The OB-215 is a digital I/O module manufactured by NOVATEK-ELECTRO LTD. It provides versatile measurement and control capabilities via RS-485 interface using the ModBus protocol.
Digital I/O module OB-215 (hereinafter referred to as the device or OB-215) can be used as the following:
remote DC voltage meter (0 – 10 V);
remote DC meter (0 – 20 mA);
remote temperature meter with the ability to connect sensors NTC (10 KB), PTC 1000, PT 1000 or digital temperature sensor DS/DHT/BMP;
temperature regulator for cooling and heating plants;
pulse counter with saving the result in memory;
pulse relay with switching current up to 8 A;
interface converter for RS-485 – UART (TTL).
OB-215 provides:
equipment control using relay output with switching capacity up to 1.84 kVA;
tracking the state (closed/open) of the contact at the dry contact input.
RS-485 interface provides control of the connected devices and reading of the sensors readings via the ModBus protocol.
Parameter setting is set by the user from the Control Panel using the ModBus RTU/ASCII protocol or any other program that allows working with the ModBus RTU/ASCII protocol.
The status of the relay output, the presence of the power supply and the data exchange are displayed using indicators located on the front panel (Fig. 1, it. 1, 2, 3).
The overall dimensions and layout of the device are shown in Fig. 1.
1 – indicator of data exchange via RS-485 interface (it is on when data is being exchanged);
2 – indicator of the status of the relay output (it is on with closed relay contacts);
3 – indicator « ⏻ » is on when there is supply voltage;
4 – terminals for connecting RS-485 communication;
5 – device power supply terminals;
6 – terminal for reloading (resetting) the device;
7 – terminals for connecting sensors;
8 – output terminals of relay contacts (8 А).
Figure 1 – OB-215 front panel and overall dimensions
1 – relay contacts are opened at a value above the upper threshold, they are closed at a value below the lower threshold
2 – relay contacts are closed at a value above the upper threshold, they are opened at a value below the lower threshold
3 – relay contacts are opened at a value above the upper threshold or below the lower threshold and are closed at a value below the upper threshold and above the lower threshold
4…7 – similarly 0…3 respectively, for the secondary parameter of the digital sensor
Timeout of communication before relay disconnection, s (Used when relay control is disconnected)
0…36000
0
UINT
W/R
128
Relay pulse period, ms (Used when relay control is disabled)
20…20000
200
UINT
W/R
129
Value conversion settings
Description
Range
Factory setting
Type
W/R
Address (DEC)
Value Conversion: 0 – disabled; 1 – enabled
0…1
0
UINT
W/R
130
Minimum Input Value
0…2000
0
UINT
W/R
131
Maximum Input Value
0…2000
2000
UINT
W/R
132
Minimum Converted Value
-32767…32767
0
INT
W/R
133
Maximum Converted Value
-32767…32767
2000
INT
W/R
134
Notes:
W/R – type of access to the register as write/read.
* The sensor to be connected is selected at address 101.
** The delay used in switch debouncing in the Logic Input/Pulse Relay mode; the dimension is in milliseconds.
*** Only used if the pulses counter is on. The column “Value” indicates the number of pulses at the input, after registration of which, the counter is incremented by one. Recording to memory is performed with a periodicity of 1 minute.
**** If ModBus Password Protection is enabled (address 116, value “1”), then to access the recording functions, you must write the correct password value to addresses 51-59.
The product 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 product 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 product under the operating conditions within two hours (because of condensation may be on the product elements).
It is not allowed to leave exposed portions of wire protruding beyond the terminal block.
Error when performing the installation works may damage the device and connected devices.
For a reliable contact, tighten the terminal screws with the force indicated in Table 1.
When reducing the tightening torque, the junction point is heated, the terminal block may be melted and wire can burn. If you increase the tightening torque, it is possible to have thread failure of the terminal block screws or the compression of the connected wire.
Connect the device as shown in Fig. 2 (when using the device in the analog signals measurement mode) or in accordance with Fig. 3 (when using the device with digital sensors). A 12 V battery can be used as a power source. Supply voltage can be read (Table 6, address 7).
To connect the device to the ModBus network, use CAT.1 or higher twisted pair cable.
After the power is on, the indicator « ⏻ » lights up. The indicator flashes for 1.5 seconds. Then the indicators and «RS-485» light up (Fig. 1, pos. 1, 2, 3) and after 0.5 second they go out.
To change any parameters you need:
download the OB-215/OB-216 Control Panel program at www.novatek-electro.com or any other program that allows you to work with ModBus RTU/ASCII protocol.
connect to the device via RS-485 interface;
perform the necessary settings for the OB-215 parameters.
During the data exchange, the “RS-485” indicator flashes, otherwise the “RS-485” indicator does not light up.
In this mode, the device measures the readings of sensors connected to the inputs “IO1” or “IO2” (Fig. 1, it. 7), and depending on the settings, performs the necessary actions.
In this mode, the device converts the data received via the RS-485 interface (Modbus RTU/ASCII) to the UART (TTL) interface (Table 2, address 100, value “7”). More detailed description see in Transformation of UART (TTL) interfaces to RS-485.
Connect the external device as shown in Fig. 2 (e). Set up the device for operation in the Pulse Counter Mode (Table 2, address 100, value “0”).
In this mode, the device counts the number of pulses at the input “IO2” (of duration no less than the value indicated in Table 2, Address 107, value in ms) and stores the data in memory with a periodicity of 1 minute. If the device has been turned off before 1 minute has ended, the last stored value will be restored upon power-up.
If you change the value in the register (Address 108), all the stored values of the pulse meter will be deleted.
When the value specified in the register (address 108) is reached, the counter is incremented by one (Table 6, address 4:5).
To set the initial value of the pulse counter it is necessary to write-down the required value into the register (Table 6, address 4:5).
When selecting Logic Input/Pulse Relay mode (Table 2, Address 100, Value 1), or changing the Pulse meter mode (Table 2, Address 106), if the relay contacts were closed “C – NO” (LED lights up), the device will automatically open the “C-NO” contacts (LED turns off).
Logic Input Mode
Connect the device according to Fig. 2 (d). Set up the device for operation in the Logic Input/Pulse Relay Mode (Table 2, address 100, value “1”), set the required pulse count mode (Table 2, address 106, value “2”).
If the logic state on the “IO2” terminal (Fig. 1, it. 6) changes to a high level (rising edge), the device opens the contacts of the “C - NO” relay and closes the contacts of the “C - NC” relay (Fig. 1, it. 7).
If the logic state on the “IO2” terminal (Fig. 1, it. 6) changes to a low level (falling edge), the device will open the contacts of the “C - NC” relay and close the “C - NO” contacts (Fig. 1, it. 7).
Pulse Relay Mode
Connect the device according to Fig. 2 (d). Set up the device for operation in the Logic Input/Pulse Relay Mode (Table 2, address 100, value “1”), set Pulse Counter Mode (Table 2, address 106, value “0” or value “1”). For short-time pulse with duration of at least the value specified in Table 2 (Address 107, the value in ms) at the «IO2» terminal (Fig. 1, it. 6), the device closes the contacts of the “C - NO” relay and opens the contacts of the “C - NC” relay.
If the pulse is repeated for a short time, the device will open the contacts of the “C - NO” relay and close the “C - NC” relay contacts.
Connect the device according to Fig. 2 (b). Set up the device for operation in the Voltage measurement mode (Table 2, address 100, value “2”). If it is necessary that the device monitors the threshold voltage, it is required to write a value other than “0” in the “Relay control” register (Table 2, address 103). If required, set the operation thresholds (Table 2, address 104 – upper threshold, address 105 – lower threshold).
In this mode, the device measures the DC voltage. The measured voltage value can be read at address 6 (Table 6).
Voltage values are derived to one hundredth of a volt (1234 = 12.34 V; 123 = 1.23 V).
Connect the device according to Fig. 2 (a). Set up the device for operation in the “Current measurement” mode (Table 2, address 100, value “3”). If it is necessary for the device monitors the threshold current, it is required to write a value other than “0” in the “Relay control” register (Table 2, address 103). If required, set the operation thresholds (Table 2, address 104 – upper threshold, address 105 – lower threshold).
In this mode, the device measures DC. The measured current value can be read at address 6 (Table 6).
Current values are derived to one hundredth of a milliampere (1234 = 12.34 mА; 123 = 1.23 mА).
Connect the device according to Fig. 2 (c). Set up the device for operation in the Temperature measurement mode (Table 2, address 100, value “4”, “5”, “6”). If it is necessary for the device monitors the threshold temperature value, it is required to write a value other than “0” in the register “Relay control” (Table 2, address 103). For set the operation thresholds to write a value in address 104 - upper threshold and address 105 - lower threshold (Table 2).
If it is required to correct the temperature, it is necessary to record the correction factor in the “Temperature Correction” register (Table 2, Address 102). In this mode, the device measures the temperature with the help of thermistor.
Temperature values are derived to one tenth of a Celsius degree (1234 = 123.4 °С; 123 = 12.3 °С).
The device supports the digital sensors listed in Table 2 (address 101).
The measured value of the digital sensors can be read at the addresses 11–15, Table 6 (depending on what value the sensor measures). The query time period of digital sensors is 3 s.
In case if it is required to correct the temperature measured by the digital sensor, it is necessary to enter the temperature correction factor in register 102 (Table 2).
If a value other than zero is set in the register 103 (Table 2), the relay will be controlled based on the measured values in register 11 (Table 6).
Temperature values are derived to one tenth of a Celsius degree (1234 = 123.4 °С; 123 = 12.3 °С).
When connecting sensors via the I2C interface, refer to the specific sensor’s passport.
To convert the measured voltage (current) to another value, it is necessary to enable the conversion (Table 2, address 130, value 1) and adjust the conversion ranges.
For example, the measured voltage should be converted to bars with such sensor parameters: voltage range from 0.5 V to 8 V corresponds to a pressure of 1 bar to 25 bar. Conversion Ranges Adjustment: minimum input value (address 131, value of 50 corresponds to 0.5 V), maximum input value (address 132, value of 800 corresponds to 8 V), minimum converted value (address 133, value of 1 corresponds to 1 bar), maximum converted value (address 134, value of 25 corresponds to 25 bars).
Converted value will be displayed in the register (Table 6, address 16).
Restarting the Device and Reset to Factory Settings
If the device needs to be restarted, the “R” and ”–” terminals (Fig. 1) must be closed and held for 3 seconds.
If you want to restore the factory settings of the device, you must close and hold the “R” and ”–” terminals (Fig. 1) for more than 10 seconds. After 10 seconds, the device automatically restores the factory settings and reloads.
Operation with RS (EIA/TIA)-485 Interface via ModBus Protocol
OB-215 allows data exchanging with external devices via the serial interface of RS (EIA/TIA)-485 via ModBus protocol with the limited set of commands (see Table 4 for a list of supported functions).
When constructing a network, the principle of the master-slave organization is used where OB-215 acts as the slave. There can be only one master node and several slave nodes in the network. As the master node is a personal computer or a programmable logic controller. With this organization, the initiator of the exchange cycles can only be the master node.
The queries of the master node are individual (addressed to a particular device). OB-215 performs transmission, responding to individual queries of the master node.
If errors are found in receiving queries, or if the received command cannot be executed, OB-215 as the respond generates an error message.
Addresses (in decimal form) of command registers and their purpose are given in Table 5.
Addresses (in decimal form) of additional registers and their purpose are given in Table 6.
0x37B8 – switch on the relay, then after a preset pulse period (register 129) switch it off
0x472C – write settings to flash memory
0x4757 – load settings from flash memory
0xA4F4 – restart the device
0xA2C8 – reset to factory settings
0xF225 – reset the pulse counter (all the values stored in the flash memory are deleted)
Name
Description
W/R
Address (DEC)
Entering ModBus Password (8 characters ASCII)
To access the recording functions, set the correct password (the default value is “admin”). To disable the recording functions, set any value other than the password. Admissible characters: A-Z; a-z; 0-9
W/R
51 – 59
Notes:
W/R – type of access to the write/read register;
address of the form “50” means the value of 16 bits (UINT);
address of the form “51 – 59” means a range of 8-bit values.
OB-215 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 sending device generates a checksum for all bytes of the transmitted message. OB-215 similarly generates a checksum for all bytes of the received message and compares it with the checksum received from the transmitter. If there is a mismatch between the generated checksum and the received checksum, 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-215. The master query contains the address of the initial register, as well as the number of words to read.
OB-215 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-215 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)
In the interface transformation mode, if the query was not addressed to OB-215, it will be redirected to the device connected to «IO1» and «IO2». In this case the indicator «RS-485» will not change its state.
An example of query and response to the device on UART (TTL) line is shown in Fig. 10.
Figure 10 – Example of query and response to the device on UART (TTL) line
An example of recording to one register of the device on UART (TTL) line is shown in Fig. 11.
Figure 11 – Example of recording to one register of the device on UART (TTL) line
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:
