Honeywell HMR4007 User's Manual
Contents
1. a Ber Board a KR ee oni port Sensor Board gt gt Z o o o i power i input 5 28VDC T I 1 1 RA3 Tak Gray 1 I status TTL output _ Logic 0 output not valid a Sees e WP _ yellow H E D Logic 1 output valid J ati ee ee eee A alog output 0 0 2 sv O O O ee i eS _ power ground _ SA 5 J Mec ES 28 VDC ed as i i i i power gnd black _ SJ fn URA ei L AT Sx status LPT port base address 1 Bit x M il mt Dx data LPT port base address 0 Bit x _ a I EANNAN EESE Figure 1 Sensor board layout and connector pin designations MATING PARTS Connectors J1 J2 and J3 mate with GC Waldom C Grid crimp style shells and terminals Polarized shells with a locking tab or unpolarized shells are available The applicable GC Waldom part numbers are Connector pins Polarized shell Unpolarized shell Crimp terminals J1 6 50 57 9406 50 57 9006 16 02 0097 50 57 9404 50 57 9004 16 02 0097 50 57 9404 50 57 9004 16 02 0097 Solid State Electronics Center www magneticsensors com 800 323 8295 Page 5 HMR4007 Honeywell SENSOR PRODUCTS APPLICATION NOTES USING THE HMR4007 AS A STAND ALONE SENSOR Introduction The HMR4007 can be used as a stand alone sensor without t2. The sensor is shipped with the axial mode selected Once set into an operating mode that mode is retained in nonvolatile RAM The functions EnableDAC and DisableDAC are used to enable and disable the digital to analog DAC output on port J2 The sensor is shipped with the DAC enabled Once set into an operating mode that mode is retained in nonvolatile RAM HMR4007 exe This is a simple Visual Basic 5 0 executable that demonstrates the use of the DLL and shows a simple graphical display of the current position Source code for the program is available and can be modified as desired The position window will turn yellow in the event of a communications failure or turn red in the event of a position error MAGNET CONSIDERATIONS The choice of magnet to be used with the HMR4007 is critical to its accuracy Because a magnet s field extends beyond the boundaries of the material a magnet has two dimensions to consider its physical material length and its apparent magnetic length The heart of the HMR4007 is Honeywell s HMR1501 magnetoresistive MR sensor that responds to the angle between the chips sensitive axis and the magnetic field The HMR1501 has a maximum response when this angle is 45 degrees We can therefore define the magnet s apparent length as the distance between the 45 and 45 degree points at the gap distance As the gap between the magnet and the sensor array increases the apparent length of the magnet increases as
3. the target magnet is highly variable A magnet of sufficient strength however must be used to maintain a magnetic field strength of 80 gauss min at the sensor array and an apparent magnet length of 23 mm Note 2 Sensor boards are factory calibrated in the axial mode using a 27mm cylindrical magnet Operation in the radial mode must be configured by the user Note 3 cf Magnet Considerations pg 8 Solid State Electronics Center www magneticsensors com 800 323 8295 Page 3 HMR4007 Honeywell SENSOR PRODUCTS PIN CONFIGURATION Pin Number Pin Name _ _ Description Digital Interface Serial Clock Output Data Out Serial Data Output Data_In Serial Data Input CTS Serial Clock Input 5 Power Unregulated Power Input 6 to 28 VDC see note 1 END Power and Signal Ground Analog Interface Power Unregulated Power Input 6 to 28 VDC see note 2 Analog Out 0 2 5 VDC analog output _ is Valid TTL level 0 Pen invalid 1 position valid Jumper Block 1 Analog Output port selected as power source Serial Communications port selected as power source Note 1 The board contains three interface connectors for digital and or analog communications Power is supplied to the board through any one of these connectors and is selected by jumper block 1 All of the ground connections on all three ports are common to the circuit ground and are not affected by the jumper position Only ONE o
4. well A general rule of thumb for a cylindrical bar magnet is that the apparent length will increase by the amount of the gap A twenty five millimeter long magnet for example will appear to be thirty five millimeters long at a gap of 10 millimeters Since magnetic fields are highly nonlinear and subject to the exact geometry and properties of the material this is only a general guide The HMR4007 uses three sensors in its array at all times in order to physical apparet calculate position It automatically selects the sensors closest to the lagh magnet for this purpose The apparent magnet length must therefore be greater than he spacing between three sensors and this distance is 23 2mm for the HMR4007 The disadvantage of increasing the gap between the sensor and magnet in order to increase its apparent length is that a magnet s field strength decreases exponentially with gap In order to maintain the MR sensor s response the magnetic field at the sensor must be greater than 35 gauss Unless extremely strong rare earth magnets are economically feasible or a large gap is required because of restrictions on where the magnet and array can be mounted it is usually better to keep the gap to a minimum and use a longer magnet gap Figure 3 Magnet apparent length 900301 01 03 Rev A Solid State Electronics Center www magneticsensors com 800 323 8295 Page 8
5. HMR4007 Honeywell SENSOR PRODUCTS HMR4007 Linear Position Sensor User s Guide nics Center www magneticsensors com 800 323 8295 Page 1 HMR4007 Honeywell SENSOR PRODUCTS INTRODUCTION The Honeywell HMR4007 is an electronic linear position sensing solution for use in commercial and industrial application environments A stationary array of Honeywell s magnetoresistive MR sensors is utilized to quickly and accurately monitor the position of a small magnet attached to a moving object such as a valve stem or hydraulic cylinder The use of a sensor array makes the solution highly insensitive to many environmental influences such as magnet strength alignment run out and temperature This solution is easily integrated into systems using a highly reliable serial interface or a 12 bit analog output with over range error indication In normal operation a small target magnet is mounted to the moving object whose position is to be monitored and the sensor array is held stationary The exact standoff distance gap is arbitrary between 1 2 to 1 1 2 as the embedded software is highly tolerant of this gap The sensed axis is parallel to the long axis of the sensor board The embedded software then calculates the position of the magnetic center of the target magnet as a function of its distance along the axis of the board The result is expressed as a 12 bit unsigned integer or as a 12 bit analog voltage In the example t
6. etween the sensor and magnet along the length of travel Status Pin Pin 2 on port J2 is a TIL logic level status output bit This pin will be logic high 5VDC whenever the position output is valid Logic level low ground indicates that the sensor cannot calculate a magnet position The most likely causes of a position error signal are 1 The magnet is beyond the sensed range of the device 2 The magnet is too short or too weak for the sensors to track 3 The gap between the sensor and magnet is too large 4 The magnet is not present Solid State Electronics Center www magneticsensors com 800 323 8295 Page 6 HMR4007 Honeywell SENSOR PRODUCTS USING THE HMR4007 IN DIGITAL COMMUNICATIONS MODE Introduction The HMR4007 is capable of communicating with a higher level system through a proprietary communications port J1 This port uses a bit clocked serial protocol for higher speed and higher data integrity than standard serial protocols Signal levels are standard TTL compatible For convenience a windows based DLL dynamic link library and sample Visual Basic demonstration program are available from Honeywell that communicates with the sensor through a PC s parallel port Interested developers should contact their Honeywell representatives or the factory for details of the communications protocol and command structure The communications port can be used independently or in combination with the analog output described earlie
7. f the three positions on JP1 should be shorted at a time Shorting more than one may result in excessive power supply currents and board damage CIRCUIT DESCRIPTION The HMR4007 Linear Position Sensor circuit board includes all of the basic sensors and electronics to provide a digital indication of position of a target magnet The HMR4007 starts with an array of seven Honeywell HMC1501 single axis magnetoresistive MR sensors to determine the field geometry and direction of a target magnet attached to the moving part of a device under test These sensors are supplied power by a constant voltage source and the use of an array of sensors helps to maintain accuracy over temperature and run out The sensor outputs are routed to a multiplexed Analog to Digital Converter ADC integrated circuit A microcontroller integrated circuit periodically queries the multiplexed ADC and performs sensor offset and gain corrections and computes the position of the target magnet as a function of the distance of travel along the long axis of the sensor board The position data along with an error bit is available thought the serial interface or is present on the Digital to Analog Converter DAC output port The serial interface is not needed in order to use the board s stand alone analog output The microcontroller also performs the external serial data interface and other housekeeping functions An onboard EEPROM integrated circuit is employed as a nonvolatile storage t
8. he need for any digital communications The board is configured at the factory to provide a 0 2 5 VDC analog output axial magnet and status signal that represents the position of the magnet along the long axis of the device All power and signals are available on connector J2 Connector J2 General Description When used in a stand along mode only connector J2 needs to be used Connector J2 is a 4 pin socket header that is used to supply power pin 1 ground pin 4 analog position pin 3 and status pin 2 When power is supplied to the board though J2 a jumper must be placed on pins 2 5 center pair in jumper block JP2 The power supply can be regulated 5VDC or unregulated 6 28VDC If connector J2 is used in combination with the communications port only ONE of the ports should be used to supply power to the board Analog Outputs The analog output J2 pin 3 represents the position of the magnet along the long axis of the sensor board as seen in Figure 2 below In the given example the center of the magnet lies between sensors 3 and 4 The resulting output voltage is 1 20 volts which corresponds to a position of 33 4 mm A 10n mm a posi Output volts DC Figure 2 Position sensing example An effort should be made to keep the angle of the magnet with respect to the sensor board reasonably constant along the length of travel The sensor however is quite tolerant to changes in distance gap b
9. nnnannnnnnannnnnnnunnnnannnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn Demonstration Software Two programs are included with this board to demonstrate its operation HMR4007 dIil is a dynamic link library that performs low level communications between the host PC s parallel port and the sensor board to query the current measured position and support operating mode changes Several functions are visible to the user using the following Visual Basic header formats Declare Function InitPort Lib HMR4007 dll ByVal ADD As Integer ByVal TOut As Long As Integer Declare Function CurrentPosition Lib HMR4007 dll As Integer Declare Function SetAxialMode Lib HMR4007 dll As Integer Declare Function SetRadialMode Lib HMR4007 dll As Integer Declare Function EnableDAC Lib HMR4007 dll As Integer Declare Function DisableDAC Lib HMR4007 dll As Integer The first function InitPort is used to setup the PC s parallel port base address default is 0x378 and timeout value This function must be called before any calls to the operating functions The port base address ADD is the address of the computer s parallel printer adapter and used by the software as a base address to send and receive data to the sensor card through the parallel port adapter The value is passed as a 16 bit integer Setting this value to 1 re initializes the port with the previous value or default value retained The timeout value Tout is used as an internal loop c
10. o retain necessary data and configuration variables for best performance The HMR4007 uses an on board low drop out LDO 5 volt regulator so that a regulated 5 volt power supply or an unregulated power supply in the range of 6VDC to 28VDC can be used The power is supplied to the board through one of the three user ports being serial analog or USB and a jumper is used to select which port is the power source Only one jumper should be in place at any one time as the board does not have over current protection and use of more than one jumper can result in excessive power supply currents and board damage Solid State Electronics Center www magneticsensors com 800 323 8295 Page 4 HMR4007 Honeywell SENSOR PRODUCTS PHYSICAL CHARACTERISTICS The circuit board for the HMR4007 Linear Position Sensor is approximately 340mm by 80mm A 6 pin right angle connector J1 and two 4 pin connectors J2 J3 protrude from the back of the board for user connections Components on the top side have a maximum height of 12mm Figure 1 shows a typical circuit board with dimensions PARTS PLACEMENT Not used leave all OPEN Where 1 J3 USB 2 J2 Analog output 3 J digital communications shown above Sensed axis M sl how IE M a ie o gt 5 4 40NF mounting holes L r Cy i connected to ground plane Rev i eo AE Bea E A 3200mi ooo ON vl _ USB port 118mi not used k k tA m m
11. o the left if the center of the magnet was aligned with the center of the bottom most sensor in the array the result would be interpreted as a position of O while stationary sensorcard alignment with the top most sensor would be interpreted as a position of 4095 To convert the reading to engineering units the reported position is divided by 4095 and then multiplied by the Pars span of the sensors 69 mm or 2 75 If we call the reported ky position x then the position in engineering units would be moving object Position in mm x 4095 69 6 Position in inches x 4095 2 75 The above example shows a magnet oriented in what is called the radial mode where the magnetic poles point towards the sensor card The embedded software is also capable of operating with a magnet oriented in the axial mode where the magnet poles point along the axis of the sensor as seen below The sensor card however does not automatically detect the magnet mode and a status bit in the embedded code must be set to configure the HMR4007 Software tools are available from Honeywell to easily accomplish this Radial mode magnet AxiaFmodemagnet The orientation of the north and south poles is arbitrary and the embedded software is highly tolerant of the magnet geometry so that rectangular bar magnets or cylindrical magnets can be used equally well Cylindrical magnets in the axial mode are partic
12. ounter to return to the calling program after a fixed time if for some reason the sensor board fails to respond A value of 10 000 is the default and works well on a 100MHz Pentium class machine Higher values will be needed for faster machines The parameter is passed as a 32 bit long integer Passing a value of 1 sets the value to the previous or default value The function returns a 16 bit integer 0 to indicate that the port is active Solid State Electronics Center www magneticsensors com 800 323 8295 Page 7 HMR4007 Honeywell SENSOR PRODUCTS The second function CurrentPosition is used to query the current position of the magnet The following 16 bit integer values are returned 0 1024 normal position response where 1024 represents full scale response 1 2 communications failure The sensor failed to respond to the PC quickly enough This is usually caused by improper wiring improper power settings a timeout value too small for the PC speed or the DLL not being initialized before attempting to get the position 3 position error The sensor communicated correctly but the sensor card was not able to calculate a valid position A position error is usually caused by the magnet being off the end of the board or not present The functions SetAxialMode and SetRadialMode are used to configure the sensor to use magnets in either the axial mode or radial see the introduction for a description of axial and radial modes
13. r When used in combination with the analog port only ONE port should be used to supply power to the board Sensor configuration such as changing the magnet mode from axial to radial is available only through the communications port and DDL calls are supplied to support these basic functions Connector J1 General Description J1 is a 6 pin header which is wired to a PC parallel port for digital communications with the Honeywell demonstration DLL software or other user application using the following connections S i prpin daia und e d i recti on P EEEE 15 lt 1 RTS gray vellou _ 3 TTE 3 bak blue E S N l S Cig BR whitey es nn a 25500 E a n ennenen ts 00 00 0551 S SENNA nanaanaaaananannanaannanannnnnnn anananannannnanannnnnnnnannnann
14. ularly attractive because the magnetic field is symmetrical with respect to rotation about the center axis without loss of position accuracy The magnet should have a minimum length of 23mm 0 91 inches along the axis of the travel Shorter magnets however can be used with some increase in the minimum gap between the magnet and sensor board as long as a minimum field strength of 80 gauss and an apparent magnet length of 23 mm is maintained at the sensor board More on apparent magnet length can be found in the application notes at the end of this document Solid State Electronics Center www magneticsensors com 800 323 8295 Page 2 HMR4007 Honeywell SENSOR PRODUCTS SPECIFICATIONS Characteristics Conditions Typ General Distance gap between the target magnet and the sensor board Magnetic Field Electrical Input Volage umregulated 6 20 a Digital Interface Baud Rate nonstandard synchronous serial interface 21 000 Signaling Level TTL levels 1 0 In Line 6 Pin Block 0 1 spacing Analog Interface Analog Output D A output Signaling Level TTL levels 1 VDC VDC VDC Hz VDC 0 VDC In Line 4 Pin Block 0 1 spacing SP Physical Dimensions Circuit Board Assembly 40 0 x 80 0 x including connectors 12 0 Weight HMR4007 Environment Temperature Operating 40 70 C Storage 55 125 Note 1 The standoff distance between the sensor board and
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