DIY LED Tester & Power Supply Upgrade Guide

If you're interested in DIY low-power adjustable power supplies or LED testers, this article is worth a read.

This LED tester/low-power adjustable power supply requires the following upgrades:

1. Replace the potentiometer with a WH148.

2. Upgrade to dual-mode: constant voltage and constant current.

3. Redesign the internal layout for better enclosure fitting.

4. Replace the charging board with a TP4056 module that combines protection and charging.

There's still room for optimization on this LED tester:

1. Upgrade the potentiometer to a 3296 long-shaft version.

2. Replace the voltmeter with a combo voltmeter/ammeter.

3. Replace the fixed current-limiting resistor with an adjustable one.

4. Limited internal space restricts further upgrades.

5. Due to the built-in battery protection board, it cannot output high current. However, you can bypass this by using it while charging or removing the battery protection and relying on the charging board’s protection instead.

Component List:

· 3048 3.7V battery

· Charging board

· Boost converter

· 10kΩ potentiometer

· 2.2kΩ resistor

· Enclosure

· Banana jacks

· Power switch and mounting screws

Overview:

1. The main external components include a voltmeter, power switch, mode switch, banana jacks, and potentiometer. It's as slim as a Xiaomi fitness band—quite amusingly compact!

2. The internal layout and wiring require many short jumper wires.

3. Function Demonstration:

· Constant Voltage Mode

· Constant Current Mode

4. Working Principle:

(1) When no LED is connected, the circuit acts as a series connection between the voltmeter and resistor. Since the voltmeter has high resistance, it shows nearly the full output voltage, allowing you to check the adjustable voltage range.

(2) When an LED is connected, the resistor and LED are in series, and the voltmeter is connected in parallel with the LED. In this case, the voltmeter displays the voltage drop across the LED after it lights up.

Note: There is a minor schematic error — the power switch should be placed on the positive line between the charging board and the boost converter. Please adjust accordingly.