Build Your Own 5V LED Tester with 30mA

Circuit diagram:

Description

This uncomplicated LED analyzer comprises a current supply featuring a variable resistor allowing for current modification. The current supply is realized utilizing a specific TL081 operational amplifier. The output current of this amplifier flows through the diode and R2. The voltage decline across R2 is returned to the inverse input and evaluated against the reference voltage, which is established with R1 and applied to the direct input.

The adjustable range is roughly 0–30 mA, proving suitable for testing virtually all standard LEDs. Optionally, a multimeter can be connected across the LED to measure the voltage present on the LED. For the power source, a small bench power supply, with its output voltage set to 5 V, represents a sensible choice. It’s advantageous to incorporate a potentiometer with a scale to provide a visual indication of the current flowing through the LED. To refine the scale’s accuracy, a temporary ammeter can be substituted in place of the LED.

Operational Amplifier (TL081)

The TL081 is a versatile and widely employed operational amplifier. It is a three-terminal integrated circuit – one power supply input, one output, and one input. This particular amplifier is commonly used in analog circuits due to its low input bias current, low input offset current, and high open-loop gain. It is frequently found in instrumentation, audio circuits, and general-purpose amplification applications. The TL081 offers good stability, making it suitable for a broad range of circuit designs. Its performance characteristics make it a reliable choice for applications demanding precise current control and signal amplification.

Diode

A diode is a semiconductor device that allows current to flow primarily in one direction. It’s a fundamental component in many electronic circuits. Typically, diodes are formed from a silicon-base material with a thin layer of a different semiconductor material (like Germanium or Indium Antimonide) to create the depletion region which controls the current flow. In this circuit, the diode serves as a one-way valve for the current, ensuring that it only flows from the positive side of the power supply through the LED, preventing reverse current flow. The specific diode used here is likely a standard silicon diode, often characterized by its forward voltage drop and reverse leakage current.

Resistors

Resistors are passive electronic components that oppose the flow of electric current. They are characterized by their resistance, measured in ohms (Ω). In this circuit, R1 and R2 are resistors, each offering a specific resistance value. R1 is used to establish the reference voltage, while R2 controls the current flowing through the LED. The values of these resistors are carefully chosen to ensure proper operation of the circuit and to provide the required current and voltage levels for testing LEDs. The specific values are essential for the correct functioning of the LED tester circuit. They are commonly made of carbon composition, metal film, or wirewound materials.