Procedure for Reverse Engineering Electric Components

Procedure for Reverse Engineering Electric Components#

Ben Manning, Purdue University

Last modified: 2025-12-04

Introduction#

Reverse engineering electric components involves analyzing and understanding the design and functionality of an existing electronic device or system. This process can be complex and requires a systematic approach. Below is the general approach that will be followed in ECE 39595. Note that this is a generic procedure and should be adapted as necessary depending on the device that is being analyzed.

Preparation and Safety#

  1. Gather Tools and Equipment: Multimeter, oscilloscope, soldering/desoldering tools, magnifying glass, digital camera, SPICE software, etc.

  2. Safety Measures: Ensure the device is powered off and unplugged. Use anti-static measures to protect components.

    Important! If the device is something with a large power supply, or if you notice that a light stays on for a long time after being unplugged, make sure to wait a few minutes to continue. This is evidence of large capacitors that can store charge and be dangerous if accidentally touched.

Gather Information- DO NOT SKIP!#

  1. Research about the product:

    • What is the general function of the device? (Light bulb, thermostat) How do these devices generally work?

    • What should you expect inside? Are there known sub circuits you should expect to find? (If the device is plugged into the wall, there is likely a rectifier and/or transformers)

    • Are there specific precautions to take when taking apart the device?

Documentation#

  1. Photograph the Device: Take detailed photos of the device from various angles before and after disassembly.

  2. Record Model and Serial Numbers: Document any identifying information on the device.

  3. Take Notes: Document the mechanical design of the enclosure, sensor positions, power connections, and other points about the physical design as you see fit.

Disassembly#

  1. Remove the Enclosure: Carefully open the device, noting the type and placement of screws or clips.

  2. Label Components: As you disassemble: label, sort, and document each component for easier reassembly. It may be worth taking more pictures here to help with documentation and reassembly.

Visual Inspection#

  1. Identify Components: Look for recognizable components such as resistors, capacitors, ICs, transistors, connectors, etc. Do not worry about determining specific component values at this time.

  2. Inspect PCB: Note the layout, traces, and any multi-layer configurations.

Component Identification#

  1. Catalog Components: List all components, including their markings and package types.

  2. Datasheets: Look up datasheets for ICs and other components to understand their specifications and functions.

Functional Analysis and Circuit Tracing#

  1. Understand Sub-circuits: Break down the circuit into functional blocks (e.g., power supply, signal processing, communication…). Create a block diagram/flow chart of the device. Break sub-circuits down further as needed.

  2. Analyze Functions: Study how each block contributes to the overall operation of the device. This may involve researching and simulating different sub-circuits to observe their behavior if you are not familiar with them. If you are having trouble finding information, make sure to ask a colleague.

    For sub-circuits you are more interested in:

  3. Trace Connections: Using a multimeter, trace and document the connections between components.

  4. Create a Schematic(s): Begin drafting schematic diagrams based on your traced connections.

  5. Identify known sub-circuits: As you notice different circuit patterns, such as voltage dividers, filters, bridges, and amplifiers, document them in notes and schematic draft. It may be worth making notes about what their function might be in this specific case. Do not spend too much time exploring sub-circuits you do not know at this point.

Verification#

  1. Compare with Known Designs: Compare your schematic with similar existing designs or reference schematics.

  2. Simulation: Use simulation tools (SPICE) to simulate the circuit’s behavior and validate your schematic.

  3. Replication: Replicate the process done by the device using a microcontroller, timers, or other tools to verify your understanding of the device

Review and Iteration#

  1. Peer Review: Have your schematic and findings reviewed by other colleagues.

  2. Iterate: Make any necessary revisions based on feedback and further testing.

Documentation and Reporting#

  1. Finalize Schematic: Complete a detailed schematic diagram.

  2. Formalize Your Work: Document your findings, including the function of each component and block, signal analysis, and any deviations from expected behavior.

  3. Photographic Record: Include annotated photos of the PCB and components.

Optional Steps#

  1. Signal Analysis:

    1. Power Up (if safe): If possible, power the device on and use an oscilloscope/Multimeter to analyze signals at various points in the circuit.

    2. Establish a Reference Ground: Just like every other time we measure electric circuits, we need a reference for every measurement. In DC, this will likely be the negative terminal of a battery or supply. In AC, this can be a ground lead or the neutral terminal of an AC source. Keep in mind that if you are using the neutral terminal of a source, you will only be observing half of the signal!

    3. Record Behavior: Note the behavior and interaction of components under different operating conditions.

  2. PCB Layout Reconstruction: If needed, reconstruct the PCB layout using PCB design software.

  3. Prototype Building: Build a prototype based on your schematic to further test and validate the design.

This is a generic procedure that provides a structured approach to reverse engineering electric components, which can be adapted based on the complexity and specific requirements of the device in question.

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