Digital Thermometer Thermostat with RS-485 Interface Model 485DTT

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Digital Thermometer Thermostat with RS-485 Interface Model 485DTT

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Digital Thermometer Thermostat with RS-485 Interface
Model 485DTT
Documentation Number 485DTT1795
This product
Designed Manufactured Ottawa, Illinois
domestic imported parts
Electronics Mfg. Inc.
Dayton Road P.O. 1040 Ottawa, 61350 (815) 433-5100 (815) 433-5105
Internet: http://www.bb-elec.com orders@bb-elec.com support@bb.elec.com
Electronics April 1995
Documentation Number 485DTT1795 Manual Cover Page Electronics 1040 Ottawa, 61350 (815) 433-5100 (815) 433-5105
Table Contents
CHAPTER GENERAL INFORMATION INTRODUCTION FEATURES PACKING LIST SPECIFICATIONS CHAPTER 485DTT FUNCTIONS.3 DIGITAL THERMOMETER PROGRAMMABLE THERMOSTAT.3 CHAPTER 485DTT DATA FORMAT CHAPTER 485DTT COMMANDS.7 READ TEMPERATURE READ STATUS READ HIGH READ CLEAR STATUS REGISTER HIGH THERMOSTAT.9 THERMOSTAT ADDRESS TURN AROUND DELAY CHAPTER CONNECTING 485DTT POWER CONNECTIONS RS-485 LINE TERMINATION.11 MULTIDROP APPLICATIONS CHAPTER SOFTWARE INSTALLATION WINDOWS SETUP APPENDIX USING SIMPTERM.15 APPENDIX DECIMAL/ASCII TABLE.17
Documentation Number 485DTT1795 Manual Table Contents Electronics 1040 Ottawa, 61350 (815) 433-5100 (815) 433-5105
Chapter General Information
Introduction 485DTT digital thermometer thermostat which operates through RS-485 interface. Non-volatile registers hold programmable high thermostat settings. Current temperature reported polling DTT, while thermostat operations continue long unit powered. RS-485 interface allows multiple units communicate 4000 feet single pair wires. Features ±0.5 accuracy resolution High, hysteresis type thermostat outputs Thermostat thresholds programmable non-volatile registers Status Register latches thermostat outputs have tripped Programmable node address turn around delay
Packing List Examine shipping carton contents physical damage. following items should shipping carton: 485DTT unit 485DTT 3.5" disk This instruction manual these items damage missing, contact Electronics immediately.
Documentation Number 485DTT1795 Manual Chapter Electronics 1040 Ottawa, 61350 (815) 433-5100 (815) 433-5105
Specifications Communications: Standard: RS-485 four-wire Baud Rate: 1200 9600 (automatic detection) Format: data bits, stop bit, parity Connector: DB-25S (female), RS-530 pinouts Optical Isolation: optical isolation required, B&B's 485HSPR high-speed optically isolated converter with this product. Thermometer Error ±0.5 from (±0.9 from 158°F) from (±1.8 from 485DTT guaranteed operate from 0-70 Thermometer Resolution (0.9 Temperature Conversion Time second Open Collector Thermostat Outputs (on) voltages: 1.2VDC High (off) voltages: 40VDC Power Supply External power: 12VDC 25mA
Chapter Documentation Number 485DTT1795 Manual Electronics 1040 Ottawa, 61350 (815) 433-5100 (815) 433-5105
Chapter 485DTT Functions
Digital Thermometer 485DTT continuously measures temperature, with measurement completed once second. When Read Temperature command received, immediately reports back result last measurement completed. Programmable Thermostat 485DTT also functions thermostat. nonvolatile registers programmed. high threshold register, programmed using !0SH command. threshold register, programmed using !0SL command. Chapter describes 485DTT commands. Thermostat operation continuous background function. long unit powered, thermostat outputs will serviced. Three open collector outputs provide thermostatic controls. These outputs current sinking (low) when high impedance (high) when off. THIGH Turns when temperature equals exceeds user programmed register TLOW Turns when temperature equal less than user programmed register TCOM Turns when temperature equals exceeds register turns when temperature equal less than register. This output allows user program amount hysteresis. Remember, these open collector outputs. They source current (similar contact closure ground). example, drive relay with 12VDC coil with TCOM output, connect follows: Connect +12Vdc side relay coil. Connect other side coil TCOM output. Connect ground supply terminal block.
Documentation Number 485DTT1795 Manual Chapter Electronics 1040 Ottawa, 61350 (815) 433-5100 (815) 433-5105
+12VDC
12VDC RELAY COIL
RELAY CONTACT
OUTPUT
TCOM
Figure Relay Output Connection When connecting mechanical relay coil, inductive load outputs, reverse bias diode must connected across load protect output against large voltages caused inductive load. NOTE: outputs handle maximum voltage maximum current 100mA. relay with coil ratings exceeding these values.
Chapter Documentation Number 485DTT1795 Manual Electronics 1040 Ottawa, 61350 (815) 433-5100 (815) 433-5105
Chapter 485DTT Data Format
uses 9-bit, two's complement format represent temperature data. ninth sign bit. this temperature above temperature less than Each represents Table Temperature/Data Relationships Temperature output value value 11111010 +125 00110010 00000001 00000000 11111111 -1/2 11001110 10010010
Two's complement format provides digital devices handle negative numbers. convert two's complement value meaningful number representing temperature, follow these steps: Check nine. case this entire first character. character decimal (NUL), then value second character positive further complementing necessary, step character decimal then proceed step function your programming language invert complement) value second character. need insure that only dealing with eight variable. able define this your programming language. sure, function limit value only eight bits ANDing value from step with FFh. This masks lowest eight bits. value from step This completes two's complement portion conversion. Multiply value This simply adds sign temperature reading.
Documentation Number 485DTT1795 Manual Chapter Electronics 1040 Ottawa, 61350 (815) 433-5100 (815) 433-5105
convert Celsius, divide two. convert Fahrenheit, multiply Celsius value divide result then BASIC language, these steps look like this: `DTT data been stored CHAR1$ CHAR2$ negative ASC(CHAR1$) `ASCII sign char reading ASC(CHAR2$) `ASCII reading negative THEN reading reading `invert bits (complement) reading reading &HFF `limit variable bits reading reading `finish complement procedure reading reading `multiply minus sign Ctemp reading Ftemp Ctemp `Celsius temperature `Fahrenheit temperature
Chapter Documentation Number 485DTT1795 Manual Electronics 1040 Ottawa, 61350 (815) 433-5100 (815) 433-5105
Chapter 485DTT Commands
commands issued from program, even typed from simple terminal program. files included 485DTT disk help learn commands. sample program with source code written QuickBASIC demonstrates functions. simple terminal program from which manually communicate with 485DTT also included. Appendix demonstrates communicate with from terminal program. decimal/ASCII conversion table included Appendix 485DTT commands prefixed character. second character programmable address character factory preset (ascii zero). simplicity, address character assumed throughout this section. 485DTT been programmed different address, replace with address character. Read Temperature Command: !0RT Arguments: none Response: temperature reading two's complement format (shown boldface) Dec. Example: !0RT<0><46> ASCII Example: !0RT<NUL>. Description: decimal (NUL) followed decimal equivalent ASCII converts temperature Read Status Command: !0RS Arguments: none Response: contents status register (shown boldface) Dec. Example: !0RS<0><66> ASCII Example: !0RS<NUL>B Hex. Example: !0RS<0><42> (since this eight register, helpful representation) Description: first character (NUL) meaning this response. second character defines status. second character set, indicating normal operation. clear indicating thermostat tripped. set, indicating THIGH tripped since last !0SC command.
Documentation Number 485DTT1795 Manual Chapter Electronics 1040 Ottawa, 61350 (815) 433-5100 (815) 433-5105
Table Status Register Description (don't care) operation Thermostat Tripped Flag High Thermostat Tripped Flag Read High Command: !0RH Arguments: none Response: contents register two's complement format (shown boldface) Dec. Example: !0RH<0><50> ASCII Example: !0RH<NUL>2 Description: register contains decimal (ASCII NUL) decimal (ASCII This converts temperature When current temperature high thermostat output (THIGH) will turn Read Command: !0RL Arguments: none Response: contents register two's complement format (response shown boldface) Dec. Example: !0RL<0><36> ASCII Example: !0RL<NUL>$ Description: register contains decimal (ASCII NUL) decimal (ASCII This converts temperature When current temperature thermostat output (TLOW) will turn Clear Status Register Command: !0SC Arguments: none Response: none Example: !0SC Description: Clear Status command resets DTT. Bits which latch thermostat outputs cleared current temperature within bounds
Chapter Documentation Number 485DTT1795 Manual Electronics 1040 Ottawa, 61350 (815) 433-5100 (815) 433-5105
High Thermostat Command: !0SH Arguments: bit, two's complement value non-volatile register. Response: none Dec. Example: !0SH<0><64> ASCII Example: !0SH<NUL>@ Description: Sending decimal arguments (ASCII NUL) (ASCII sets register temperature This non-volatile register will change until this command issued again. After sending High Thermostat command, delay least allow program register. Thermostat Command: !0SL Arguments: bit, two's complement value non-volatile register. Response: none Dec. Example: !0SL<0><33> ASCII Example: !0SL<NUL Description: Sending decimal arguments (ASCII NUL) (ASCII sets register temperature 16.5 This non-volatile register will change until this command issued again. After sending Thermostat command, delay least allow program register. Address Command: !0SA Arguments: eight character. This character will replace current address character. address character must between decimal 255. Response: none Dec. Example: !0SA<53> ASCII Example: !0SA5 Description: Sending decimal arguments (ASCII will reprogram address character "5". This address nonvolatile only changed with Address command (i.e. !5SA0 change address back "0"). utility FINDER.EXE included 485DTT disk will scan addresses locate "lost" modules.
Documentation Number 485DTT1795 Manual Chapter Electronics 1040 Ottawa, 61350 (815) 433-5100 (815) 433-5105
Turn Around Delay Command: !0SD Arguments: eight character. RS-485 turn around delay (delay between receiving command sending response) multiple character length current baud rate. Turn around delay values must range from decimal 255. Response: none Dec. Example: !0SD<5> ASCII Example: !0SD<ENQ> Description: Sending decimal argument (ASCII ENQ) will reprogram turn around delay character lengths. 9600 baud this would 5ms, 1200 baud would 40ms. This setting non-volatile only changed with Turn around Delay command. Turn around delay character factory. Table Command Summary Function Command Argument read temperature !0RT none read status register !0RS none read high thermostat !0RH none read thermostat !0RL none clear status register !0SC none high thermostat* !0SH bit, comp. thermostat* !0SL bit, comp. address* !0SA address char byte) turn around !0SD number chars delay* delay byte)
Return Value bit, comp. byte bit, comp. bit, comp. none none none none none
*NOTE: After "programming" 485DTT, there approximately 10ms down time when unit will respond. attempt communicate with least 10ms after programming thermostat registers, address character turn around delay.
Chapter Documentation Number 485DTT1795 Manual Electronics 1040 Ottawa, 61350 (815) 433-5100 (815) 433-5105
Chapter Connecting 485DTT
485DTT serial connections made DB25 female connector. General information RS-485 found Electronics' free RS-422/RS-485 Application Note. Table 485DTT Pinouts Signal TD(A) TD(B) RD(A) RD(B) Power Connections reduce power consumption (and heat production) 485DTT, care should taken keep external supply close 12VDC possible. Higher levels will create additional unwanted heat unit. Unavoidably, some power dissipated 485DTT, producing heat inside shell. This power dissipation result slightly elevated temperature reading. RS-485 Line Termination Using termination resistor 485DTT driver drastically increases power consumption, increasing internal heating. this reason using terminating resistor RS-485 lines connected 485DTT driver recommended. found that termination necessary, terminating technique eliminate power consumption simple resistive termination. brief discussion termination found Electronics' free RS-422/RS-485 Application Note. Multidrop Applications programmable address feature 485DTT allows different devices multidropped same RS-485 network. RS-485 allows devices same network, extend that number, RS-485 repeaters used. Figure shows typical RS-485 two-wire multidrop network using 485DTT.
Documentation Number 485DTT1795 Manual Chapter Electronics 1040 Ottawa, 61350 (815) 433-5100 (815) 433-5105
Figure 485DTT Multidrop Configuration
Chapter Documentation Number 485DTT1795 Manual Electronics 1040 Ottawa, 61350 (815) 433-5100 (815) 433-5105
Chapter Software
There both program (DTT_DOS.EXE) Windows program (485DTT_W.EXE) which allows read current temperature either Fahrenheit Celsius, address, turn around delay, well upper lower thresholds. Installation install your hard drive follow these steps: Place disk drive Type press ENTER key. Type INSTALL press ENTER key.
Windows Setup After software installed onto your hard disk, following files should located 485DTT directory: 485DTT_W.EXE, VBRUN300.DLL, MSCOMM.VBX. 485DTT under Windows follow these steps: Windows. Select "FILE" menu under Program Manager. Select "NEW" option. From "New Program Object" window select "Program Item" option then select "OK". From "Program Item Properties" window: Type "Description" box: 485DTT Type "Command Line" box: C:\485DTT\485DTT_W.EXE From "Program Item Properties" menu select "OK" option. Setup 485DTT software complete. 485DTT icon should appear current window. Simply double click icon execute program.
Documentation Number 485DTT1795 Manual Chapter Electronics 1040 Ottawa, 61350 (815) 433-5100 (815) 433-5105
Appendix Using SimpTerm
Electronics shareware terminal program, SimpTerm, included floppy disk. SimpTerm powerful troubleshooting tool which will allow communicate through four serial ports address interrupt. will need know address interrupt serial port that connected SimpTerm communicate with DTT, follow instructions open port connected DTT. Check that unit powered with external power supply. Check that baud rate anywhere from 1200 9600 baud. Type following command: !0RT. second character address character (factory programmed zero). commands must capital letters. will respond with characters indicating temperature. Room temperature usually followed character close ASCII table comma. indicated <0>. register follow, type following: !0SH<0>2. decimal value ASCII This corresponds indicates that positive value.* read back value stored register, type following command: !0RH. step been successfully completed will respond with <0>2. actually character represented keyboard key. SimpTerm allows these characters transmitted using following procedure: Hold down key, type decimal value (two digits) numeric keypad release key. example, transmitted [release ALT].
Documentation Number 485DTT1795 Manual Appendix Electronics 1040 Ottawa, 61350 (815) 433-5100 (815) 433-5105
Appendix Decimal/ASCII Table
DECIMAL ASCII CONVERSION TABLE
ASCII ASCII ASCII ASCII
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Documentation Number 485DTT1795 Manual Appendix Electronics 1040 Ottawa, 61350 (815) 433-5100 (815) 433-5105

Digital Thermometer Thermostat with RS-485 Interface Model 485DTT

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