ESCON: Digital Output Wiring

Topic:

• How to wire the digital outputs of an ESCON servo controller?
• What configuration features are available?

Solution:

The ESCON controllers provide two digital outputs. Different predefined functions can be assigned to these digital outputs by ESCON Studio's "Startup Wizard".

Digital outputs: DigOUT3, DigOUT4

The technical specification of the digital outputs can be found in the "Hardware Reference" (-> chapter "Setup / Digital Inputs/Outputs 3 and 4") corresponding to the concrete ESCON product type in use.

Example: "ESCON 50/5" (part.no. 409510):

The internal hardware design of the ESCON's outputs is a so-called "Open Drain" resp. "Open Collector" circuit, i.e. that the output switches to GND but does not(!) supply a voltage by its own.

Typically there is an external pull-up resistor required which supplies the output and the load with the required supply voltage or the load has to be connected in between the ESCON's output (switching to GND) and a supply voltage.

The advantage by this design is that the output resp. load can be supplied to any required voltage level (e.g. 5V, 12V, 24V, within the "Max. input voltage" range specified for the ESCON's digital outputs).

Please find some information about this design by page 30 of maxon's "Formulae Handbook" too:

Wiring examples:

Please note the following five typical wiring examples below:

(1) Switching a LED or signal lamp (max. 36V DC) by an ESCON's  digital output.

(2) Commanding a top-level controller's input (e.g. of a PLC or microcontroller) by an ESCON's digital output.

(3) Switching a relay by an ESCON's digital output.

(4), (5) Commanding an optocoupler by an ESCON's digital output.

Supply voltage of digital outputs and load

The supply voltage applied to the pull-up resistor resp. the load ...

• ... has to be chosen depending on the load's requirements and max. supply voltage specification.
  (e.g. PLC: typ. 24V  /  lamp: typ. 12-24V  /  LED or microcontroller: typ. 3.3V or 5V)
• ... has to be within the specified "Max. input voltage" of the ESCON's output (-> ESCON's "Hardware Reference").

Pull-up resistor

The pull-up resistor has to be chosen in a way (R = U / I) so that the resulting current ...

• ... can fulfill the load's worst case requirements.
• ... does not exceed the specified ESCON's digital output "Max. load current" value (typ. 500 mA, check ESCON's "Hardware Reference").

Commanding an input of a top level controller

If an ESCON output has to command the input of a top level controller (e.g. microcontroller or PLC) like by wiring example (2), ...

• ... the pull-up resistor (typ.  1 ... 10 kOhm) has be connected in between the ESCON's digital output pin and a supply voltage (which has to be chosen depending on the required logic '1' voltage level to command the top level controller's input).
  • In case of a PLC input the required voltage level is typically 24V.
  • In case of a microcontroller or processor the required voltage level might be typically 3.3V or 5V. Please check the microcontroller's hardware specification to apply a proper voltage level to the pull-up resistor. (Caution: A too high voltage level can damage the top-level microcontroller easily!)
• ... the ESCON's output pin has to be connected to the top level controller's input in addition.
• ... the GND of the ESCON, the top-level controller, and the power supply has to be connected.

Configurable output functionality

There are different predefined functions available which can be assigned to each digital output by ESCON Studio's "Startup Wizard":

• Stop:
  "Stop" is a function which is just be available in case of the ESCON's I/O pin is configured as a digital input (and not output). In this case the motor will be stopped (= decelerated) depending on an input signal.
• Ready:
  The function "Ready" signals the operational state ("Ready" resp. "Error") of the ESCON.
• Speed resp. Current Comparator:
  The digital output is activated or deactivated depending on the actual value (i.e. speed resp. motor current) and a configured limit, range, or deviation.
  
  • Limit:
    The signal gets active and stays active as long as the actual value (speed resp. motor current) reaches or exceeds the configured limit value.
  • Range:
    The signal gets active and stays active as long as the actual value (speed resp. motor current) is within the configured value range.
  • Deviation:
    The signal gets active and stays active as long as the actual value is within the specified deviation range around the external or internal set value. It is possible to observe by this function if a drive can actually follow the resulting profile based on an externally commanded set value and internally configured settings like acceleration or deceleration.
• Commutation Frequency:
  This function is just available in case of an EC (= brushless) motor. The digital output provides a frequency which corresponds to the electrical frequency of the motor (= 1 pulse per electrical turn of the motor).
  Hint:
  In case of a multi-pole pair motor this frequency has to be divided by the pole pair number to get the mechanical speed of the motor shaft.

Configurable digital output polarity

The polarity of the digital outputs can be configured by ESCON Studio's "Startup Wizard":

• High active:
  Actuation with positive logic '1' (High)
  => ESCON's "Open Collector" output is conducting to GND (= low impedance) in "Active" state when no error state is present. The supply voltage at the ESCON's output pin is "Low" close to 0V in this case. 
  • Wiring example (1):
    The LED turns on because the current flows through the external pull-up resistor, LED, and ESCON's internal output transistor conducting to GND.
  • Wiring example (2):
    The PLC (resp. microcontroller) detects the GND level (i.e. a logic '0') at its input because the ESCON's internal output transistor is conducting to GND.
  • Wiring example (3):
    The relay is switched on because the current flows through relay's windings and the ESCON's internal output transistor conducting to GND.
  • Wiring example (4):
    The optocoupler is switched on because the current flows through the external pull-up resistor, the LED of the optocoupler, and ESCON's internal output transistor conducting to GND.
  • Wiring example (5):
    The optocoupler is deactivated because the current flows through the ESCON's internal output transistor to GND (and the optocoupler's LED is connected to GND on both sides this way).
    
    
• Low active:
  Actuation with negative logic '0' (Low)
  => ESCON's "Open Collector" output is non-conducting in "Active" state when no error state is present. The current flow through ESCON's internal output transistor is blocked and the voltage level at the ESCON's output pin corresponds almost to the pull-up voltage.
  • Wiring example (1):
    The LED is turned off because the current flow through the LED and ESCON's internal output transistor is blocked (i.e. not connected to GND).
  • Wiring example (2):
    The PLC (resp. microcontroller) will detect the pull-up voltage level (e.g. 24V, i.e. a logic '1') because ESCON's internal output transistor is blocked and the pull-up voltage level is present at the PLC's (or microcontroller's) input this way. 
  • Wiring example (3):
    The relay is switched off because the current flow through the relay windings and ESCON's internal output  transistor is blocked (i.e. not connected to GND).
  • Wiring example (4):
    The optocoupler is switched off because the current flow through the optocoupler's LED and ESCON's internal output transistor is blocked (i.e. not connected to GND).
  • Wiring example (5):
    The optocoupler is activated because the current flow through the ESCON's internal transistor is blocked. The current flows from the pull-up voltage through the external pull-up resistor, and internal LED of the optocoupler this way.