USB relays

Control separately 16 signal relays through a PC by using a standard USB connection and a simple text-based serial protocol.
Each relay can switch up to 3A at 24VDC (warning : this board is not designed for AC current).
There is no need for a separate power supply to power the board, it is designed to be fully powered by the USB connection (that's why small relays are used).

Communication protocol

• The board provides an USB serial port with the following settings : 115200 bits/s, no parity, 1 stop bit.
• All commands are ASCII-only to allow to easily use the board with a simple serial port terminal like Putty, minicom, picocom, etc. If you plan to send commands manually, enable local echo and send CRLF when pressing enter key (see below). Here is an example picocom command invocation : picocom --echo --omap crcrlf -b 115200 /dev/ttyUSB0.
• All commands start with the character #. This way, if you mess up and write the commands into an UNIX terminal, they will be interpreted as comments.
• All commands end with CRLF characters (\r\n), so you only have to press enter key to send the command to the board.
• All commands sent to the board return an answer, the board will ignore all other commands while it is processing the current one. This allows to throttle a fast PC sending too much commands at a time, it must wait for each command answer before sending the next one.
• If you don't know the board state (for instance, the PC rebooted while it was sending a command and the board has received an incomplete command and is stuck waiting for the remaining part of the command), send the ! character at any time. The board will immediately clear its reception buffer.

Commands list

Use the #H<CR><LF> command to display the following list of commands :

Commands :
  - Get a relay state : #Gxx
    'xx' is the relay ID, from 1 to 16.
  - Display this help : #H
  - Set led state : #Lv
    'v' is the led state value (0 to turn off, 1 to turn on, 2 to make it blink).
  - Set relay state : #Sxxv
    'xx' is the relay ID, from 1 to 16.
    'v' is the relay state value (0 to clear, 1 to set).
  - Get firmware version : #V

Photo gallery

Casing plates

Plates are made of 4mm-thick 304 stainless steel.

PCB

PCB top :

PCB bottom :

Assembled PCB

Assembled PCB top :

Assembled PCB bottom :

Casing assembly

Screwing the bolts on the casing lower steel plate :

Fixing the PCB :

Fixing the casing upper steel plate :