---
title: Smooth Robotics ApS Retrofit Kit
description: "The Smooth Robotics Retrofit Kit lets you connect any power source to your Universal Robots arm using digital I/O signals. It is compatible with any power source that supports 2-step torch trigger operation. ![Retrofit Kit components](https://hub.smooth-robotics.com/wp-content/uploads/2026/09/manual-power-sources-retrofit-kit-components.webp) ## Step 1: Install…"
url: "https://hub.smooth-robotics.com/docs/power-sources-retrofit-kit/"
updated: "2026-09-23"
category: Power Sources
---

# Smooth Robotics ApS Retrofit Kit

The Smooth Robotics Retrofit Kit lets you connect any power source to your Universal Robots arm using digital I/O signals. It is compatible with any power source that supports 2-step torch trigger operation.

![Retrofit Kit components](https://hub.smooth-robotics.com/wp-content/uploads/2026/09/manual-power-sources-retrofit-kit-components.webp)

## Step 1: Install the connector plate in the UR control box

1. Remove the side panel of the UR control box.
2. Insert the adapter plate from the inside of the control box.
3. Mount the plate from the outside using the existing screws.

![Adapter plate inserted into the UR control box](https://hub.smooth-robotics.com/wp-content/uploads/2026/09/manual-power-sources-retrofit-kit-step1-plate.webp)

1. Plug in the **blue input cable** to the first digital input terminal on the UR control box.
2. Plug in the **red output cable** to the third digital output block on the UR control box.

Note

Each cable only fits its intended port and cannot be installed incorrectly.

![Blue and red cables plugged into the UR control box terminals](https://hub.smooth-robotics.com/wp-content/uploads/2026/09/manual-power-sources-retrofit-kit-step1-cables.webp)

## Step 2: Install the current clamp

1. Mount the current clamp on the welding cable.

Important

The **red dot** on the current clamp must face the torch.

Alternatively, mount the clamp on the earth cable — in that case the red dot must face the power source.

1. Insert the other end of the cable into one of the ports on the connector plate.

![Current clamp mounted on the welding cable](https://hub.smooth-robotics.com/wp-content/uploads/2026/09/manual-power-sources-retrofit-kit-step2-clamp.webp)

## Step 3A: Install the adapter cable (Euro connector)

1. Attach the **euro connector** to the power source.

![Euro connector attached to the power source](https://hub.smooth-robotics.com/wp-content/uploads/2026/09/manual-power-sources-retrofit-kit-step3a-euro-connector.webp)

1. Connect the other end of the adapter cable to the remaining port on the connector plate.

![Euro adapter cable connected to the connector plate](https://hub.smooth-robotics.com/wp-content/uploads/2026/09/manual-power-sources-retrofit-kit-step3a-adapter.webp)

1. Connect the hose package to the power source.

![Hose package connected to the power source](https://hub.smooth-robotics.com/wp-content/uploads/2026/09/manual-power-sources-retrofit-kit-step3a-hose.webp)

Note

If you have a water-cooled power source with disconnected coolant lines, reconnect them before continuing.

Tip

When using the euro connector, it is recommended to replace the liner in the hose package with one long enough to extend through the newly installed connector.

## Step 3B: Install the adapter cable (US connector)

1. Plug the US connector into the power source.

![US connector plugged into the power source](https://hub.smooth-robotics.com/wp-content/uploads/2026/09/manual-power-sources-retrofit-kit-step3b-us-connector.webp)

1. Connect the other end to the available port on the connector plate.

![US adapter cable connected to the connector plate](https://hub.smooth-robotics.com/wp-content/uploads/2026/09/manual-power-sources-retrofit-kit-step3b-adapter.webp)

Warning

The power source must be configured to **2-step** mode. See your power source manual for instructions.

## Step 4: Add the Retrofit Kit in SmoothTool X

With the hardware in place, add the digital I/O integration in SmoothTool X.

Tap **SmoothTool X Settings** from the Application view. In the sidebar, under **Components**, tap **Power Sources**, then tap **Add new power source**.

 ![Power Sources page with the Add new power source button](https://hub.smooth-robotics.com/wp-content/uploads/2026/09/manual-power-sources-retrofit-kit-power-sources-tab.webp)

In the **Add power source** dialog, select the **Independent Integrations** tile and choose the **Retrofit Kit** model, then tap **Add power source**.

 ![Add power source dialog — Retrofit Kit selected](https://hub.smooth-robotics.com/wp-content/uploads/2026/09/manual-power-sources-retrofit-kit-add-power-source.webp)

### Configure the Retrofit Kit

Configure the digital I/O signals:

| Field | Description |
| --- | --- |
| Input | The input line that carries the feedback shunt (arc detection) signal. Enable its checkbox to activate the feedback shunt, then pick the line — **DI** (controller digital input) or **CI** (configurable input) — and its number. |
| Output | The output line SmoothTool X uses to start and stop welding. Pick **DO** (controller digital output) or **CO** (configurable output) and its number. |

Tip

If DI0 and DO0 are already used by other equipment, select the prefix and number of the I/O lines you actually wired to.

When done, tap **Done** to save the power source.

 ![Retrofit Kit digital I/O configuration page](https://hub.smooth-robotics.com/wp-content/uploads/2026/09/manual-power-sources-retrofit-kit-configuration.webp)

### Select the Retrofit Kit

Back on the **Power Sources** page, expand the new entry and tap **Selected** to make it the active power source. The Retrofit Kit communicates over digital I/O rather than a network connection, so there is no separate connect step.

 ![Configured Retrofit Kit power source entry](https://hub.smooth-robotics.com/wp-content/uploads/2026/09/manual-power-sources-retrofit-kit-power-source-entry.webp)

The Retrofit Kit is now connected and SmoothTool X is ready for welding.

## Programming with SmoothTool X and the Retrofit Kit

The Retrofit Kit is driven entirely over digital I/O: SmoothTool X switches the arc on and off with the configured output and reads the feedback shunt on the configured input. It has no welding parameters of its own — no wire feed speed, voltage or job — so a weld node shows no **Power source** tab for it.

What it does have is arc timing, and that lives with the arc settings rather than with the power source:

- Device-wide defaults are on the **Arc Settings** page, under **Components** in the SmoothTool X Settings sidebar — see [Arc Settings](/docs/usage-guides-arc-settings/).
- A weld node can override them on its own **Arc settings** tab. Arc settings belong to the weld node, and every segment inside it inherits them.

| Identifier | Description |
| --- | --- |
| Wait before arc on | Time the robot waits before the arc is switched on at the start of a weld. |
| Wait after arc on | Time the robot waits after the arc starts before beginning to move. |
| Wait before arc off | Time the robot waits before the arc is switched off at the end of a weld. |
| Wait after arc off | Time the robot waits after the arc is switched off before continuing. |

The arc-feedback settings on those pages (**Arc activation timeout**, **Arc lost timeout**, **Arc deactivation timeout**, **Attempt to restart arc**, **Speed percentage at re-arc**) apply to the Retrofit Kit as well, since the feedback shunt reports whether the arc is live.

## Simulation

The **Simulation** toggle in the Power source popover (opened from the button in the operator screen toolbar) runs the program as a dry run: the robot executes the full program and motion path, but the arc is never started — no weld signal is sent over the digital I/O. Use it to test a program safely, then turn it off to weld for real.