# UR5 safety wiring issue: Dedicated E-stop inputs fail, configurable safety inputs work **URL:** \ **Category:** Technical Questions\ **Created:** [May 26, 2026, 9:12am UTC](https://forum.universal-robots.com/t/ur5-safety-wiring-issue-dedicated-e-stop-inputs-fail-configurable-safety-inputs-work/42803 "2026-05-26T09:12:55Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![dawidnojman2004](https://avatars.discourse-cdn.com/v4/letter/d/dfb087/32.png) [@dawidnojman2004](https://forum.universal-robots.com/u/dawidnojman2004)\ **Post date:** [May 26, 2026, 9:12am UTC](https://forum.universal-robots.com/t/ur5-safety-wiring-issue-dedicated-e-stop-inputs-fail-configurable-safety-inputs-work/42803/1 "2026-05-26T09:12:55Z")
Hello, I am working with a UR5 robot and I have a question regarding safety wiring and dedicated safety inputs. I have a safety setup where a safety relay controls auxiliary relays, and these auxiliary relays then control interposing relays before going to the robot: Safety relay → Auxiliary relays → Interposing relays → UR5 I use the interposing relays because I want to keep the robot wiring separated from other components in the electrical cabinet. This was also a requirement in the project to avoid mixing internal robot signals with other system signals. When I connect the safety signals to the dedicated Emergency Stop inputs (EI0 and EI1), I get the fault: “Ports did not disconnect simultaneously” However, when I connect the exact same signals to Configurable Safety Inputs configured for safety, everything works without any issue. Some details: - Two-channel safety wiring is used - EI0 and EI1 are wired separately - SI0 and SI1 remain bridged if unused - The issue only occurs on the dedicated E-stop inputs - The configurable safety inputs work correctly - I am currently using standard auxiliary/interposing relays because all safety relay outputs are already occupied My questions are: 1. Can the dedicated EI0/EI1 inputs be more sensitive to timing differences between channels than configurable safety inputs? 2. Could the auxiliary/interposing relays introduce enough delay to trigger “Ports did not disconnect simultaneously”? 3. Is it acceptable to use Configurable Safety Inputs as the main robot safety interface from a safety relay? 4. Would using configurable safety inputs affect the robot’s safety level (PLd / Cat3)? 5. Has anyone experienced a similar issue with UR5 safety wiring? Any advice would be appreciated. Thank you. ---
**Author:** ![davide.tomelleri](https://avatars.discourse-cdn.com/v4/letter/d/eb9ed0/32.png) [@davide.tomelleri](https://forum.universal-robots.com/u/davide.tomelleri)\ **Post date:** [May 26, 2026, 11:30am UTC](https://forum.universal-robots.com/t/ur5-safety-wiring-issue-dedicated-e-stop-inputs-fail-configurable-safety-inputs-work/42803/2 "2026-05-26T11:30:41Z")
hi, try to see this article. [Universal Robots - Connecting an Emergency Stop Device vs. a Safeguard Protective Device](https://www.universal-robots.com/articles/ur/application-installation/connecting-an-emergency-stop-device-vs-a-safeguard-protective-device/) ---
**Author:** ![dawidnojman2004](https://avatars.discourse-cdn.com/v4/letter/d/dfb087/32.png) [@dawidnojman2004](https://forum.universal-robots.com/u/dawidnojman2004)\ **Post date:** [May 26, 2026, 12:21pm UTC](https://forum.universal-robots.com/t/ur5-safety-wiring-issue-dedicated-e-stop-inputs-fail-configurable-safety-inputs-work/42803/3 "2026-05-26T12:21:43Z")
Thanks. But can I use the configurable input as the main external emergency connection? Without loosing the safety rating. I can’t use the dedicated emergency input because the fault I’m getting. ---
**Author:** ![davide.tomelleri](https://avatars.discourse-cdn.com/v4/letter/d/eb9ed0/32.png) [@davide.tomelleri](https://forum.universal-robots.com/u/davide.tomelleri)\ **Post date:** [May 26, 2026, 2:19pm UTC](https://forum.universal-robots.com/t/ur5-safety-wiring-issue-dedicated-e-stop-inputs-fail-configurable-safety-inputs-work/42803/4 "2026-05-26T14:19:35Z")
you can configure the configurable input as you need, also for emergency stop ![image](https://us1.discourse-cdn.com/flex020/uploads/universal_robots/original/2X/a/a2d73fe6a4dc1a14914c96d8a432264b764915cf.jpeg) ---
**Author:** ![dawidnojman2004](https://avatars.discourse-cdn.com/v4/letter/d/dfb087/32.png) [@dawidnojman2004](https://forum.universal-robots.com/u/dawidnojman2004)\ **Post date:** [May 26, 2026, 3:22pm UTC](https://forum.universal-robots.com/t/ur5-safety-wiring-issue-dedicated-e-stop-inputs-fail-configurable-safety-inputs-work/42803/5 "2026-05-26T15:22:45Z")
Does it give it the same PL and Cat safety rating? ---
**Author:** ![davide.tomelleri](https://avatars.discourse-cdn.com/v4/letter/d/eb9ed0/32.png) [@davide.tomelleri](https://forum.universal-robots.com/u/davide.tomelleri)\ **Post date:** [May 28, 2026, 8:43am UTC](https://forum.universal-robots.com/t/ur5-safety-wiring-issue-dedicated-e-stop-inputs-fail-configurable-safety-inputs-work/42803/6 "2026-05-28T08:43:13Z")
well… I suppose yes, because there is no reason that will be different. for sure you can ask to UR support. ---
**Author:** ![efn](https://avatars.discourse-cdn.com/v4/letter/e/35a633/32.png) [@efn](https://forum.universal-robots.com/u/efn)\ **Post date:** [May 28, 2026, 8:59am UTC](https://forum.universal-robots.com/t/ur5-safety-wiring-issue-dedicated-e-stop-inputs-fail-configurable-safety-inputs-work/42803/7 "2026-05-28T08:59:06Z")
1. Can the dedicated EI0/EI1 inputs be more sensitive to timing differences between channels than configurable safety inputs? 2. Could the auxiliary/interposing relays introduce enough delay to trigger “Ports did not disconnect simultaneously”? 3. Is it acceptable to use Configurable Safety Inputs as the main robot safety interface from a safety relay? 4. Would using configurable safety inputs affect the robot’s safety level (PLd / Cat3)? 5. Has anyone experienced a similar issue with UR5 safety wiring? 🙂 ---
**Author:** ![dawidnojman2004](https://avatars.discourse-cdn.com/v4/letter/d/dfb087/32.png) [@dawidnojman2004](https://forum.universal-robots.com/u/dawidnojman2004)\ **Post date:** [May 28, 2026, 12:11pm UTC](https://forum.universal-robots.com/t/ur5-safety-wiring-issue-dedicated-e-stop-inputs-fail-configurable-safety-inputs-work/42803/8 "2026-05-28T12:11:49Z")
Thanks for answering my questions.