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Isolated serial Input/ Output Kit V3 image Zoom

Isolated serial Input/ Output Kit V3

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SKU: QK108
This kit has been designed for remote control and sensing applications. The kit provides 8 Relay outputs and 4 optically isolated inputs. Easy to use text commands to control the device from any TTY program or write your own software.
SKU: QK108

Availability: In stock
Assembly Required: Yes

CA$99.94 Country Flag
Product Description


    K108 serial I/O elctronic kit Click on image to see one in higher resolution
    This kit provides 8 relay outputs (mains rated) and 4 optically isolated inputs. It is designed for control and sensing applications. It can be used in various applications including load switching, external switch input sensing, contact closure and external voltage sensing. It is controlled via a serial port using a variety of methods of control software using a set of simple text commands.

    N1 Turns Relay 1 ON
    F1 Turns Relay 1 OFF
    T1 Toggles Relay 1
    S1 Returns Status of Relay 1
    I1 Returns Status of INPUT 1
    0 ALL command, N0 will turn all relays on
    F0 Turns all relays off

    Connection to the isolated inputs and relay outputs is via "pluggable type" screw terminal blocks by Dinkle.

    Using the serial port has several advantages:
    1. Fewer wires are required (3 instead of 9 or more needed by the parallel port)
    2. Serial cables can be a lot longer (up to 100ft) allowing "remote" control.
    3. Serial ports can be used with any computer and operating system

    The kit is constructed on a double-sided, through hole plated printed circuit board (PCB) and fits in a plastic case measuring 140(W) c 110 (D) x 35 (H)mm. Screen-printed front and rear panels are supplied.

    The kit requires a 12V DC power supply center positive. A wall adaptor rated at 500mA (minimum) is suitable.


    Number of relays 8
    Type Form C, SPDT
    Contact Capacity 15A 24VDC
    Resistive Load 15A 120VAC
    10A 240VAC
    Contact Capacity 5A 24VDC
    Inductive Load 5V 120VAC
    5A 240VAC
    Maximum allowable voltage AC 240V
    DC 110V
    Maximum allowable current 15A
    Maximum allowable power force 1800VAC/250W
    Minimum applicable load 5VDC 10mA
    Relay life (mechanical) 10 million operations
    Relay life (electrical/load dependent) 100,000 operations
    Operating time 10msec maximum
    Number of inputs 4
    Type Polarised, opto-isolated (not TTL/CMOS compatible)
    Voltage 5 - 24 VDC
    Isolation (min.) 2500V peak
    1775V RMS (1 sec.)

    This kit is an extension of our popular QK74, "PC Printer Port Relay Board". The idea was to redesign the PCB to fit into a plastic case and add some inputs as well. At the same time a "latch" was added so that the PC could be switched off without affecting the relays. This proved to be difficult due to the PCs POST (Power On Self Test) function, which would operate and release relays during power up. The easiest solution was to use the serial port.

    The brains of the kit is IC1, and 89C2051 microcontroller from Atmel ( This was chosen because it has the required number of I/O pins and built in serial port. It is preprogrammed to process all commands received via the serial port, control the relays and monitor the inputs.

    IC8 provides conversion between TTL and RS232 signals. IC2 is an octal relay driver, ULN2803A, and is used to drive each of the relays. The opto-couplets, IC4-7, are used to provide electrical isolation between the inputs and the rest of the circuitry.

    At power-up, all relays are off (released). A reset switch is provided for manually turning off all relays.

    Note: during power up relays 1 and 2 momentarily operate. Also, when using the reset switch, these two relays will be operated for as long as the reset switch is pressed. This is due to a characteristic of pins P1.0 and P1.1 of the Atmel microcontroller used.

Additional Information

    Additional Information

    SKU QK108
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