Sky Quality Meter – Lens USB SQMLU User manual
Contents
1. Microcontroller USB interface Illustration 1 SOM LU block diagram 1 1 Ouick start 1 Your computer must have the FTDI VCP driver installed You can get the most updated driver for your operating system from here http ftdichip com Drivers VCP htm 2 If you are using Windows then download and install the latest Knightware SOM Reader from www knightware biz sqm Follow the instructions for installing and using that software 3 If you are using Windows Linux or Mac you can use the Perl scripts supplied on the CD Revision 1 1 Page 3 Last modified Jun 18 2011 Unihedron SOM LU Users manual 2 Specifications USB connection USB B connector 5m USB A to USB B cable supplied USB FTDI VCP driver serial port emulator at 115200baud Physical Size 3 6 x 2 6 x 1 1 Meter precision Each SOM L is factory calibrated The absolute precision of each meter is believed to be 10 0 10 mag arcsec The difference in zeropoint between each calibrated SOM L is typically 10 0 10 mag sg arcsec Power reguirement 18mA from the 5V USB connection Operating temperature range 40 C to 85 C Temperature Accuracy 2 C maximum at 25 C Temperature update rate 4 3 seconds 256 samples taken at 60Hz then averaged m As Unihedron SQM LU Unihedron Illustration 2 Front and back of unit Revision 1 1 Page 4 Last modified Jun 18 2012. Revision 1 1 Page 6 Last modified Jun 18 2011 Unihedron SOM LU Users manual rx Reading request CX Calibration information request ix Unit information request note lower case 1 zcalAx Arm Light Calibration command zcalBx Arm Dark Calibration command zcalDx Disarm Calibration command zcal5 Manually Set Light Calibration Offset HHEX zcalo Manually Set Light Calibration Temperature HHEX zCal7 Manually Set Dark Calibration Time Period HHEX zCcal8 Manually Set Dark Calibration Temperature HHEX 0x19 Reset microcontroller see bootloader Hexadecimal value 19 Intel Hex firmware upgrade initiation see bootloader PHH HH H EX Set period in seconds for interval reporting to EEPROM and RAM for booting and immediate use Firmware feature 13 P HH H x Set period in seconds for interval reporting to RAM for immediate use Firmware feature 13 T HHHHHX Set threshold in mag arcsec for interval reporting only to EEPROM and RAM for booting and immediate use Firmware feature 13 t H HHHEHEAEX Set threshold in mag arcsec for interval reporting only to RAM for immediate use Firmware feature 13 Ix Request interval settings note upper case T Firmware feature 13 Table 1 Command summary Revision 1 1 Page 7 Last modified Jun 18 2011 Unihedron SOM LU Users manual 4 2 Response detail
3. own here http unihedron com projects sgmhousing Illustration 3 Housing 6 1 Cover selection If the unit is to be mounted in exposed location we recommend an acrylic dome Acrylic domes will last 2 3 years but eventually weather on the surface It is not clear that this will affect the reading much The best test would be to swap a weathered and new one back and forth when changing one out Presumably the main consideration would be to keep the domes clean every so often and to make sure that the mounting plane is painted black to that it doesn t reflect light back to the inside of the dome and then back into the meter Source of Acrylic domes http www globalplastics ca domes htm 6 2 Cover calibration Since the SQM LU is not weather proof it must be protected in some way from the elements A plastic dome is recommended This may reduce the incoming light by about 15 20 Because a covering will reduce the incoming light the resultant reading will be darker higher magnitudes per arcsecond value The offset determined by a simple light experiment should be subtracted from the reading A pending firmware edition will allow for built in manual offset Apply this subtraction offset as a negative value i e if you measured 16 60 outside the covering then 16 75 under the dome then an Revision 1 1 Page 21 Last modified Jun 18 2011 Unihedron SOM LU Users manual offset of 0 15 should be applied to all readin
4. revision history 1 0 Initial product release 1 1 Troubleshooting d specification addition 11 2 Protocol revision history 3 Initial SOM LE product release 4 Interval report reading includes serial number at end SOM LE 11 3 Feature revision history 9 Initial SOM LE product release 10 Power up default reset for command busy SOM LE 11 Ability to manually sett calibration values SOM LE 12 Temperature averaging added SOM LE 13 Interval report feature added SOM LE 14 Interval report includes serial number Revision 1 1 Page 28 Last modified Jun 18 2011
5. 1 Unihedron SOM LU Users manual 3 Hardware connections The SOM LU reguires one connection to a USB hub or a PC The maximum length cable per the USB specification is 15ft 3 meters 2 Software development The SOM LU communicates as a standard serial port device using the FTDI software drivers which are available for all major operating system platforms http ftdichip com The SOM LU uses the FTDI FT232R chip Once the driver is installed commands can be sent to the SOM LU using a serial terminal emulator to the serial communications port that the device routes to When connecting the SOM LU to a PC where the FTDI device driver is loaded the serial port label will be determined at connection time Each SOM LU has a unique serial number usually with a prefix of FT This serial number can be used to identify the exact SOM LU device from other USB devices Interface Program overview Data commands are sent to the SQM LU and it responds with a string of characters A connection must be made to the serial port assigned to the SOM LU Revision 1 1 Page 5 Last modified Jun 18 2011 Unihedron SOM LU Users manual 4 Commands and responses The SOM LU accepts a seguence of characters as a command then executes those commands and usually provides a response of a seguence of characters 4 1 Commands Commands consist of a string of characters The first character is the command type
6. Sky Quality Meter Lens USB SQM LU User manual Unihedron SOM LU Users manual Table of Contents LATER o PSRAILO O 3 IOM 00 ET a Cran eet er a des ada dos aa Ha STATEN Te reo KITT ales la oa to 3 DPIC TEC HIOIN naa sas MAITA dace asta S dente a Gade eater Ay ocala yn ductile dna mn OU heat vised ele ead eal Aaa 4 S aL OW abe ONMOCCH OU Senses itesto gs center ee O ns ses E celta madalsi 5 ZION Ware development in trsne ea in tomes 5 4 Commands ANA ESPOSA aka assi kt odo ma sas 6 A sristi e Gadel conte ottaa abla it eserita iega 6 42 Response detall Sor ma sa A caadon a e SSK E R 7 A A E is EE se fake T E EE E E Sn each 7 4 22 Calibrationiniormation FEQUCS cita 8 42 3 Light calibration command sree nr a ses vats ccc sence a i 9 4 24 Dark calibration COM lil 10 42 5 DIS atti calibration commandi yuslvy sich A E E 11 42 6 Unit inform tion sssrinin A TE OAE T ih 12 4 2 7 Manually set light calibration OffSet sc c sccasssecciaccessccessssavessacessaectsussenensadseatecestectbaneccdeanceoes 13 4 2 8 Manually set light calibration teMperature ooooonnccccnnocononocononoccnnnnncnnnnnconnnncnononcnnnnncnnncnnnnnnno 14 4 2 9 Manually set dark calibration time PerlOd oooococnnococnoncccnoncnononcnononanononccononcnnonnn conca connnccnnnos 15 4 2 10 Manually set dark calibration temperature s ooosossss osa aa n aan naa e aan an aeen 16 4 2 11 Setting interval reporting Parameters ini oogmeaedivendovesoeaeesdespa
7. all data about the specific light sensor in the unit reguired for to calculate a reading The format of the response is 0 C Indicates that the calibration information is being returned 2 13 00000017 60m Light calibration offset in magnitudes per square arc second 15 26 10000000 000s Dark calibration time period in seconds with millisecond resolution 28 34 039 4C Temperature in degrees C measured during light calibration Leading space for positive value Leading negative sign for negative value 36 47 00000008 71m Offset of light sensor based on manufacturing category 49 55 039 4C Temperature in degrees C measured during dark calibration Leading space for positive value Leading negative sign for negative value 56 57 Carriage return 0x0d Line feed 0x0a Table 3 Calibration information request response An example is c 00000017 60m 0000000 000s 039 4C 00000008 71m 039 4C 0123456789 123456789 123456789 123456789 123456789 1234567 Revision 1 1 Page 9 Last modified Jun 18 2011 Unihedron SOM LU Users manual 4 2 3 Light calibration command Calibration of the SOM LU is done at the factory in a controlled light and temperature environment Executing the Light calibration command zcalAx arms the light calibration mode Flipping the switch to unlock triggers the light calibration and modifies the calibration values in the unit A calibrated li
8. cancoeesee 17 4 2 11 1 Interval reporting period o PA A E 18 4 2 11 2 Threshold setting for interval Tp it 18 42 113 teryal setting response nei ie a e A A A EAA EAE 19 SIC GMICAl COMME CON asi a5 en e A 20 6 M chanical installato ii lina 20 A A Sauda a Esta tamas e KS Ss o ETS td ound eae tee Oe Taa ata eee 20 62 COVercalbraO arts dr 20 e ni AAA ak a Mi nese oan gk RD sit cot MAA mk it 21 TDS UE SUIS anna A Tn NN CA aseinaan 22 E E 23 Company SON TAO ITON A o O Sse a ea bn Ae saan 24 O 25 11 Appendix A revision history sia ici dai ridad sete e MIR dias netas 26 11 1 Manual revision history nin diaria 26 11 2 Protocol revision Dist airada sk ie iaai 26 11 3 Feature revision history ir rare 26 Revision 1 1 Page 1 Last modified Jun 18 2011 Unihedron SOM LU Users manual Illustration Index Illustration 1 SOM EU block Cider anit iS IAS 3 Tlustration 2 gt Front and back Of Unitas neck oe cee A eee aia ee a 4 SEA TON 3 HOUSING vessa Sa massat Sap os genes o a a is 20 Illustration 4 Example cover cabros dis 21 Index of Tables Table T Command SUMAN idas 6 Table 2 RACINE TEESE TES PA o o es do 7 Table 3 Calibration information request responsa 8 T ble 4 Light calibration response enion A ES 9 Table 5 Dark calibration TES PON ii andas 10 Table 6 Disarm calibration TeSPOnse v ussiaavstaa va ma vasaa sana den a v est avan T Sadan ena aas es decidida decantan 11 Table 7 Unit information request re
9. ch interval report is the same as the reading reguest report except that the serial number feature 14 and above is attached at the end so that numerous reporting SOM LUs can be distinguished from each other The format of the interval report is 0 r Indicates that a reading is being returned 2 8 06 70m Reading in magnitudes per sguare arc second Leading space for positive value Leading negative sign for negative value A reading of 0 00m means that the light at the sensor has reached the upper brightness limit of the unit 10 21 0000022921Hz Frequency of sensor in Hz 23 33 Q000000020Cc Period of sensor in counts counts occur at a rate of 460 8 kHz 14 7456MH7z 32 35 46 0000000 000s Period of sensor in seconds with millisecond resolution 48 54 039 4C Temperature measured at light sensor in degrees C Leading space for positive value Leading negative sign for negative value 55 63 00000413 Serial number 8 digits Each unit has its own unigue serial number 64 65 Carriage return 0x0d Line feed 0x0a Table 12 Interval report An example is r 06 70m 0000022921Hz 0000000020c 0000000 000s 039 4C 00000413 0123456789 123456789 123456789 123456789 123456789 123456789 12345 Revision 1 1 Page 18 Last modified Jun 18 2011 Unihedron SOM LU Users manual Interval reporting is available for sending timed reports to a listening program To prevent rep
10. diately after Arm command Enable firmware upgrade 4 5 Carriage return 0x0d Line feed 0x0a Table 5 Dark calibration response An example is zBaL 012345 Revision 1 1 Page 11 Last modified Jun 18 2011 Unihedron SOM LU Users manual 4 2 5 Disarm calibration command The Disarm calibration command zca1Dx disarms calibration modes from being triggered by the unlock mode The format of the response is 0 Z Calibration response is being returned 1 X All calibration modes 2 d Disarmed 3 E L Locked Wait for unlock before calibrating after Arm command firmware upgrades are disabled U Unlocked Calibrate immediately after Arm command Enable firmware upgrade 4 5 Carriage return 0x0d Line feed 0x0a Table 6 Disarm calibration response An example is zxdl 012345 Revision 1 1 Page 12 Last modified Jun 18 2011 Unihedron SOM LU Users manual 4 2 6 Unit information Unit information command ix provides details about the software in the microcontroller The format of the response is 0 i Indicates that the unit information response is being returned 2 9 00000002 Protocol number 8 digits This will always be the first 8 characters after the i response This value indicates the revision number of the data protocol to from the SQM LU The protocol version is independent of the featu
11. e lower case t sets the threshold of the timed interval reports to RAM for immediate use only magnitudes arcsecond magnitudes arcsecond The units are For example t 00000016 00x limits reporting to values only over 16 00 Revision 1 1 Page 19 Last modified Jun 18 2011 Unihedron SOM LU Users manual 4 2 11 3 Interval setting response Either making the request Ix note upper case T or any request to set the interval report setting produces the following response 0 I Interval settings from EEPROM and RAM are being returned 2 12 0000000360s Interval period that was set into EEPROM 14 24 00003003605 Interval period that was set into RAM 26 37 00000017 60m Threshold value that was set into EEPROM 39 50 00000017 60m Threshold value that was set into RAM 51 52 Carriage return 0x0d Line feed 0x0a Table 13 Response of viewing or setting interval reporting parameters An example response is I 0000000360s 0000000360s 00000017 60m 00000017 60m Revision 1 1 Page 20 Last modified Jun 18 2011 Unihedron SOM LU Users manual 5 Electrical connection The SOM LU uses a voltage regulator to bring the incoming USB SVDC voltage down to 3 3VDC 6 Mechanical installation Unihedron sells an enclosure that is suitable for mounting either the SOM LE or SOM LU into You can read more about it including plans to build your
12. f the SOM LU is plugged in the active COM port will show up in this list HK LOCAL MACHINEY HARDWARE DEVICEMAP SERIALCOMM For Linux and Mac use 1sha1 to determine which device the FTDI driver has attached the SOM LU to The CD contains a Perl script findftdi pl to filter out the Ishal output Revision 1 1 Page 24 Last modified Jun 18 2011 Unihedron SOM LU Users manual Revision 1 1 Page 25 Last modified Jun 18 2011 Unihedron SOM LU Users manual 9 Company contact information Mailing address Unihedron 4 Lawrence Avenue Grimsby Ontario L3M 2L9 Canada Telephone 905 945 1197 Fax 905 945 6770 Website unihedron com Email info unihedron com Revision 1 1 Page 26 Last modified Jun 18 2011 Unihedron SOM LU Users manual 10 Glossary EEPROM Electrically Erasable Programmable Read Only Memory is a type of memory that retains its contents after the power has been removed This type of memory has a limited write erase cycle as well as a lifetime for data retention In the SOM LU the parameters in the micro controller can be written 1 million times and last for 100 years SOM LU Sky Ouality Meter with lens and USB connectivity USB Universal Serial Bus Revision 1 1 Page 27 Last modified Jun 18 2011 Unihedron SOM LU Users manual 11 Appendix A revision history 11 1 Manual
13. ght source of approximately 13 5fc is supplied to the sensor The format of the response is 0 Z Indicates that a Calibration response is being returned A Light Calibration 2 a armed 3 L L Locked Wait for unlock before calibrating after Arm command firmware upgrades are disabled U Unlocked Calibrate immediately after Arm command Enable firmware upgrade 4 5 Carriage return 0x0d Line feed 0x0a Table 4 Light calibration response An example is zAaL 012345 Revision 1 1 Page 10 Last modified Jun 18 2011 Unihedron SOM LU Users manual 4 2 4 Dark calibration command Dark Calibration is done at the factory along with Light calibration and calibration temperature recording Executing the dark calibration command zca1Bx arms the dark calibration mode Flipping the switch triggers the dark calibration and modifies the calibration values in the unit Dark calibration is performed in a completely dark environment Check a reading to ensure that the period is correct after entering the dark environment it could take a few minutes to collect an accurate dark period A dark period of only a few seconds is too small The format of the response is 0 Z Calibration response is being returned 1 B Dark Calibration 2 a Armed 3 L L Locked Wait for unlock before calibrating after Arm command firmware upgrades are disabled U Unlocked Calibrate imme
14. gs Uniform lighting condition Ce Weatherproof covering SQM LE Offset 16 75 16 60 0 15 Illustration 4 Example cover calibration 6 3 Cover maintenance Keep the covering clean of dust water ice and bird droppings Revision 1 1 Page 22 Last modified Jun 18 2011 Unihedron SOM LU Users manual 7 Default settings The FTDI interface has not been altered from its default There should be no reason to alter the FTDI chip settings The baud rate is defined by the VCP driver side when a terminal program connects to the SOM LU Revision 1 1 Page 23 Last modified Jun 18 2011 Unihedron SOM LU Users manual 8 Troubleshooting Reading too bright too hot inspect lens for IR filter Problem Cannot get a reading Cause Driver is not installed or the SOM LU is not connected Solution For Windows check that the unit is registered using the registry editor from the Start menu select Run then type in regedit and press OK For Windows XP and Windows 2000 look here for your device HKEY LOCAL MACHINFEY SYSTEM Enum FTDIBUS VID_0403 PID_6001 Serial_Number 00001 PortName For Windows 98 and Windows ME look here for your device HKEY LOCAL MACHINFY SYSTEM Enum FTDIBUS VID_0403 PID_6001 Serial_Number 00001 PortName The Serial Number is printed on the bottom of the unit The above will identify which COM port the SOM LU has been assigned I
15. ibration Offset 4 15 0000300 000s Value that was set into EEPROM 16 17 Carriage return 0x0d Line feed 0x0a Table 10 Response of manually setting dark calibration time period An example is z 7 00000300 00s Revision 1 1 Page 16 Last modified Jun 18 2011 Unihedron SOM LU Users manual 4 2 10 Manually set dark calibration temperature Calibration is done at the factory however in the case where calibration values must be restored or set to something else this command allows a new calibration value to be placed into the SOM LU Executing the command zcal8 x manually sets the light calibration offset to the value specified in The units are C Note The SQM LU records the temperature in a raw value with different resolution so the reply back may not be exactly the same as the value sent The format of the response is 0 Z Calibration response is being returned 8 Manual Set Light Calibration Offset 4 9 019 0C Value that was set into EEPROM 10 11 Carriage return 0x0d Line feed 0x0a Table 11 Response for manually setting of light calibration temperature An example is z 8 019 0C Revision 1 1 Page 17 Last modified Jun 18 2011 Unihedron SOM LU Users manual 4 2 11 Setting interval reporting parameters For firmware feature 13 and above the SOM LU is capable sending timed interval reports Ea
16. orts being sent during daylight when the meter is saturated with light a threshold value can be set Readings exceeding the threshold dark will be reported low readings too bright will be suppressed Due to the construction nature of EEPROM there is a limited number of times that this memory can be written to before it becomes unreliable In the case of the SOM LU the erase write cycle is 1 million times For this reason it is recommended that freguent parameter changes be done in RAM rather than in EPROM Only set the parameter to EEPROM when you want the unit to boot up with your setting See following sections for how to set EEPROM or RAM Loading firmware clears resets the micro controller effectively copying the EEPROM values into RAM 4 2 11 1 Interval reporting period setting Executing the command P X note upper case P sets the period of the timed interval reports to the EEPROM and RAM for booting and immediate use Executing the command p xX note lower case p sets the period of the timed interval reports to RAM only for immediate use The units are seconds For example p0000000360x sets the reporting time to once every 360 seconds 4 2 11 2 Threshold setting for interval reporting Executing the command T i X note upper case T sets the threshold of the timed interval reports to EEPROM and RAM for boot and immediate use Executing the command t i x not
17. re version 11 18 00000003 Model number 8 digits The model value identifies the specific hardware model that the firmware is tailored for 20 27 00000001 Feature number 8 digits The feature value identifies software features independent of the data protocol 29 36 00000413 Serial number 8 digits Each unit has its own unique serial number 37 38 Carriage return 0x0d Line feed 0x0a Table 7 Unit information request response An example is i 00000002 00000003 00000001 00000413 Revision 1 1 Page 13 Last modified Jun 18 2011 Unihedron SOM LU Users manual 4 2 7 Manually set light calibration offset Calibration is done at the factory however in the case where calibration values must be restored or set to something else this command allows a new calibration value to be placed into the SOM LU Executing the command zcal5 x manually sets the light calibration offset to the A hein ay CO arcsecond The format of the response is 0 Z Calibration response is being returned 5 Manual Set Light Calibration Offset 4 15 00000017 60m Value that was set into EEPROM 16 17 Carriage return 0x0d Line feed 0x0a Table 8 Response for manual setting of light calibration offset An example is Z 5 00000017 60m Revision 1 1 Page 14 Last modified Jun 18 2011 Unihedron SOM LU Users manual 4 2 8 Manually set light calibra
18. s 4 2 1 Reading reguest The Reading request rx commands the SOM LU to provide the current darkness value as well as all variables used to generate that result The format of the response is 0 r Indicates that a reading is being returned 2 8 06 70m Reading in magnitudes per square arc second Leading space for positive value Leading negative sign for negative value A reading of 00m means that the light at the sensor has reached the upper brightness limit of the unit 10 21 0000022921HZ Frequency of sensor in Hz 23 33 Q000000020Cc Period of sensor in counts counts occur at a rate of 460 8 kHz 14 7456MH7z 32 35 46 0000000 000s Period of sensor in seconds with millisecond resolution 48 54 039 4C Temperature measured at light sensor in degrees C Leading space for positive value Leading negative sign for negative value 55 56 Carriage return 0x0d Line feed 0x0a Table 2 Reading request response An example is r 06 70m 0000022921Hz 0000000020c 0000000 000s 039 4C 0123456789 123456789 123456789 123456789 123456789 123456 Future revisions of this reading string will only modify reported values beyond position 54 Characters 0 to 54 may be considered stable Revision 1 1 Page 8 Last modified Jun 18 2011 Unihedron SOM LU Users manual 4 2 2 Calibration information reguest The calibration information request cx returns
19. sponse uousussss eaa aa e aa eaa enaa a naa a naan naa a naa nan naaeen 12 Table 8 Response for manual setting of light calibration offset uuuoosssn eaa n a a naene naene 13 Table 9 Response for manually setting of light calibration teMperature oooconnnoccconcccnooncnononacinnnccnannnnnns 14 Table 10 Response of manually setting dark calibration time periOd eee eee eeteceseeeeeeeeaeecneeeneeeees 15 Table 11 Response for manually setting of light calibration temperature ouossssn naene 16 Table 12 Interval keDOrk ssanmassi saak MIS ET o ea diese 17 Table 13 Response of viewing or setting interval reporting parameterS oococnnococnoncccnonccononcnononccnnnnncnnnos 19 Revision 1 1 Page 2 Last modified Jun 18 2011 Unihedron SOM LU Users manual 1 Theory of operation The SOM LU measures the darkness of the night sky to provide readings of magnitudes per sguare arc second through a USB connection A light sensor TSL237 provides the microcontroller with a light level and readings from the temperature sensor are used to compensate the light sensor readings for various operating temperatures Commands sent from a PC through the USB cable to the USB interface are relayed to the microcontroller The microcontroller responds to commands by sending data strings to the USB interface which are then relayed to the PC Light sensor Temperature sensor Data Power
20. tion temperature Calibration is done at the factory however in the case where calibration values must be restored or set to something else this command allows a new calibration value to be placed into the SOM LU Executing the command zcalo t x manually sets the light calibration temperature to the value specified in The units are C Note The SOM LU records the temperature in a raw value with different resolution so the reply back may not be exactly the same as the value sent The format of the response is 0 Z Calibration response is being returned 6 Manual Set Light Calibration Offset 4 9 019 0C Value that was set into EEPROM 10 11 Carriage return 0x0d Line feed 0x0a Table 9 Response for manually setting of light calibration temperature An example is z 6 019 0C Revision 1 1 Page 15 Last modified Jun 18 2011 Unihedron SOM LU Users manual 4 2 9 Manually set dark calibration time period Calibration is done at the factory however in the case where calibration values must be restored or set to something else this command allows a new calibration value to be placed into the SOM LU Executing the command zcal7 x manually sets the light calibration offset to the value specified in di The units are in seconds The format of the response is 0 Z Calibration response is being returned 7 Manual Set Light Cal
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