each line shows the standard deviation of the ten load values that have been measured for the velocity at that point. This is an indicator for the vibration of the motor at the given velocity. There are three colours used: Green: The standard deviation is very low or zero. This means that there is effectively no vibration at this velocity. Yellow: This colour means that there might be some low vibration at this velocity. Red: The red colour means that there is high vibration at that velocity. Figure 5.2: A StallGuard profile The data can also be exported as a text file or to Microsoft Excel. To do this, click the "Export" button and a pop-up menu with the following choices appears: Text file: This function lets you choose a text file to which the data will be saved. Excel: This function exports the data to Microsoft Excel. It must be installed on your PC to make use of this function, as Excel is now started (if not already running) and the data is directly sent to Excel and not written into a file. Of course you can then save the data by using the save function in Excel. Please note that it takes some time to transfer the data to Excel. A profile that has been saved to a text file can be reloaded: just click the "Load" button and you can then select a file. The contents of the file will then be shown as a graphical profile. 5.4 Interpreting the result In order to make effective use of the StallGuard feature you should choose a velocity where the load value is as low as possible and where the colour is green. The very best velocity values are those where the load value is zero (areas that do not show any green, yellow or red line). Velocities shown in yellow can also be used, but with care as they might cause problems (maybe the motor stops even if it is not stalled). Velocities shown in red should not be chosen. Because of vibration the load value is often unpredictable and so not usable to produce good results when using stall detection. As it is very seldom that exactly the same result is produced when recording a profile with the same parameters a second time, always two or more profiles should be recorded and compared against each other.