Some of the most common hardware mistakes 

 October 26, 2023

By  Peter

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Table of contents

I’ve taught electronics for over ten years and have been practicing most of my life.

A few days ago, a student contacted us about one of my drone courses to tell us about his very subtle hardware issue. The drone he built was working perfectly. One day, one of the motors started playing up, causing the drone to do “interesting flips”.

After a few days of troubleshooting, he found the issue: the telemetry module (a transmitter) had moved too close to one of the EMC (Electronic Motor Controller) units after a hard landing. The EMC controls the motor. It seems that due to the proximity between the devices, the telemetry module’s electromagnetic radiation interfered with the EMC’s operation. All this student had to do was to move the telemetry module back to its original position, and the problem was solved.

This story made me think about all the countless hardware issues that I or students in my courses have had to deal with. I have seen a lot of hardware mistakes, from live and exposed LiPo battery terminals to exploding capacitors.

I decided to brainstorm and list some of the more common hardware mistakes I have experienced or people told me about. I also Google around for additional inspiration. You can find my list of errors below. Some of these errors are obvious and perhaps superficial, but I wanted to make this list as complete as possible. I hope you will help me add more to the list (just add your mistakes via the chat at the bottom of the list)!

I recorded this video when I was working on the updated drone course. The drone is pitching right because of an incorrectly connected GND wire. This wiring mistake took me two weeks to fix.

Loose Contacts in Breadboards and Wiring

Soldering Errors

Soldering is the process of joining electronic components to a circuit board. Errors in soldering can lead to unreliable circuits or even permanent damage to the components.

Cold Joints

A cold joint occurs when the solder doesn’t fully melt, leading to a weak electrical connection. This usually happens if the soldering iron isn’t hot enough or if it’s not applied long enough. To correct this, reheat the joint until the solder flows freely.


Bridging happens when too much solder is applied, connecting adjacent pins or traces and causing a short circuit. To fix, use a solder wick to remove excess solder and separate the bridge.

Component Placement Mistakes

Component placement is critical for the circuit’s functionality. Incorrect placement can cause malfunction or damage. These mistakes are more common when working with small components because of the difficulty of seeing tiny placement markers on the package.

Wrong Orientation

Components like diodes, capacitors, and ICs have a specific orientation. Placing them incorrectly can cause damage. Check component markings for proper orientation.

Pin Confusion

Misidentifying pins can lead to wrong connections. Double-check pin numbers and types (analog, digital, PWM) before connecting.

Lack of Protection Measures

Specific components and arrangements require protective measures to function correctly and safely.

No Decoupling Capacitors

Decoupling capacitors smooth out voltage fluctuations. Failing to use them can cause instability. Add a 100nF capacitor between the power and ground near ICs.

No Current-limiting Resistors

Using LEDs or other components without a current-limiting resistor can damage them. Use an appropriate resistor to limit the current.

Overheating Issues

Heat management is crucial in electronic circuits to prevent component failure or fire hazards.

Lack of Heat Sinks

Some components generate heat and require heat sinks for dissipation. Failing to use heat sinks can cause overheating and failure. Attach heat sinks to hot components. Motor driver ICs often benefit significantly from heat sinks.

Poor Ventilation

Enclosing the Arduino and components without proper ventilation can cause overheating. Provide ventilation holes or fans in enclosed projects.

Misusing External Components

Incorrect use of external devices like motors and sensors can lead to circuit damage or incorrect data.

Incorrect Motor Wiring

Connecting a DC motor directly to a microcontroller pin can damage the pin. Use a motor driver or relay for controlling motors.

Sensor Misconfiguration

Incorrectly wired or set-up sensors produce incorrect readings. Refer to data sheets or guides for proper sensor setup.

Ignoring ESD Precautions

Electrostatic discharge (ESD) can damage sensitive electronic components. Proper handling and storage are essential for component longevity.

No Ground Strap

Failing to ground oneself when handling sensitive components can introduce static electricity, risking damage. Use an ESD wrist strap for protection.

Unprotected Storage

Storing components without ESD-safe packaging can expose them to static damage. Use ESD-safe bags for storage.

Incorrect Grounding in Circuits

The issue of incorrectly connecting ground (GND) points in a circuit is a common mistake that can have far-reaching consequences on circuit behavior and performance. All ground connections of a circuit must be connected to a common reference ground.

Ground Loops

Connecting multiple ground points inappropriately can create ground loops, leading to unwanted noise and interference in the circuit.

Signal Integrity

Incorrect grounding can adversely affect the signal integrity, resulting in distorted or noisy signals, thereby impacting the performance of sensitive components like sensors and ADCs.

Component Failure

Grounding mistakes can sometimes cause components to be exposed to voltages or currents outside their tolerable range, leading to component failure.

Power Issues

Incorrectly grounded circuits can result in uneven power distribution, causing some components to receive less power than required for optimal performance.

How to Correct

  1. Single Point Ground: Where possible, connect all ground points to a single, common ground. This minimizes the potential for ground loops and ensures stable voltage references.
  2. Ground Planes: Use ground planes in PCB designs to ensure a consistent and low-resistance ground path.
  3. Star Grounding: In analog circuits, consider using a star grounding technique, where each ground connection has its own path to a central ground point, to reduce interference between components.
  4. Check Connections: Always double-check your ground connections during both design and testing phases to ensure that all components are properly grounded.

Understanding the importance of correct grounding and implementing best practices can go a long way in improving circuit reliability and performance.

Loose contacts, whether on a breadboard or in wiring between components, are a prevalent yet easily overlooked mistake.

Intermittent Failures

Loose connections can lead to intermittent circuit failures that are difficult to diagnose, wasting valuable troubleshooting time.

Signal Degradation

Contacts that are not securely made can result in increased resistance, leading to signal degradation and power losses.

Component Damage

In extreme cases, loose contacts can cause arcing, generating heat and potentially damaging the components or the breadboard itself.

Unreliable Prototyping

For those using breadboards for prototyping, loose contacts can result in unreliable test results, potentially leading to flawed design conclusions.

How to Correct

  1. Secure Connections: Always ensure that wires and component leads are securely inserted into the breadboard or connected to terminals.
  2. Visual Inspection: Regularly inspect connections to identify any that may have become loose over time.
  3. Test Continuity: Use a multimeter to test the continuity of connections, ensuring they are solid and reliable.
  4. Quality Materials: Use high-quality breadboards and jumper wires to ensure a more reliable connection.
  5. Soldering: For long-term projects or critical connections, consider soldering components instead of using a breadboard.

By paying attention to the quality of connections and regularly inspecting and testing your setup, you can minimize the issues that arise from loose contacts, improving both the reliability and performance of your circuits.

Incorrect Application of Test Equipment

The improper use of test equipment like oscilloscopes, multimeters, and logic analyzers is a common mistake that can lead to inaccurate measurements and faulty conclusions.

Misinterpretation of Data

Using test equipment incorrectly can produce misleading data, leading you to make incorrect assessments about your circuit’s performance.

Component Damage

Inappropriate application of test equipment can sometimes lead to excessive currents or voltages being applied to components, causing them to fail.

Time Wastage

Incorrect measurements can lead you down the wrong troubleshooting path, wasting time that could have been better spent resolving the actual issue.

Calibration Errors

Not calibrating or zeroing out your test equipment can lead to offset errors, making even accurate measurements unreliable.

How to Correct

  1. User Manual: Always consult the user manual for any test equipment to understand its proper usage and limitations.
  2. Calibration: Regularly calibrate the equipment to ensure its measurements are accurate.
  3. Probes and Leads: Use the correct types of probes and leads and ensure they are in good condition.
  4. Safety Measures: Always follow safety guidelines, such as turning off power to a circuit when connecting test equipment, to prevent accidental damage.
  5. Skill Development: Invest time in learning how to properly operate and interpret the data from your test equipment, possibly through courses or tutorials.

By understanding how to correctly apply and interpret test equipment, you can improve the efficiency of your troubleshooting efforts and make more accurate assessments of circuit behavior and performance.

Incorrect Power Supply

The power supply is crucial for the functioning of any electronic system. Incorrect power can cause immediate or latent damage. Mistakes in this category make up a significant part of all mistakes in electronics.

Voltage Mismatch

Typical microcontroller circuits operate on 5V or 3.3V. Connecting a 5V component to a 3.3V supply can cause the component to malfunction, and in some cases damage it.

The reverse is worse. Connecting a 3.3V component to a 5V supply without some type of conversion circuitry will most likely damage the component.

Check voltage requirements and connect components to the appropriate power pins.

Reverse Polarity

Connecting the power supply in the wrong orientation can damage the circuit. Double-check the polarity before connecting the power supply. Components like electrolytic capacitors and many integrated circuits are vulnerable to reverse polarity.

Overloading Outputs

Integrated circuit pins have specific current and voltage limitations. Exceeding these limits can damage the board or connected components.

Current Overdraw

Microcontroller pins have a maximum output current. For example, Arduino pins can supply up to 40mA of current. Exceeding this can damage the pin. Use external power for high-current loads.

Voltage Overload

Using components requiring higher voltage than the Arduino pin can supply can cause poor performance. Use level shifters or external power for such components.

Incorrect Circuit Connections

Correct circuitry is fundamental for a project. Errors in connections can lead to erratic behaviour or damage.

Floating Pins

Unconnected input pins are susceptible to noise, causing unpredictable behaviour. Connect them to a known voltage level through a resistor.

Short Circuits

Directly connecting power to the ground can cause excessive current flow and damage. Double-check connections to avoid this.

Software-Hardware Mismatch

Incompatibilities between software and hardware can cause malfunctions or prevent the program from running altogether.

Library Incompatibility

Using an incompatible library can lead to malfunctions or compilation errors. Verify library compatibility with your board.

Incorrect Board Selection

Choosing the wrong board in the Arduino IDE (or any other IDE) can lead to upload failures or erratic behaviour. Select the correct board type in the IDE.

Communication Errors

Proper communication between devices is vital for multi-component systems. Mistakes can lead to data loss or corruption.

Wrong Baud Rate

A mismatch in baud rates between hardware and software causes communication issues. Set the same baud rate on both ends.

Lack of Pull-up/Pull-down Resistors

In I2C and SPI communications, the absence of pull-up or pull-down resistors can lead to erratic data transmission. Use appropriate resistors as per the protocol specifications.

Issues with Long Copper Traces Acting as Antennas

Long copper traces on a PCB can unintentionally act as antennas, leading to electromagnetic field (EMF) interference in your circuit.

Unintended Radiation

These traces can emit electromagnetic waves when carrying high-frequency signals. This not only affects the circuit itself but can also interfere with nearby electronic devices.

Signal Integrity

Long traces are more susceptible to picking up external electromagnetic interference, leading to noise and reduced signal integrity.


In circuits with multiple long traces running parallel to each other, one trace can induce a signal in another, leading to crosstalk. This phenomenon degrades the performance of the circuit by introducing unwanted signals.

Compliance Issues

Unintended radiation from traces can lead to the device failing electromagnetic compatibility (EMC) tests, which are often a requirement for commercial products.

How to Correct

  1. Shorten Traces: Where possible, keep copper traces as short as possible to minimize their ability to act as antennas.
  2. Ground Planes: Use a ground plane to shield the traces and minimize EMF emission.
  3. Impedance Matching: Proper impedance matching can minimize reflections and reduce the chances of the trace acting as an antenna.
  4. Trace Routing: Route critical signal traces away from potential sources of interference.
  5. EMI Filters: Use EMI filtering techniques to block high-frequency noise.

Understanding the antenna-like behavior of long copper traces and taking corrective measures can mitigate issues related to EMF interference, improving both the circuit’s performance and its compliance with EMC standards.

Electrical Noise from Motors

Electrical noise generated by motors is a frequently overlooked issue that can cause havoc in sensitive electronic circuits.

Signal Interference

Motors can generate electrical noise that propagates through a circuit, affecting sensitive components like sensors and microcontrollers. This noise can distort signal readings and cause unreliable system behavior.

Data Corruption

In digital systems, the electrical noise from motors can lead to data corruption or intermittent faults, making debugging a challenge.

Reduced Component Lifespan

Over time, the spikes and transients generated by motor noise can degrade electronic components, leading to a reduced lifespan for your hardware.

Regulatory Challenges

In severe cases, the electrical noise generated can be significant enough to cause a device to fail EMC compliance tests, preventing its commercial release.

How to Correct

  1. Isolation: Physically isolate motors from sensitive components to limit the impact of noise.
  2. Filtering: Use capacitors, inductors, or ferrite beads to filter out noise at the motor terminals.
  3. Shielding: Utilize shielded cables for carrying signals that are susceptible to noise.
  4. Separate Power Supplies: Where feasible, use separate power supplies for motors and sensitive electronic components to minimize noise propagation.
  5. Optical Isolators: In extreme cases, consider using optical isolators to separate noisy motor circuits from sensitive electronics.

Being aware of the electrical noise issues that motors can introduce allows for preemptive measures to be taken, thus improving the reliability and performance of the overall system.

Electrical Interference from Fast-Switching Devices

Fast-switching devices like CPUs and microcontrollers can introduce a significant amount of electrical noise into a circuit, affecting its overall performance.

Signal Distortion

The high-frequency noise generated by these fast-switching components can distort analog and digital signals, leading to data errors and poor system reliability.

Interference with Nearby Components

High-frequency noise can also couple into nearby traces or components, causing unintended interactions and crosstalk.

Power Supply Noise

These devices can introduce noise into the power supply lines, which can then propagate to other parts of the circuit.

Regulatory Issues

In some cases, the electrical noise produced can lead to the device failing regulatory compliance tests, such as EMC tests.

How to Correct

  1. Low-Pass Filters: Implement low-pass filters on critical signal paths to remove high-frequency noise components.
  2. Grounding and Shielding: Employ proper grounding techniques and use shielded cables to minimize the propagation of electrical noise.
  3. Decoupling Capacitors: Place decoupling capacitors close to the power supply pins of the fast-switching device to provide a noise-free power source.
  4. Physical Separation: Place noise-sensitive components away from fast-switching devices to minimize electromagnetic coupling.
  5. PCB Layout: Optimize the PCB layout to minimize the length of traces that can act as antennas, thus reducing the emission and reception of high-frequency noise.

Being aware of the potential for electrical noise from fast-switching devices and taking appropriate corrective measures can help maintain signal integrity and ensure compliance with regulatory standards.

What have I missed?

If you have a hardware mistake that should be on this list, please let me know via the comments below.

About the image

This image was generated by DALL·E 3. The prompt I used was “create an image of a battery misconnected to a circuit. The circuit emits colourful sparks as a result of the connection mistake. Add smoke.” I continue to be amazed by what this technology can do.



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