Check polarity, resistor, voltage and connection continuity. The procedure below focuses on decisions you can apply immediately while building or troubleshooting a circuit.
Key rules
- A reversed LED will not light at typical low voltage.
- An oversized resistor can reduce current below visible output.
- Measure voltage directly across the diode.
Step-by-step procedure
- Write down required voltage, current, tolerance and operating conditions.
- Verify connections and datasheets before applying power.
- Power up with current limiting and measure defined test points.
- Record actual values and conclusions in the project journal.
Practical example
Assume a circuit runs from 5 V. Rather than choosing a part by appearance, calculate the required value, check power and absolute ratings, then compare the result with a real measurement. This avoids repeating the same fault.
Common mistakes
- Mixing units or prefixes.
- No electrical or thermal margin.
- In-circuit measurement without accounting for parallel paths.
For mains voltage, high current or stored energy, use appropriate procedures and qualified help. LutujTo does not replace manufacturer documentation.
FAQ
Where should I start?
A reversed LED will not light at typical low voltage.
What should I check before power-up?
Measure voltage directly across the diode.