Four LED Regulated Lamp

(C) 2017 G. Forrest Cook

This project can be used with a CirKits solar circuit kit.

Regulated 4 LED lamp Regulated 4 LED lamp perf board
Regulated 4 LED lamp lit dimly Regulated 4 LED lamp lit wiring

Regulated 4 LED lamp schematic

Four LED Regulated Lamp


This is a regulated four LED lamp that runs on 12VDC power. The lamp can be used as a night light or as an accent light. It is similar to the Seven Component Regulated Quad LED Lamp, but it features a current-balancing scheme that allows it to be used with multiple LED colors. The version shown in the photo uses two white LEDs, an amber LED and a red-orange LED. When viewed through the lamp's diffuser, the combined color is of a pinkish white hue.


The two 100nF capacitors and the 13 ohm resistor filters out noise on the power supply lines. The LM317L and 33 ohm resistor act as a current regulator that is set to 38mA. the 33 ohm resistor. Current flows from the battery through the regulator, then through the two series LED strings. The voltage drop differs slightly across the red and amber LEDs, causing slightly different current levels in the two LED strings. the 56 ohm series resistors help to balance the current in the two paths.


All of the components were assembled on a small piece of perforated circuit board material. Be careful when soldering the LEDs, excessive heat can damage the parts. Verify that the lamp functions correctly before assembling the lamp fixture parts. The lamp fixture was built using a chrome base and two frosted diffuser lenses from an old metal halide lamp.

The outer diffuser was glued to the metal base with clear Alex Plus caulk and the caulk was allowed to dry for 24 hours. The circuit board was seated inside of the outer diffuser using more caulk. The wires pass through a hole in the metal base. The center diffuser was attached over the circuit board with more caulk. The caulk should be allowed to dry for several days before applying power, uncured caulk conducts electricity.


Connect this circuit to a 12V battery or power supply, be sure to observe the correct polarity. The lamp should light up and The low current draw allows the lamp to run for many hours on a battery. The lamp can be operated continuously. If built in the manner described above, the lamp will be completely waterproof and can be used indoors and outdoors. The lamp will produce a steady brightness from 10-18VDC.

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