Diodes: what they do and how to use them
Diodes are simple but powerful electronic parts. They let current flow one way and block it the other. That behavior makes them handy for fixing common problems: protecting circuits from reverse polarity, turning AC into DC, detecting signals, and even lighting up your project when you use LEDs.
Common diode types and what they're good for
Start by knowing the usual suspects you’ll meet on a bench:
Rectifier diodes (1N400x series) are cheap and used for converting AC to DC. They handle higher currents but have a larger voltage drop, so they’re fine for power supplies.
Schottky diodes have a lower forward voltage drop and faster switching. Use them when you need higher efficiency or less loss in power circuits.
Zener diodes act like a voltage clamp in reverse. Use them with a series resistor to make simple reference voltages or protect inputs from overvoltage.
LEDs (light-emitting diodes) are diodes that emit light. They need a current-limiting resistor or a constant-current driver. LED forward voltage varies by color: red ~1.8–2.2V, green ~2.0–3.2V, blue/white ~3.0–3.6V.
Photodiodes generate current when light hits them — useful for sensors and remote controls.
Practical tips for building and testing
Polarity matters. The diode’s stripe marks the cathode (negative side) and the other lead is the anode. Put them the right way or nothing will work — or something will burn.
When wiring LEDs, calculate the resistor: R = (Vsource - Vf) / If. Example: with 5V source, a white LED (Vf 3.2V) and 20mA target current, R = (5 - 3.2) / 0.02 = 90Ω (use 91Ω or 100Ω standard value).
To test a diode with a multimeter use the diode test mode. Forward bias should show Vf (around 0.6–0.7V for silicon, 0.2–0.4V for Schottky). Reverse bias should show open or OL. For LEDs the meter may not light them; use a small battery plus resistor to test safely.
Watch power dissipation. P = Vf × If. If that power is significant, add a heatsink or spread the load across multiple parts. For Zener circuits, pick a series resistor that keeps the Zener within its rated power at the worst-case current.
Avoid common mistakes: no resistor on LEDs, ignoring reverse voltage limits, and mixing up diode orientation on PCBs. Breadboard first, then solder once you confirm everything works.
If you want project ideas: build a diode-based reverse polarity protector for batteries, a simple LED indicator circuit for your drone controller, or a tiny Zener reference to stabilize sensor readings. Diodes are small, cheap, and they solve a surprising number of real problems.
Why are LED lights so costly? Is the manufacturing cost so high?
LED lights are four times more energy efficient than traditional incandescent bulbs, and are also longer lasting, making them a popular choice for lighting solutions. However, they tend to be more expensive than other lighting options due to the cost associated with their manufacturing. LED lights are made up of many small parts, including the diodes, circuit boards, heat sinks, and lenses, which all add to the cost of production. Additionally, these lights require more sophisticated production processes which makes them more expensive to produce.
27.01.23
Maverick Renfield
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