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Digital IO - CURRERA current logic


All Digital Inputs and Outputs are located on System Port.

Digital Outputs (GPO1-4)

Isolated open collector outputs, low side switched outputs.
Each Digital OUTPUT has an open collector (sink driver) with common emitters (Digital Output common GND (DO_GND)) for all four Digital OUTPUT signals.
In most cases a power source for external device must be provided.
CURRERA can supply users with 5V power output (Digital Outputs +5V source), which should not be used for external devices with power consumption greater than 60mA.
For example it can be used for a pull-up resistor on Digital OUTPUTs.
To get voltage level logic, external pull ups are needed.
Each of the sink drivers is capable of driving at 100 mA.

When a Digital OUTPUT signal is ON, Digital OUTPUT is closed to DO_GND. When a Digital OUTPUT signal is OFF, Digital OUTPUT is floating.

Connecting devices to CURRERA

The exact connection between CURRERA R, the external device and its power source depends on the type of external device.

  • NPN-compatible device: All devices with an input that is enabled when it is grounded.
    A NPN-compatible PLC device does not provide power for the connected device (sinking input).
  • PNP-¬≠compatible device: all forms of external devices that are programmable logic controllers with PNP transistor types. A PNP-compatible device has an input that is enabled when it receives a voltage (sourcing input).
  • Transistor-transistor logic (TTL): These devices expect the connected device to provide the necessary voltage. For this purpose Digital Outputs +5V source, connected to pull-up resistors on Digital OUTPUT pins, can be used.
  • Inductive load: This category includes all devices that have an inductor wiring, such as small motors or relays. This type of devices requires requires external electronic and must not be connected directly to GPO

Connecting Digital OUTPUT to a NPN-compatible device

To connect CURRERA to a NPN­- compatible device, connect device ground to Digital Output GND.
The Digital OUTPUT signal must be connected to the device's sourcing input.

Connecting Digital OUTPUT to a PNP-compatible device

For this type of device you need to connect the external resistor between a Digital OUTPUT signal and the power supply voltage.
Beware that Digital OUTPUT can sink only 100mA.
If 5V is enough, Digital Outputs +5V source can be used.
All other signals should be connected according to the image below.
For this type of device the logic will be inverted.

Connecting Digital OUTPUT to a TTL device

To connect CURRERA to a TTL device you need to connect the external resistor between a Digital OUTPUT signal and a 5V power source.
For this purpose Digital Outputs +5V source can be used.
TTL devices require a sourcing device to be connected to their inputs.
The external resistor assures that, when the Digital OUTPUT output is set to OFF 5V will occur on the TTL device input.
When set to ON, 0V will occur on TTL device.
This will cause inversion in logic.

Connecting Digital OUTPUT to an inductive load

Do not connect inductive load directly to CURRERA Digital OUTPUT. Transistor have to be used to prevent damage of output.
See image below for proper connection.
Rp resistor can be connected to Digital Outputs +5V source to provide necessary bias current for transistor.
You should also use external diode to protect transistor from over voltage while disconnecting inductive load.

 Long wires can behave like inductive load. 

 !! Beware that only 100mA can Digital Output sink. 
Other wise Digital OUTPUTs may be damaged !! 

Keep in mind that this connection has an inverted logic.
Current will flow trough load at start of CURRERA.

To get positive logic you can use second bipolar transistor.

Or a combination with MOS-FET transistor.

Maximum ratings

V open 24V DC - Maximum open switch voltage
I sink 100mA - Maximum sink current per output
I source 60mA - Maximum current load on Digital Outputs +5V source

Digital Inputs (GPI1-4)

Comply with IEC 61131 - 2

Logic levels
LOGIC 0 I<0.5mA (U<5V)
LOGIC 1 I>5mA (U>11V)

Maximum ratings:

I in - 12mA
U in - 24V

Digital Output +5v source

5v source can provide power for devices which consumption does not exceed 60mA.
For example can be used for pull-ups when voltage level logic is required (TTL), or LED is connected to Digital OUTPUT (see example of usage)

 Do not connect power source to Digital Output +5v source 

Maximum ratings:

I source - 60mA

Example of usage

Connecting LED

To connect LED You can use Digital Output +5v source for powering it.
Sourced current must not exceed 60mA
To calculate appropriate serial resistor you can use following equation:
R = (Vsource - Vd -0.7V)/Id
Where Vsource is Voltage of used source in this particular case it is 5V.
Vd is forward voltage of used LED. (For red diode it may be about 1.3V)
Id is desired current trough LED.
For red LED with forward current 10mA you will need resistor with resistance about 300 Ohm.
You can use common values 270 or 330 Ohm.

See Handling of Digital Outputs in xiAPI

Connecting Button to Digital Input

To use button you need to connect button between voltage source 7-42V and Digital INPUT.
You need also connect Digital Input GND to ground of used voltage source.

See Handling of Digital Inputs in xiAPI

Connecting Button to Digital Input with debounce

Most buttons generate voltage spikes when depressed or released.
To overcome this problem, there is need to add debouncing circuit as on the following scheme.

Or setup internal debounce for CURRERA inputs.

See Debounce of Digital Inputs in xiAPI