Advanced Troubleshooting
Finding faults in systems with hardware, software and sensors all working together.
The question
Your weather station logged perfectly for three days, then started missing readings at night. Is it the battery, the wiring, the sensor or the program?
What you’ll discover: how technicians track down faults in complex systems: signal tracing, known-good references, isolating hardware from software, catching intermittent faults and keeping good records.
In simple terms
BeginnerSame method, bigger system
The method from Lesson 17 still works: check power first, look carefully, consider the usual suspects, then measure and split the problem in half. In a system with a microcontroller and sensors, add one more question early on: is this a hardware problem or a software problem?
A quick way to tell: run the simplest possible test program, like the blink program from Lesson 24, or a program that only reads and prints one sensor. If the simple test works, the hardware for that part is probably fine and the fault is likely in your main program.
Techniques technicians use
- Signal tracing: follow the signal from its source toward its destination, checking it at each stage (with a meter, a scope or print statements), until it goes missing.
- Known-good comparison: compare with a working unit, a fresh part, or the reference measurements you recorded when it worked. That’s why you write readings down on a good day.
- Substitution: swap in a known-good part, such as a different sensor, cable or battery pack, one at a time.
- Print statements and logs: make the program report what it’s doing and what it reads, so you can see where it goes wrong.
Go deeper
IntermediateIntermittent faults
Faults that come and go are the hardest. They often follow a pattern, so record exactly when they happen and what else was going on:
- Temperature: a joint or connector that opens up only when cold (common outdoors in an Alberta winter) or warm.
- Movement: a loose breadboard wire or cracked solder joint. Gently wiggle wires while watching readings.
- Power: a battery that sags under load at night, or a power bank that switches itself off (see the Digital Thermometer).
- Moisture: condensation inside an enclosure overnight.
- Software timing: a counter that overflows, a file that grows too large, or memory that slowly fills.
AdvancedDocumenting faults
Professionals keep a fault log: the date, the symptom, what was tested, what was found, what was changed, and whether it fixed the problem. It stops you repeating tests, helps the next person, and often reveals patterns over weeks or months.
Change only one thing at a time, and after a fix, test long enough to be sure: an intermittent fault that usually appears every few days isn’t fixed just because it didn’t appear in the first hour. Finally, ask why it happened, not just what failed, so the design can be improved (Lesson 39).
Quick check
What simple test helps separate hardware from software problems?
Run the simplest possible test program, such as blink or reading one sensor.
What is signal tracing?
Following a signal from its source toward its destination, checking at each stage until it goes missing.
Why keep a fault log?
To avoid repeating tests, help others, and reveal patterns in faults over time.
Words to know
- Signal tracing
- Following a signal stage by stage to find where it’s lost.
- Known-good
- A part or unit known to work correctly, used for comparison.
- Intermittent fault
- A fault that comes and goes.
- Fault log
- A record of symptoms, tests, findings and fixes.
Electronics School is part of the Discovery Zone. Every activity here runs on small batteries or a USB cable: never wall outlets. The one plug-in tool is the optional soldering iron, set up by an adult.