Electrical Rules Check (ERC) in PCB Design - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding ERC Purpose

What is the main purpose of performing an Electrical Rules Check (ERC) in PCB design?

A To check the mechanical dimensions of the PCB for fitting in the enclosure.

B To generate the bill of materials for component purchasing.

C To optimize the PCB for thermal management and heat dissipation.

D To verify that the PCB layout matches the schematic connections and detect electrical errors.

💡 Hint

Think about what errors ERC is designed to catch related to electrical connectivity.

ERC is used to verify that the schematic's electrical connections are correct and to find issues like unconnected pins or conflicting connections.

❓ dax_lod_result

intermediate

Identifying ERC Error Count

Given a PCB design tool that outputs ERC errors as a table with columns: ErrorType and Count, which DAX expression correctly calculates the total number of ERC errors?

PCB Design

ERC_Errors = SUM(ERC_Table[Count])

A ERC_Errors = DISTINCTCOUNT(ERC_Table[ErrorType])

B ERC_Errors = COUNTROWS(ERC_Table)

C ERC_Errors = SUM(ERC_Table[Count])

D ERC_Errors = AVERAGE(ERC_Table[Count])

💡 Hint

Think about how to sum all error counts, not just count rows or distinct types.

Summing the Count column gives the total number of errors across all types.

❓ visualization

advanced

Best Visualization for ERC Error Types

You want to create a dashboard showing the distribution of different ERC error types and their counts. Which visualization type best communicates this information clearly?

A A stacked bar chart showing error counts by error type.

B A pie chart showing the percentage of each error type out of total errors.

C A scatter plot mapping error severity versus error count.

D A line chart showing error counts over time.

💡 Hint

Consider which chart type clearly compares counts across categories.

A stacked bar chart clearly shows counts per error type and allows easy comparison between them.

🔧 Formula Fix

advanced

Debugging ERC Error Filtering

In a report, a filter is applied to show only 'Short Circuit' ERC errors, but the report still shows other error types. Which DAX filter expression correctly filters only 'Short Circuit' errors?

PCB Design

FILTER(ERC_Table, ERC_Table[ErrorType] = "Short Circuit")

A FILTER(ERC_Table, ERC_Table[ErrorType] == "Short Circuit")

B FILTER(ERC_Table, ERC_Table[ErrorType] = "Short Circuit")

C FILTER(ERC_Table, ERC_Table[ErrorType] != "Short Circuit")

D FILTER(ERC_Table, ERC_Table[ErrorType] = Short Circuit)

💡 Hint

Check the correct syntax for string comparison in DAX.

DAX uses a single equals sign for comparison and strings must be in quotes.

🎯 Scenario

expert

Scenario: Prioritizing ERC Errors for Fixing

You have a list of ERC errors with columns: ErrorType, Severity (High, Medium, Low), and Count. You want to create a calculated measure that sums counts only for High severity errors to prioritize fixing. Which DAX expression achieves this?

A HighSeverityErrors = SUMX(FILTER(ERC_Table, ERC_Table[Severity] = "High"), ERC_Table[Count])

B HighSeverityErrors = CALCULATE(SUM(ERC_Table[Count]), ERC_Table[Severity] = "High")

C HighSeverityErrors = SUM(ERC_Table[Count]) WHERE ERC_Table[Severity] = "High"

D HighSeverityErrors = SUM(ERC_Table[Count]) IF ERC_Table[Severity] = "High"

💡 Hint

Think about how to filter rows before summing in DAX.

SUMX with FILTER correctly sums counts only for rows where Severity is High.

Practice

1. What is the main purpose of Electrical Rules Check (ERC) in PCB design?

easy

A. To generate the bill of materials automatically

B. To check the physical dimensions of the PCB

C. To find electrical mistakes like unconnected pins early in the schematic

D. To simulate the circuit's electrical behavior

Solution

1. Step 1: Understand ERC's role in PCB design

   ERC is used to detect electrical issues such as unconnected pins or conflicting connections in the schematic.

2. Step 2: Differentiate ERC from other checks

   Physical dimension checks and simulations are separate processes, not part of ERC.

3. Final Answer:

   To find electrical mistakes like unconnected pins early in the schematic -> Option C

4. Quick Check:

   ERC = Find electrical mistakes early [OK]

Hint: ERC finds electrical errors in schematics before layout [OK]

Common Mistakes:

• Confusing ERC with physical layout checks
• Thinking ERC simulates circuit behavior
• Assuming ERC generates manufacturing files

2. Which of the following is the correct way to run an ERC in most PCB design software?

easy

A. Click the 'Run ERC' button after completing schematic edits

B. Export the schematic as PDF and review manually

C. Run a 3D visualization of the PCB

D. Generate Gerber files before running ERC

Solution

1. Step 1: Identify the ERC execution method

   Most PCB tools have a dedicated 'Run ERC' button or menu option to start the electrical rules check.

2. Step 2: Eliminate incorrect options

   Exporting PDFs, 3D visualization, and generating Gerber files are unrelated to running ERC.

3. Final Answer:

   Click the 'Run ERC' button after completing schematic edits -> Option A

4. Quick Check:

   Run ERC via dedicated button [OK]

Hint: Run ERC using the software's dedicated button [OK]

Common Mistakes:

• Thinking ERC runs automatically without user action
• Confusing ERC with file export or visualization
• Running layout checks instead of ERC

3. After running ERC, you see an error: Pin 'IN' on U1 is unconnected. What does this mean?

medium

A. The pin 'IN' is connected correctly and no action is needed

B. The pin 'IN' is connected to multiple nets causing a short

C. The component U1 is missing from the PCB layout

D. The pin named 'IN' on component U1 has no wire connected to it

Solution

1. Step 1: Interpret the ERC error message

   The message says the pin 'IN' on component U1 is unconnected, meaning no wire or net is attached to it.

2. Step 2: Understand implications

   An unconnected pin usually indicates a missing connection that may cause circuit malfunction.

3. Final Answer:

   The pin named 'IN' on component U1 has no wire connected to it -> Option D

4. Quick Check:

   Unconnected pin means no wire attached [OK]

Hint: Unconnected pin means no wire attached to that pin [OK]

Common Mistakes:

• Assuming unconnected means short circuit
• Confusing missing PCB part with schematic connection
• Ignoring ERC errors thinking they are warnings

4. You ran ERC and got multiple errors about conflicting pin connections. Which step should you take to fix this?

medium

A. Ignore the errors and proceed to PCB layout

B. Check the schematic for pins connected to multiple nets and correct wiring

C. Delete the entire schematic and start over

D. Run a 3D model check instead

Solution

1. Step 1: Analyze ERC conflict errors

   Conflicting pin connections mean pins are wired to more than one net, which is invalid.

2. Step 2: Correct schematic wiring

   Review and fix the wiring in the schematic to ensure each pin connects to only one net.

3. Final Answer:

   Check the schematic for pins connected to multiple nets and correct wiring -> Option B

4. Quick Check:

   Fix wiring conflicts in schematic before layout [OK]

Hint: Fix wiring conflicts in schematic, don't ignore ERC errors [OK]

Common Mistakes:

• Ignoring ERC errors and continuing
• Deleting schematic unnecessarily
• Confusing ERC errors with layout issues

5. You have a complex schematic with multiple power nets. ERC reports a warning that a power pin is connected to a net with a different voltage level. What is the best approach to resolve this?

hard

A. Verify the power net assignments and ensure pins connect only to nets with matching voltage levels

B. Ignore the warning if the circuit works in simulation

C. Connect all power pins to a single net regardless of voltage

D. Remove the power pins from the schematic

Solution

1. Step 1: Understand power net voltage warnings

   ERC warns when a power pin connects to a net with a different voltage, which can cause damage or malfunction.

2. Step 2: Verify and correct net assignments

   Check that each power pin connects only to the correct net matching its voltage level to avoid conflicts.

3. Step 3: Avoid unsafe shortcuts

   Ignoring warnings or connecting all power pins to one net can cause serious issues.

4. Final Answer:

   Verify the power net assignments and ensure pins connect only to nets with matching voltage levels -> Option A

5. Quick Check:

   Match power pins to correct voltage nets [OK]

Hint: Match power pins only to nets with correct voltage [OK]

Common Mistakes:

• Ignoring ERC voltage warnings
• Connecting different voltage nets together
• Removing essential power pins