EPOS4: Connecting a potentiometer to an analog input

Topic:

• How has a potentiometer to be connected to an EPOS4 (or IDX) analog input?

Additional notes:

The following information refers to the EPOS4 and IDX but might be valid for other maxon controllers too. There is just the EPOS4 mentioned as the most popular representative in the following. 

• The analog inputs of the EPOS4 and IDX can measure and process signal voltages of up to +/-10V differential. Please check the specified input voltage range in case of other controller types by the corresponding "Hardware Reference".
• A 5V output voltage like present by solution 1 is not present by an IDX. Therefore one of the solutions 2 or 3 (using an external supply voltage for the potentiometer) has to be chosen.
• If there is an external supply voltage in use (like by solution 3), please check the specified "Max. input voltage" mentioned in the Hardware Reference of your controller. Ensure that the external supply voltage applied to the potentiometer does not exceed the specified "Max. input voltage" value of the analog input.
  Remark:
  The analog inputs of the EPOS4 and IDX are specified for a "Max. input voltage" of +/-24V. Nevertheless the differential analog input which can be measured is just +/-10V.
• If you are not sure about your wiring or it seems not to work like expected, please submit a support ticket and provide the following information to us:
  • Sketch or some photos showing your wiring.
  • Supply voltage in use (in case of solution 2 or 3). 
  • *.dcf configuration file of the EPOS4 or IDX
    -> EPOS / IDX: Export of parameter configuration in a *.dcf file

Technical background:

The analog inputs of the EPOS4 are so-called differential+/-10V, i.e. there is an "AnIN+" and "AnIN-" connection present. Both(!) have to be connected to measure and process an external signal voltage.

Example of the internal hardware in case of an analog input of an EPOS4:
(see chapter "3.3.8 Analog I/O (X8)" of the "EPOS4 50/5 Hardware Reference")

The measured differential analog signal input voltage can be checked by object 0x3160/01 (Analog Input 1) resp. 0x3160/02 (Analog Input 2) of the EPOS4 and IDX.

Solution 1:

If a voltage range of 0 ... 5V is sufficient, the simplest way is to use the 5V output voltage of the EPOS4 for the potentiometer supply too. The wiring looks like this then:

Remarks:

• The 5V auxiliary output voltage is present by the EPOS4's digital I/O connector (e.g. X7/8). 
• It is recommended to use a potentiometer with typically 1 kOhm, 4.7 kOhm, or 10 kOhm. This results in a current draw by the potentiometer of just 5 ... 0.5 mA which means not too much additional load to the limited output current of the 5V output.  
• There is no 5V output voltage available by the IDX. The supply voltage of the potentiometer has to be provided externally like shown by solution 2 and 3 then.
  
  

Solution 2:

If the a I/O or logic supply voltage is in use to power the potentiometer, the wiring can look like this:

Remarks:

• If there is an external supply voltage in use (like by solution 3), please check the specified "Max. input voltage" mentioned in the Hardware Reference of your controller. Ensure that the external supply voltage applied to the potentiometer does not exceed the specified "Max. input voltage" value of the analog input.
• The analog inputs of the EPOS4 and IDX are specified for a "Max. input voltage" of +/-24V. Nevertheless the differential analog input which can be measured is just +/-10V.
  
  

Solution 3:

If there is a +/-10V voltage is present by an external device, the wiring can look like this:

Cross Reference:

Please find some more information concerning the configuration of analog velocity or current commanding of EPOS4 and IDX by the following linked Support Center document:

• EPOS4 / IDX: Analog set value commanding