This IoT 24-channel low-power signal relay controller is capable of hosting many types of IoT communication modules, including Particle Photon, Electron, Arduino, and more.  On-board SPDT relays are ideally suited for low-power signal switching applications, up to 1 Amp at 12VDC.  NCD SPDT relay controllers have three connection terminals for user-access to each relay.  We use high-quality Omron relays with a low on-resistance between contacts.  Designed primarily for resistive or mildly capacitive low-power signals, the on-board relays in this design focus on signal integrity, making it an ideal choice for telecommunications and low-power audio switching applications.

This controller is based on dual MCP23017 controllers, a common I2C interface chip for GPIO applications.  In this design, the GPIO port is used to control 24 on-board SPDT relays.  Eight programmable Digital Input/Output port pins are also available via screw terminals for use in Contact Closure detection applications or monitor and control external TTL circuits.  The I2C bus support up to 8 similar devices (based on the MCP23008 or MCP23017).  This controller counts as two devices on the I2C bus.  Two on-board address jumpers set the I2C start address of both MCP23017 interface chips.  On-board status LEDs display the on/off status of each relay.  This controller may be powered using our optional power supply or with 12VDC and direct screw terminal connection of bare power wires.  Each relay is accessible to the user via screw terminals, capable of accepting 14 AWG wire.