The CM board is one of the important devices in the 75F BMS. On this device, the 75F CCU tablet is mounted.
CCU is the device that aggregates all the data from a building and other smart devices which are connected to the CCU, and the CM board is the device that is responsible for the data transmission to the cloud via the 900Mhz mesh network.
The data that is sent to the cloud is what is being visualized as the information in the Facilisight and the mobile apps.
The CM board comprises a combination of switches, relays, jumpers, and other components which are responsible for different operations.
Below is the information about a few of the important components of the CM board that is good to know as an installer o the 75F system, and helps in installation.
| CM Board
At this position, it is a reset switch, when pressed the button the CM board resets the 5V power cycle.
At this position, it is another reset switch, when it is pressed the microprocessor in the CM board is reset.
At this position, two jumpers or short links are used, one on the left-hand side is to enable the +5.2V power to the RS485 circuit when used, and the one on the right-hand side is to add a terminal resistor for the RS485 circuit.
If the short links or jumpers are not used, +5.2V power is disconnected from the RS485 circuit and the terminal resistor is not added to the RS485 circuit.
At this position, 4 jumpers are used to switch between the voltage and current types of output; 2-10V or 4-20mA.
The pin for the voltage denoted by 'V' is shorted with the pin in the center to switch for voltage output.
The pin for the current denoted by 'I' is shorted with the pin in the center to switch for current output.
Below is an illustration of the possible jumper location for all the analog outputs:
At this position, a connector is used to enable the connection of the RS485 cable. The connector is generally used while connecting a Modbus device to the 75F system in a Modbus communication network.
At this position a connector is used to connect the RTS cable of an RTS sensor, to receive the temperature and humidity data.
At this position is a debug port to connect the FTDI cable for collecting serial logs which are used for debugging.
At this position, a jumper is used so that the relay terminals are internally powered up from the 24V power supply provided by the CM board.
At this position, a jumper is used so that the rest of the board is powered-up from the connected isolation power of +5.2V.
At this position we have the relay terminals, following are the details of the same from left to right
- Terminals 1 and 2, are GND and External Power input terminal
- Terminals 3 and 4 are Y1 and Y2 terminals Cooling stages 1 and 2
- Terminal 5 is the G1 terminal for Fan stage 1
- Terminals 6 and 7 are W1 and W2 terminals Heating stages
- Th terminal 8 is the G2 terminal for Fan Stage2.
At this position, there is a terminal for Auxiliary Relay.
At this position, 3 jumpers are used for the following purposes.
- A jumper is used for the R and Rc pins of the berg strip to connect the external power to relay the common bus.
- A jumper was used for the R and Rh pins of the berg strip to connect the 24V AC power to power up the relay terminals for heaters.
- A jumper was used for the R and Ra1 pins of the berg strip to connect the 24 AC power to power up the relay terminals for auxiliary units.
At this position we have the Analog Output Terminal, following are the details of the same from left to right
- The terminals 1 and 2 are GND and AO1, to measure voltage or current.
- The terminals 3 and 4 are GND and AO2, to Measure voltage or current.
- The terminals 5 and 6 are GND and AO3, to Measure voltage or current.
- The terminals 7 and 8 are GND and AO4, to Measure voltage or current.
At this position, there are the Input terminals, following are the details of the same from left to right
- terminal 1 is GND used for Analog Inputs.
- The terminal 2 is positive TH1 used for Thermistor Inputs.
- The terminal 3 is positive TH2 used for Thermistor Inputs.
- The terminal 4 is positive AI1 used for Analog Inputs.
- The terminal 5 is positive AI2 used for Analog Inputs.
- terminal 6 is for GND.
- terminal 7 is for 5V DC supply.
At this position, there is a Daughter Card, which is a replacement for the pins J28 jumper used in the 10-inch CM board, and it is a 5x 2 programming pin.
And those are the CM board configurations and settings.
Relay-connect, cooling, Rh, Ra1 Terminals, Jumper Operation, and Significance.
The R-connect, Rc, Rh, and Ra1 terminals are very important terminals of the CM board, and their part and operation when used with or without jumpers can affect the controls in the BMS to a great extent.
Below is an illustration of the parts and operations of these terminals.
When a jumper is not used in the R-connect terminal to short the points, the 24V power ends at the R-connect terminal and the same does not progress anywhere.
When a jumper is used in the R-connect terminal to short the points, the 24V power progresses and is made available at the Rc, Rand h, and Ra1 for the various relays to use the same.
When jumpers are used in the Rc, Rh, and Ra1 terminals, the 24V power supply which is made available at the Rc, Rh, and Ra1 for the various relays to use, is further made available as the primary circuit power supply for the actual relays.
The color blue indicates the supply for the cooling and cooling stage-related relays Rc, Y1, Y2 & G1.
The color red indicates the supply for the heating and heating stage-related relays Rh, W1, W2 & G2.
The color green indicates the supply for the auxiliary relays RL-SPR & RL_AUX1.
Based on the actual building requirement, the jumper can be used or not used, to achieve the required controls and operations.
| Antenna Types
The CM board is provisioned with an internal antenna option, to cater to the receiving and transmitting capabilities. For situations demanding an enhanced capability of receiving and transmitting the CM board. An external antenna can be made available in the CM board.
In the above image for the CM, the highlighted section of the CM is where the configuration of different types of Antennas is enabled.
Internal Antenna Configuration
A CM board manufactured with the Internal Antenna configuration comes with a horizontal resistor as shown above. And the connector provided is just idle for this configuration.
External Antenna Configuration
A CM board manufactured with the External Antenna configuration comes with a vertical resistor as shown above. And the connector provided here can be utilized to wire the antenna for an extended length away from the CM, to avoid noises and distractions.