Ingredients
NavUp
NavLeft NavRight

Ingredients

This page shows the ingredients for building a Remote Phosphor “Light Bulb”.

MCPCB+LED

The small thing at the bottom is the blue LED. It needs to be thermally tied to the heat sink and also requires two electrical connections.

The star-shaped board makes it easy to accomplish both tasks. It is a Metal Core Printed Circuit Board (MCPCB) which consists mainly of a thick aluminum base. A sandwich of a thin insulation layer, the copper pattern and a top mask layer is bonded to the aluminum.

After the LED is soldered to the board using solder reflow, the result is a sturdy assembly.

HeatsinkFinsUp
HeatsinkLEDSurface

The heat sink shown above is designed specifically for LED light fixtures. It is intended to be mated with the forced air cooler shown below.

This is the flat surface to which the LEDs, better say, the MCPCBs are mounted.

Cooler

The cooler is remarkable device. A vibrating membrane is inside the cylindrical section driven by low power electronics. Air bursts exit the chamber through multiple small holes which are aligned with the gaps of the heat sink.

The amount of air is small but the bursts move at a high speed. Remember Mr. Venturi who said that the pressure in moving air is lower than the pressure of the surrounding space. This causes lots of additional air being entrained by the bursts.

Heatsink+Cooler

We see how the cooler mates with the heat sink. It is fascinating to observe the air flow when the cooler is powered.

One can select three levels of cooling flow. At the highest level, the membrane vibration is definitely audible but the assembly can dissipate 24 Watts.

At the lowest level, the “silent” mode, the sound is practically non-existent but the cooling capacity is still 16 Watts.

The seven LEDs in our design are driven with 700 mA at 3.1 Volts giving off about 15 Watts. Therefor the silent mode was selected.

HeatsinkWithLEDs

We are testing the Remote Phosphor method with two light fixtures, one with two “heads” for a hallway, the other with four “heads” for the foyer.

The photo to the left shows the LEDs with heat sink and cooler fastened to a wooden arm. The wires are hidden in a channel within the arm.

We could power up the LEDs now but there is a dire warning. It would take only seconds to cause permanent eye damage. The LEDs were covered while the assembly was powered up briefly for testing purposes.

MixingChamber

The purpose of the mixing chamber is to contain and remix the rays emerging form the LEDs and the reflected rays from the walls and the remote phosphor disk.

Ideally, the mounting surface of the LEDs should be reflective too. The reflection and diffusion of all surfaces should be a s close to 100% as possible. Commercial mixing chambers will be available in the near future. Meanwhile, I went the cheap route and re-machined a PVC pipe adapter from the home improvement store.

Being less than ideal, there is some loss of light and the color temperature increased slightly.

RemotePhosphor

This is the actual remote phosphor disk. The material comes in various shapes and color temperatures. Since the application is for light fixtures used indoors, I selected the warm-white type (2,700K).

LEDHeadAssembled

Here, everything comes together and two or four of the arms are ready to be attached to a utility box that contains the drive electronics

[Home] [Introduction] [Ingredients] [Electrical Design] [Assembly] [Sources]