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8 Relay 8 Analog USB IO Controller 24 V

8 Relay 8 Analog USB IO Controller 24 V

The KTB-225 is a USB or RS-485 controlled IO module for interfacing PCs to real world applications, such as controlling lights and sprinkler systems, reading sensors and monitoring switches or analog signals. The Relays are capable of switching up to 5 A at 250 VAC, 10 A at 120 VAC and 10 A at 24 VDC but the PCB tracks will only handle up to about 5 A. A simple ASCII protocol allows control from Windows/Mac/Linux using either USB Virtual COM drivers or RS-485. Additionally, multiple devices can be connected to one RS-485 bus, allowing control of many devices from one USB port.

The KTB-225 has relays with 24 VDC coils and requires an 18 to 28 VDC supply. The KTA-225 has 12 V relays and requires a 9 to 15 VDC supply but is otherwise identical.

This controller is based on the hardware of the KTA-223 controller, but the number of analog inputs has been increased at the cost of the digital inputs. It can be programmed as a stand-alone controller using the free, open source Arduino environment. Internally, the controller is “shield compatible”, allowing the use of many extension boards designed for the Arduino Deumilanove. As shipped the controller is loaded with a sketch or program that receives simple commands over the USB or RS-485 serial port and switches relays or responds with the status of the analog inputs.

Multiple controllers can be connected to one or more PCs in an RS-485 network. Each controller can be assigned an address and will respond to commands addressed to them.


  • 8 Relay Outputs 5A 250VAC
  • 8 Analog Inputs (10 bit)
  • Connections via Pluggable Screw Terminals
  • 0 to 5 V, 0 to 3.3 V or 0 to 20 mA Analog Inputs, Jumper Selectable
  • 5A Relay Switching
  • Power Indicator LED
  • All enclosed in Professional looking plastic case
  • Arduino Compatible
  • Accepts Arduino Shields (Ethernet / XBee)
  • USB Virtual Serial Port or RS485 Input
  • Easily connect multiple units far apart by RS485

New in Version 3:

The newly revised KTx-225 have just arrived! As of mid December, we're shipping out version 3 of the KTx-225. It's fully compatible with the previous versions, but has a range of new features including:

  • New relays with higher contact to coil isolation voltage for safer switching of loads
  • Power, Tx and Rx Leds Visible from the outside of the box
  • Redesigned serial and USB circuitry and layout for higher baudrates, better reliability and better noise immunity
  • Changes to the layout inside to match the changes made with the Arduino Uno

An example program has been written and VB express 2010 to show you how to interface with the KTA-225 using a PC.

Web Interface Sketch

Using the WebUi sketch and an Ethernet shield allows you to control the Relays and read the Analog Inputs from a web browser


Download Manual

Download Schematic

Download Arduino Sketch

SoftI2cMaster Arduino Library by William Greiman (for use with SFC-010, requires SCL_PIN to be 13 and SDA_PIN to be 12)

VB Express 2010 Test Software

VB Express 2010 Test Software & Source

Delphi Light Flasher Software & Source

Time-A-Relay software (5th May 2010)

WebUi Sketch (requires Ethernet Shield)


SKU:  KTB-225

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Qty. Price
(AUD ex. GST)
1 to 4 $199.00
5 to 9 $179.10 (10% off)
10+ $169.15 (15% off)