Universal Robots Forum

Electrical interfaces

(This post is a Wiki, experienced developers can modify the content)

This post describes the electrical interfaces of a Universal Robot, UR3, UR5 or UR10.
There are electrical interfaces (analog and digital) in the controlbox and at an M8 connector at the tool.

Control box

  • 16 digital inputs (0/24V DC)
  • 16 digital outputs (0/24V DC)
  • 2 analog inputs (0-10V DC or 4-20 mA, 12 bit, differential)
  • 2 analog outputs (0-10V DC or 4-20 mA, 12 bit, differential)

The internal 24V PSU can supply a maximum current of 2A total. An external 24V PSU can optionally be used to increase power.

Tool connector

M8 connector.
Suited for: Lumberg RKMV 8-354

  • 2 digital inputs
  • 2 digital outputs
  • 2 analog inputs (0-10V DC or 4-20 mA, non-differential)

Tool digital signals and power supply can be set to either 12V or 24V mode collectively.
Max. current drain is 600 mA.

Any digital input can be configured in PolyScope software or via the URScript interface, to have a functionality to be an external Play, Pause, Stop or Freedrive button.

Dear Jacob,
thanks for sharing data on electrical interfaces. A couple of questions about this:

  • Is the 600 mA limitation a continuos or peak value? What is the other value?
  • What is the maximum duration of the peak value?
    Thanks and Best Regards.

The constant current drain of the tool is 600 mA.
A peak above this should be no longer than 1 ms.
The actual peak current capability is not rated.

This is valid for both CB2 and CB3 robots.

Any digital input other than the configurable inputs can be configured to by a play/pause/stop/freedrive input. It would be nice if those could be configured as well

Any control box input can be set up for this, including the tool inputs.


I cannot see a way to set configurable inputs to these functions like I can standard and tool inputs. Here is a screenshot of a standard digital input where it shows the IO Action dropdown menu

That is missing from the configurable input options

Am I doing something wrong?


@jbm is not clear to me from both this post and the UR5 manual whether the max current drain of the tool (600mA) is related only to the internal power supply (which provides a global upper limit of 2A), or it is a strict limitation even if an external power supply is connected to the system, which raises the the maximum absorption up to 6A.

As you can imagine, our end-effector requires more than 600mA.

Alessandro Tondo @qbrobotics


The combined max. current draw from the Tool connector is 600 mA.
The 12 V or 24 V power at the tool is generated locally on the Tool, and has nothing to do with the power in the Control box. Hence an external PSU does not change this limit.

In the controlbox there is an internal PSU with a cap of 2 A total, combined for all 24 V terminals and outputs.
You can skip this PSU, and use an external 24 V supply as specified in the User Manual, where the max. allowed current through the control box terminals is 6 A.

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I am developing an end-effector, and was wondering if there are any more detailed electronic schematics of the connector/arm internals?
Thank you.

Electrical diagrams are available here.


Thank you for the quick reply. I had a look at the link you sent me. Is it possible to get a more detailed description of the internal structure of the Tool_Mounting_Bracket that appears on page 5 of UR3_schmatic_drawings_rev3.0.3.1.pdf?

What information are you looking for for the documentation of the electrical interfaces of the Tool connector?

Thank you again for your swift reply.
I am interested in knowing the exact schematics of the circuits making up the DI and DO connectors, if possible.

I sadly do not have these diagrams available, however note that the DI’s are PNP-based inputs, and the outputs are NPN-based outputs.

Regarding the tool connector all the pins are dedicated to their originally purpose I suppose?

It is not possible to remove jumpers in the control cabinet and connect a different set of I/Os to the other end of the tool connector cable?

That is not possible.
The signale are not passed up in the arm, but are generated locally on the Tool PCB.

5 posts were split to a new topic: UR robot with battery supply