Controlling ventilation with a carbon dioxide detector MT8057



    Many users of the popular MT8057 carbon dioxide (CO2) detector ask us questions about how to use this detector to control the supply or exhaust ventilation. After reviewing our range, we found a device with which we want to offer a solution to this problem.

    The appearance of the detector can be seen in Fig. 1.


    Fig. 1

    The MP515 module was selected as the power fan control element . The appearance of the module can be seen in Fig. 2


    Fig. 2

    MT8057 is an accurate instrument for measuring CO2 concentration in air. The device is equipped with a liquid crystal display, for precise control and three indicators, for the operational monitoring of carbon dioxide concentration. As a pleasant addition, the device shows the temperature at the place of installation. If necessary, using the control buttons, you can change the inclusion of the operational control indication.

    The MP515 is a power relay with an electronic key. The module is designed to control power appliances up to 2000 watts from low-current outputs of various sensors and control devices, providing galvanic isolation from the appliance. To control the module, a voltage of 1V to 5V is required, which can be obtained from the head unit. The module provides space for the installation of a wireless receiver MK324 433 MHz band. The module can be powered from a + 5V source, for example, PW0512 , or from a USB port of a PC or a charging adapter for a smartphone or phone.

    To connect a power relay, we need to disassemble the MT8057. To do this, use a small screwdriver to bend the latches in the grooves of the sensor housing Fig. 3.


    Fig. 3

    Then unscrew the three screws and disconnect the air intake pipe fig. 4.


    Fig. 4

    Now remove the board and place it on top of the display. Then it will be necessary to solder one of the three wires to the extreme RledR resistor, limiting the current of the red LED with the inscription LedR, Fig. 5.


    Fig. 5 The

    second wire is soldered to the output of the ModeKey button connected to the board's common bus. The third pin is soldered to the middle pin of the THRO element, Fig. 6.


    Fig. 6

    The supply voltage + 5V comes to this output. We need this voltage to power the MP515 Power Module. Actually, such a connection will allow us to power the entire circuit both from the microUSB input of the sensor itself, and from the miniUSB input of the power module. This will be useful when installing this scheme.

    The connection diagram of the fan to the power relay can be seen in Fig. 7


    Fig. 7

    If you need to manually control the supply ventilation, together with the power module, you can use the MK324 wireless control kit, Fig. 8.

    MK324 is a set of four channel transmitter and receiver, 433 MHz band. The remote control is powered by a 12V battery, 23A series. The operating time from one element is at least 1 year. The receiver is rated for 5V. The range of the kit is 30m. This is quite enough for use in a private house or apartment. Since only one control channel will be involved in the wireless module, the free ones can be used to control lighting or other electrical appliances.


    Fig. 8

    This kit is installed without much effort on a regular place provided in the MP515 power relay. After such a simple modification, it will be possible to forcibly turn on the supply ventilation with a yellow indication of the CO2 sensor.
    An option for installing a fan, ventilation, can be seen in Fig. 9.


    Fig. 9

    Video of the complete system can be seen here:



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