The OB-216 is a digital input/output module manufactured by NOVATEK-ELECTRO LTD. It provides versatile measurement and control capabilities via RS-485 and USB interfaces using the ModBus protocol, with analog output functionality.
Digital input/output module OB-216 (hereinafter referred to as the Device or OB-216) can be used as:
remote DC voltage meter (0 – 10 V);
remote meter of direct current (0 – 20 mA);
remote temperature meter when connecting an analog sensor NTC (10KB), PTC 1000 or PT 1000;
remote temperature or humidity meter when connecting a digital sensor DS18B20, DHT21, DHT22 or AM2301;
counter of impulses with saving the result in memory.
OB-216 provides:
monitoring the state (closed / open) of the contact at the input of the «dry contact» type;
issue of an analog signal (0 - 10 V, 0 - 20 mA) at the analog output.
RS-485 or USB interfaces provide control over the ModBus protocol of devices connected to the analog output (Figure 1, pos. 9, 10), reading sensor readings, setting device parameters. The control is carried out using the program “Control Panel OB-215/OB-216” or other software supporting the MODBUS protocol.
Power supply of the device and data exchange are indicated by indicators on the front panel (Fig. 1, pos. 2, 3).
The overall and mounting dimensions and controls of OB-216 are shown in Figure 1.
1 – microUSB connector;
2 – data exchange indicator;
3 – power supply indicator;
4 – terminals for RS-485 connection;
5 – terminals for power supply;
6 – terminal for restarting the device;
7 – terminals for connecting sensors;
8 – terminal “ground” of the analog output;
9 – current terminal 0 - 20 mA analog output;
10 – voltage terminal 0 - 10 V analog output.
Figure 1 – OB-216 front panel and overall dimensions
Temperature and threshold settings (Addresses 102–105)
Parameter
Value range
Factory value
Type
W/R
Address (DEC)
Temperature correction
–99…99
0
INT
W/R
102
Working parameter*
0…1
0
UINT
W/R
103
Upper threshold
-32767…32767
250
INT
W/R
104
Lower threshold
–32767…32767
0
INT
W/R
105
Working parameter values:
0 – temperature
1 – humidity
Settings for the pulse counter (Addresses 106–108)
Parameter
Value range
Factory value
Type
W/R
Address (DEC)
Pulse counter mode
0…2
0
UINT
W/R
106
Contact debouncing delay**
1…250
10
UINT
W/R
107
Number of pulses per counting device***
1…65534
8000
UINT
W/R
108
Pulse counter mode values:
0 – counter on the leading edge of the pulse
1 – counter on the trailing edge of the pulse
2 – counter on both pulse edges
Data transfer settings (Addresses 109–116)
Parameter
Value range
Factory value
Type
W/R
Address (DEC)
RS-485 protocol
0…1
0
UINT
W/R
109
MODBUS UID
1…247
28
UINT
W/R
110
Exchange rate
0…8
3
UINT
W/R
111
Parity and stop bits control
0…2
0
UINT
W/R
112
Interface selection
0…2
0
UINT
W/R
113
Password protection ModBus****
0…1
0
UINT
W/R
116
ModBus password value
A–Z, a–z, 0–9
admin
STRING
W/R
117–124
RS-485 protocol values:
0 – MODBUS RTU
1 – MODBUS ASCII
Exchange rate values:
0 – 1200
1 – 2400
2 – 4800
3 – 9600
4 – 14400
5 – 19200
6 – 38400
7 – 57600
8 – 115200
Parity and stop bits control values:
0 – no, 2 stop bits
1 – even, 1 stop bit
2 – odd, 1 stop bit
Interface selection values:
0 – automatically
1 – RS-485
2 – USB
Measured value conversion settings (Addresses 130–134)
Parameter
Value range
Factory value
Type
W/R
Address (DEC)
Measured value conversion
0…1
0
UINT
W/R
130
Minimum input value
0…2000
0
UINT
W/R
131
Maximum input value
0…2000
1000
UINT
W/R
132
Minimum converted value
–32767…32767
0
INT
W/R
133
Maximum converted value
–32767…32767
1000
INT
W/R
134
Measured value conversion values:
0 – conversion is disabled
1 – conversion is enabled
Settings for analog output (Addresses 150–156)
Parameter
Value range
Factory value
Type
W/R
Address (DEC)
Analog output control
0…4
0
UINT
W/R
150
Register for writing value in manual mode
0…2000
0
UINT
W/R
151
Converting the manual control value to analog signal
0…1
0
UINT
W/R
152
Minimum input value
–500…2500
0
INT
W/R
153
Maximum input value
–500…2500
1000
INT
W/R
154
Minimum converted analog value
0…2000
0
UINT
W/R
155
Maximum converted analog value
0…2000
1000
UINT
W/R
156
Analog output control values:
0 – control is disabled
1 – automatic control of voltage output
2 – automatic control of current output
3 – manual control of voltage output
4 – manual control of current output
Converting the manual control value to analog signal values:
0 – conversion is disabled
1 – conversion is enabled
Notes:
* Used parameter of the selected digital sensor (address 101).
** Delay in milliseconds used to suppress contact bounce in the «Pulse counter» and «Logic input/pulse relay» modes.
*** Used only if pulse counter is enabled. The «Value» column indicates the number of pulses at the input, after the registration of which the counter is increased by one. Writing to memory is performed at intervals of 1 minute.
**** If «ModBus password protection» is enabled (address 116 value «1»), then to access the recording functions, must be write the correct password value to addresses 51-58.
Temperature Measurement Error When Using Analog Sensors
The device is intended for operation in the following conditions:
Ambient temperature: from minus 35 to +45 °С
Atmospheric pressure: from 84 to 106.7 kPa
Relative humidity (at temperature of +25 °С): 30 … 80 %
If the temperature of the device after transportation or storage differs from the ambient temperature at which it is supposed to be operated, then before connecting to the mains keep the device under the operating conditions within two hours (because of condensation may be on the product elements).
An error during installation work can damage the unit and appliances connected to it.
For reliable contact, it is necessary to tighten the terminal block screws with force of 0.4 N·m.
When the tightening torque is reduced, the junction may heat up, the terminal block may melt and the wire may catch fire. With an increase in the tightening torque, it is possible that the threads of the terminal block screws are broken or the wire to be connected is pinched.
Figure 3 – Wiring diagram for operation with digital sensors
1. Connect the device in accordance with Figure 2 (when using the device in the mode of measuring analog and discrete signals) or in accordance with Figure 3 (when using the device with digital sensors) and check the correct connection. To connect the device to the ModBus network, use a twisted pair cable of Cat.1 category or higher.
2. Check the correct connection according to «Connecting different types of sensors» and the diagrams in Figure 2 or Figure 3.
After power is applied, the indicator « ⏻ » flashes for 1.5 s, then the indicators « ⏻ » and «RS-485» (Fig. 1, pos. 2, 3). After 0.5 s, the «RS-485» indicator goes out. During data exchange, the «RS-485» flashes, otherwise the indicator does not light up.
To configure the device, use the program «Control Panel OB-215/OB-216» (available at website www.novatek-electro.com in the «Software» section) or other software compatible with the ModBus RTU/ASCII. The program connects to the device via USB or RS-485 interface.
Connect an external device according to Figure 2 (e). Configure the device for operation in the pulse counter mode for counting discrete signals («OB-216 setting», address 100, value 0). In the register (address 106) to select the pulse detection algorithm.
In this mode, the device counts the number of pulses at the «IO2» (input with a duration not less than the value specified in the «OB-216 settings», address 107, the value is specified in ms) and saves the data into memory with a frequency of 1 minute. If the device was switched off before 1 minute has elapsed, the last stored value will be restored when switched on.
Upon reaching the value indicated in the register (address 108), the counter is incremented by one («Additional registers», address 4:5).
To configure the initial value of the pulse counter, write the required value into the register («Additional registers», address 4:5). Then the counter will count pulses from the entered value.
When changing the value in the register (address 108), all stored pulse counter values will be deleted.
Connect an external device according to Figure 2 (f). Configure OB-216 to operate in the pulse counter mode for counting voltage pulses («OB-216 settings», address 100, value 11). In register (address 106) select the pulse detection algorithm. In registers (addresses 104, 105) specify the upper and lower voltage thresholds at which the pulse will be counted.
In this mode, the device counts the number of voltage pulses in accordance with the set thresholds. If the voltage value changes within the upper and lower thresholds, the device will not register these pulses. The number of impulses is saved to memory every minute. If the device was switched off before 1 minute has elapsed, the last stored value will be restored when switched on.
Upon reaching the value indicated in the register (address 108), the counter is incremented by one («Additional registers», address 4:5).
To configure the initial value of the pulse counter, write the required value into the register («Additional registers», address 4:5). Then the counter will add pulses to the initial value.
When changing the value in the register (address 108), all stored pulse counter values will be deleted.
Connect an external device according to Figure 2 (f). Configure OB-216 to operate in the impulse counter mode for counting current impulses («Device settings», address 100, value 12). In register (address 106) select the impulse detection algorithm. In registers (addresses 104, 105) specify the upper and lower current thresholds at which the impulse will be recorded.
In this mode, the device counts the number of current impulses in accordance with the set thresholds. If the current value changes within the upper and lower thresholds, the device will not register these impulses. The number of impulses is saved to memory every minute. If the device was switched off before 1 minute has elapsed, the last stored value will be restored when switched on.
Upon reaching the value indicated in the register (address 108), the counter is incremented by one («Additional registers», address 4:5).
To configure the initial value of the impulse counter, write the required value into the register («Additional registers», address 4:5). Then the counter will add pulses to the initial value.
When changing the value in the register (address 108), all stored impulse counter values will be deleted.
Connect the device according to Figure 2 (d). Configure it for operation in the «Logic input» («OB-216 settings», address 100, value 1).
When the logical state at the «IO2» terminal (Fig. 1, item 7) changes to a low level, the device will set bit 18 («Additional registers», address 2:3) equal to 1.
When the logical state at the «IO2» terminal (Fig. 1, pos. 7) changes to a high level, the device will set bit 18 («Additional registers», address 2:3) equal to 0.
Connect the device according to Figure 2(b). Configure it to operate in the «Voltage measurement» («OB-216 settings», address 100, value 2). The register («Additional registers», address 6) will display the voltage measured at the «IO1» (Fig. 1, pos. 7).
If it is necessary for the device to indicate overvoltage (under voltage), it is necessary to set the response thresholds («OB-216 settings», addresses 104, 105). To set the thresholds, write down the values in address 104 – upper threshold and address 105 – lower threshold. When the voltage value is exceeded (decreased), the corresponding bit will be set to «1» (bit 20 – voltage value above the upper threshold, bit 21 – voltage value below the lower threshold) («Additional registers», address 2:3).
To convert the measured voltage to another value, turn on the conversion («OB-216 setting», address 130, value 1) and set the conversion ranges (addresses 131 – 134).
For example, the measured voltage needs to be converted to bars with the following sensor parameters: a voltage range of 0.5 V to 8 V corresponds to a pressure of 1 bar to 25 bar. Configuring the conversion ranges: minimum input value (address 131, value 50 corresponds to 0.5 V), maximum input value (address 132, value 800 corresponds to 8 V), minimum converted value (address 133, value 1 corresponds to 1 bar), maximum converted value (address 134, value 25 corresponds to 25 bar).
The converted value will be output to a register («Additional registers», address 16).
To output the measured voltage to the analog current output, select the analog current output by writing to the register (address 150) the value 2 – current output control (Fig. 1, pos. 9).
For example, to convert a measured voltage in the 1 V to 10 V range to a current (4 mA to 20 mA range), the conversion ranges must be set.
To set the ranges, write down the minimum value of the input voltage (100 = 1 V) into the register (address 153), and into the register (address 154) write down the maximum value of the input voltage (1000 = 10 V). In the register (address 155) write the minimum value of the output current (400 = 4 mA), in the register (address 156) – the maximum value of the output current (2000 = 20 mA).
The converted analog value will be output to a register («Additional registers», address 17).
To output the measured voltage to the analog voltage output, select the analog voltage output by writing to the register (address 150) the value 1 – voltage output control (Fig. 1, pos. 10).
For example, to convert a measured voltage in the 1 V to 10 V range to a voltage (0 V to 5 V range), the conversion ranges must be set.
To set the ranges, write down the minimum value of the input voltage (100 = 1 V) into the register (address 153), and into the register (address 154) write down the maximum value of the input voltage (1000 = 10 V). In the register (address 155) write the minimum value of the output voltage (0 = 0 V), in the register (address 156) – the maximum value of the output voltage (500 = 5 V).
The converted analog value will be output to a register («Additional registers», address 17).
To output voltage to the analog output in manual mode, select the analog voltage output by writing the value 3 to the register (address 150) - manual control of the voltage output (Fig. 1, pos. 10). To convert a manually set value, turn on the conversion of the output value by writing the value «1» to the register (address 152) and the required ranges in the corresponding registers (addresses 153-156).
When the value «500», is written to the register (address 151), a voltage with a level equal to 5.00 V will appear at the output of the analog voltage (Fig.1, pos. 10) (when the conversion of the output value is disabled).
Connect the device according to Figure 2 (a). Configure it for operation in the «Current measurement» mode («OB-216 settings», address 100, value 3). The register («Additional registers», address 6) will display the value of the current measured at the «IO1» terminal (Fig. 1, pos. 7).
If it is necessary for the device to indicate an excess (decrease) in current, it is necessary to set the response thresholds («OB-216 settings», addresses 104, 105).
To set the thresholds, write down the values in address 104 - high threshold and address 105 - low threshold. When the current value is exceeded (decreased), the corresponding bit will be set to «1» (bit 22 - the current value is above the upper threshold, bit 23 - the current value is below the lower threshold) («Additional registers», address 2:3).
To convert the measured current into another value, turn on the conversion («OB-216 settings», address 130, value 1) and set the conversion ranges (addresses 131 - 134).
For example, the measured current needs to be converted to bars with the following sensor parameters: a current range of 4.5 mA to 20 mA corresponds to a pressure of 1 bar to 25 bar. Configuring the conversion ranges: minimum input value (address 131, value 450 corresponds to 4.5 mA), maximum input value (address 132, value 2000 corresponds to 20 mA), minimum converted value (address 133, value 1 corresponds to 1 bar), maximum converted value (address 134, value 25 corresponds to 25 bar).
The converted value will be output to a register («Additional registers», address 16).
Current Measurement with Output to Analog Current Output
To output the measured current to the analog current output, select the analog current output by writing to the register (address 150) the value 2 - current output control (Fig. 1, item 9).
For example, to convert the measured current, in the range from 0 mA to 10 mA, to current (range from 4 mA to 20 mA), adjust the conversion ranges.
To set the ranges, write the minimum value of the input current (0=0 mA) into the register (address 153), and into the register (address 154) – the maximum value of the input current (1000 = 10mA). In the register (address 155) write the minimum value of the output current (400 = 4 mA), in the register (address 156) – the maximum value of the output current (2000 = 20 mA).
To output the measured current to the analog output, select the analog voltage output by writing the value 1 to the register (address 150) – voltage output control (Fig. 1, pos. 10).
For example, to convert the measured current, in the range from 0 mA to 20 mA, to voltage (range from 0 V to 5 V), the conversion ranges must be set. To set the ranges, write the minimum value of the input current (0 = 0 mA) to the register (address 153), and the maximum value of the input current (2000 = 20 mA) to the register (address 154). In the register (address 155) write the minimum value of the output voltage (0 = 0 V), in the register (address 156) – the maximum value of the output voltage (500 = 5 V).
To output the current to the analog output in manual mode, select the analog current output by writing the value 4 to the register (address 150) – manual control of the current output (Fig. 1, item 9).
To convert a manually set value, turn on the conversion of the output value by writing the value «1» to the register (address 152) and the required ranges in the corresponding registers (addresses 153 - 156).
When the value «500» is written to the register (address 151), a current with a level equal to 5.00 mA will appear at the analog current output (Fig. 1, pos. 9) (when the conversion of the output value is disabled).
Connect the device according to Figure 2 (c). Configure it for operation in the «Temperature measurement» («OB-216 settings», address 100, value 4, 5, 6). If it is necessary for the device to react to an excess (decrease) of temperature, set the response thresholds («OB-216 settings», addresses 104, 105). To set the thresholds, write down the values to address 104 – upper threshold and address 105 – lower threshold. When the temperature value is exceeded (decreased), the corresponding bit will be set to «1» («Additional registers», address 2:3, bits 24, 25).
If it is required to correct the temperature measured by the sensor, enter the correction temperature into register 102 (OB-216 settings). Value input format: 55 = 5.5 °С.
In this mode, the device measures the temperature using a thermistor. The measured temperature value can be read at address 6 (Additional registers).
Temperature values are displayed with an accuracy of tenths of a degree Celsius (1234 = 123.4 °С; 123 = 12.3 °С).
To output the measured temperature to the analog output, select the analog voltage output by writing in the register (address 150) the value «1» (control of the voltage output, Fig. 1, item 10) or value «2» (control of the current output, Fig. 1, item 9) and set up the conversion range registers (addresses 153 – 156).
The device supports digital (single) sensors specified in the «OB-216 settings» (address 101).
The measured values of the digital sensor can be read at addresses 11 – 12, «Additional registers» (depending on which values the sensor measures). Interrogation period of digital sensors – 3 s.
If it is required to correct the temperature measured by a digital sensor, it is necessary to enter the correction temperature into register 102 (OB-216 Settings).
If it is necessary for the device to react to the excess (decrease) of the operating parameter, it is necessary to select the operating parameter («OB-216 settings», address 103), and set the response thresholds (addresses 104, 105). When the value of the operating parameter is exceeded (decreased), the corresponding bit will be set to «1» (excess (decrease) of temperature – bit 24, bit 25 («Additional registers», address 2:3), excess (decrease) of humidity – bit 26, bit 27 (address 2:3)).
Temperature values are displayed with an accuracy of tenths of a degree Celsius (1234 = 123.4 °С; 123 = 12.3 °С).
Moisture values are displayed with an accuracy of tenths of a percent (800 = 80.0 %).
Connection of Digital Sensors with Output to Analog Output
To output the operating parameter of the digital sensor («OB-216 settings», address 103) to the analog output, select the analog voltage output by writing the value «1» to the register (address 150) (voltage output control, Fig. 1, pos. 10) or value «2» (current output control, Fig. 1, pos. 9) and set the registers of the conversion ranges (addresses 153 – 156).
9 Restarting the Device and Resetting to the Factory Settings
If you need to restart the device, close and hold contacts «R» and «–» for 3 seconds (Fig. 1).
If it is required to restore the factory settings of the device, it is necessary to close and hold contacts «R» and «–» (Fig. 1) for more than 10 seconds. After 10 seconds, the device will automatically restore factory settings and reboot.
Also, the above actions can be performed through the command register by writing the corresponding command into it («Command register», address 50).
10 Work with RS (EIA/TIA)-485 and USB Interface via ModBus Protocol
If the register (address 113) contains the value «0» (automatic selection of the interface), the device will automatically switch to work with USB, if OB-216 is connected to the PC via a USB cable. Otherwise, the device works with the RS-485 interface.
To work only with the RS-485 interface, it is necessary to write the value «1», to the register (address 113); with this setting, the device will not switch to work with USB when the cable is connected.
To work only with the USB interface, it is necessary to write the value «2», to the register (address 113), with this setting the device will work only with the USB interface, and access to the device via RS-485 will be prohibited.
OB-216 allows data exchange with external devices via the RS (EIA/TIA)-485 serial interface via the ModBus protocol with a limited set of commands (the list of supported functions is given in the table below).
When building a network, the master-slave organization principle is used, where OB-216 acts as a slave. Only one master and several slaves can be present on the network. A personal computer or a programmable logic controller acts as a master node.
With this organization, only the master node can act as the initiator of exchange cycles.
Host requests are individual (addressed to a specific device).
OB-216 transmits in response to individual requests from the master.
If errors are detected in receiving requests, or if it is impossible to execute the received command, OB-216, as a response, generates an error message.
The addresses (in decimal) of the command registers and their purpose are shown in the «List of Supported Functions».
Addresses (in decimal) of additional registers and their purpose are given in the «Command Register.
61989 – reset the impulse counter (this will clear all values stored in the flash memory)
Name
Description
W/R
Address (DEC)
Entering ModBus password (8 ASCII characters)
Set the correct password to access the recording functions (default value is “admin”). To disable recording functions, set any value other than a password. Allowed characters: A-Z; a-z; 0-9
W/R
51 – 58
Notes:
W/R – type of access to the register write/read;
an address like “50” means a 16-bit value (UINT);
address like “51 – 58” mean a range of 8-bit values.
OB-216 is configured to operate with one of two formats of data bytes: with parity control (Fig. 4) and without parity control (Fig. 5). In parity control mode, the type of control is also indicated: Even or Odd. Transmission of data bits is performed by the least significant bits forward.
By default (during manufacture) the device is configured to operate without parity control and with two stop bits.
Byte transfer is performed at speeds of 1200, 2400, 4800, 9600, 14400 and 19200 bps. By default, during manufacturing, the device is configured to operate at a speed of 9600 bps.
Figure 4, 5 – Byte format with parity control (top) and without parity control (bottom)
The frame length cannot exceed 256 bytes for ModBus RTU and 513 bytes for ModBus ASCII.
In ModBus RTU mode the start and end of the frame are monitored by silence intervals of at least 3.5 bytes. The frame must be transmitted as a continuous byte stream. The correctness of frame acceptance is additionally controlled by checking the CRC checksum.
The address field occupies one byte. The addresses of the slaves are in the range from 1 to 247. Fig. 6 shows the RTU frame format.
Figure 6 – RTU frame format
In ModBus ASCII mode the start and end of the frame are controlled by special characters (symbols (’:’ 0x3A) – for start of the frame; symbols (‘CRLF’ 0x0D0x0A) – for the end of the frame). The frame must be transmitted as a continuous stream of bytes. The correctness of frame acceptance is additionally controlled by checking the LRC checksum.
The address field occupies two bytes. The addresses of the slaves are in the range from 1 to 247. Fig. 7 shows the ASCII frame format.
The transmitting device generates a checksum for all bytes of the transmitted message. OB-216 similarly generates a checksum for all bytes of the received message and compares it with the checksum received from the transmitting device. If the generated and received checksums do not match, an error message is generated.
The checksum in the message is sent by the least significant byte forward, it is a cyclic verification code based on the irreducible polynomial 0xA001.
Subroutine for CRC checksum generation in C language:
Function 0x03 provides reading of the contents of registers OB-216. The master query contains the address of the initial register, as well as the number of words to read.
The OB-216 response contains the number of bytes to return and the requested data. The number of registers returned is limited to 50. If the number of registers in the query exceeds 50 (100 bytes), the response is not divided into frames.
An example of the query and response in ModBus RTU is shown in Fig. 8.
Figure 8 – Example of reading registers (Function 0x03)
The function 0x06 provides recording in one OB-216 register. The master query contains the address of the register and the data to be written.
The device response is the same as the master query and contains the register address and the set data. An example of the query and response in ModBus RTU mode is shown in Fig. 9.
Figure 9 – Example of writing to a register (Function 0x06)
The device in the original package is permitted to be transported and stored at the temperature from minus 45 to +60 °C and relative humidity of no more than 80 %, not in aggressive environment.
Warranty period of the device operation is 5 years from the date of sale.
During the warranty period of operation, the manufacturer performs free repair of the device, if the user has complied with the requirements of the Operating Manual.
Warranty service is performed at the place of purchase or by the manufacturer of the device. Post-warranty service of the device is performed by the manufacturer at current rates.
Before sending for repair, the device should be packed in the original or other packing excluding mechanical damage.
For all questions, please contact the manufacturer:
