Quality Assurance Engineer, PLC Automation

ON.energy is setting the standard for large load interconnection. ON’s patented AI UPS™ is a medium-voltage UPS that serves as a firewall, protecting the data center from the grid, and the grid from the data center. With multiple gigawatts currently under construction, we are enabling grid-safe data centers.

The Quality Assurance Engineer is responsible for hands-on experience in PLC programming, industrial protocol testing, and Python-based test automation. Skilled in designing and executing functional and integration test cases across PLC platforms and communication protocols.

Key Responsibilities:

• Design, develop, and execute Unit tests, functional, integration, and regression test cases for PLC-based control systems
• Write and maintain Python-based automated test scripts for testing PLC I/O, HMI interfaces, and communication protocols
• Develop, review, and validate PLC code (Ladder Logic, Function Block Diagram, Structured Text) across Siemens S7-1200/1500
• Collaborate with controls engineers to define acceptance criteria and validate system requirements
• Identify, document, and track defects using tools such as Azure Devops or equivalent; lead root cause analysis for critical failures
• Conduct Hardware-in-the-Loop (HIL) and Software-in-the-Loop (SIL) testing where applicable
• Produce clear test plans, reports, and traceability matrices aligned with release timelines
• Required Experience & Skills
• University degree in Software Engineering, Computer Science, Quality Engineering, or a related technical field.
• 5+ years of hands-on experience in PLC programming and testing across Siemens platform.
• 5+ years of experience building and maintaining automated test frameworks using pytest or equivalent python framework.
• 3–5 years of experience with Siemens TIA Portal for PLC development, diagnostics, and commissioning support.
• Experience designing and executing functional and integration tests, including test case development, defect tracking, and validation of fixes.
• Working knowledge of industrial communication protocols such as S7, Modbus TCP/RTU, and OPC-UA.
• Preferred Experience
• Proficiency in automated unit testing the PLC Logic
• Experience with SCADA systems
• Familiarity with Agile / Scrum methodologies in industrial settings
• Knowledge of functional safety standards such as IEC 61508 / IEC 62061
• For US-based roles - What you’ll get: Competitive salary + annual performance-based bonus eligibility
• Medical, dental, and vision insurance
• 401(k) with company match
• Paid time off and company holidays
• For Mexico-based roles - What you’ll get: Competitive salary + annual performance bonus eligibility
• Christmas Bonus (Aguinaldo): 30 days
• Major medical expenses and life insurance
• Paid time off and holidays (per local policy)
• For all roles: Professional development and growth opportunities
• Opportunity to grow with a mission-driven team shaping the future of clean energy
• Equal Opportunity: ON.energy is committed to equal employment opportunity and to maintaining a work environment free of harassment, discrimination, or retaliation.
• Benefits vary by role and location and are subject to change.
• Agency Notice: ON.energy does not accept unsolicited resumes from staffing agencies, search firms, or third-party recruiters. Resumes submitted without a fully executed Master Services Agreement (MSA) and a written request from an authorized member of our Talent Acquisition team will be considered the property of ON.energy. No placement fees or compensation will be paid for unsolicited candidate submissions.