Control of ISCE014A, 8 relay module, using its asynchronous serial port, with Bolt 18F2550 system


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Figure 1: The ICSE 014A module is a versatile and sophisticated circuit for remote control of 8 relays. Among its facilities is the ability to connect -via an asynchronous serial port with TTL levels- to a microcontroller system. Activation of the relays is performed by means of a simple protocol, which is described below. In this project, test programs were performed with Bolt 18F2550 system.


Figure 2:  to operate the ICSE 014A module, connect the devices as shown in the photo. The maximum consumption of the module is 700 ma (with all relays activated). We recommend using an external source regulated to 5.5 volts to power the board and avoid overloading the voltage of 5 volts from the USB port on the computer, since USB 2.0 ports only provide up to 500 mA.

Important note: on powering up the ICSE014A board, all relays are activated automatically by the firmware, that is, consumption will be the maximum.


Figure 3. To perform the final tests, a small board with witness leds connected to the contacts of each relay is implemented. The test program turns consecutively on and off each of the relays, with visual check on the LEDs.













Connection for serial communication:

Only a 2-wire connection (GND and TX) via the asynchronous serial port is required. The RX signal is optional and allows for connection confirmation.

In the ICSE014A card, the GND and RX signals are used, as shown in the photo.

The following is a test program. You must load the hex executable file to the Bolt board. With delays of 200 ms The program turns on consecutively each of the 8 relays, wait 3 seconds, and deactivates each of the relays.





Communications protocol:

Based on the figure, after reset to both devices (you may power them up simultaneously), the microcontroller must send the code 50H, which is the initial key for communications. The ICSE014A responds with ACH. This code (50H) is sent only once.

From this moment on, every time you need to modify the status of any or some of the relays, the microcontroller will send the 51H byte first, followed by the desired bit code to activate or deactivate each relay (K1..K8) as shown in figure.

The communication must be 9600 bps. The format is asynchronous and with TTL levels, the start bit is a low level and stop bits in high level.