Thanks to Mike at RapidLED for donating the 12 LED Plug N Play kit for our evaluation and as a Prize for the February 2012 meeting. RapidLED is a great source for DIY LED builds. Not only do they provide quality parts but they also give you helpful information on how to use the products they sell. We  are proud to recommend RapidLED as a source for your LED needs.

First impression.

I received my order on January 17th. Everything was well packaged and protected and arrived in great shape. Inside the box I found everything I had ordered and a plus. They included a single LED tester so that I could test each LED before assembly. This is a nice touch because it is possible to damage the LEDs during installation if too much heat is applied when soldering the wires to the terminals and once soldered it’s difficult to determine if the LED was DOA or damaged by the end user. The tester allows you to verify that all LEDs arrived in working order. While this isn’t so much an issue with the PNP LEDs because the wires are pre-soldered to the terminals they still included the tester. It’s little things like this that set RapidLED apart from other vendors. Overall I found everything in order and was very happy with my order.

The Build

I began the project by building a Housing to hold the electronic components. I’ll discuss a little about each component as we get to them. One of my primary design goals was to have a fixture that was true to the PnP so that it could simply be mounted above the tank plugged in and used. I didn’t want any parts located remotely from the fixture. Since the heat-sink provided by RapidLED was black anodized I decided to use a black acrylic for the housing and cover for the fixture. The housing would have to hold the LED Driver, a 1o volt dc power supply, the power cord and a potentiometer for the dimming circuit.

This might be a good time to talk about these components. 

The LED Driver is the component in the white housing shown in the picture. LED Drivers are constant current devices that supply the power to the LEDs. I used a Mean Well ELN-60-48D Dimmable Driver. This driver is an excellent driver for running between 8 and 14 LEDs at up to 1.3 Amps. It is important to know the Maximum Rated amperage for the LEDs you will be running. The LEDs I am using in this fixture have a amp rating of between 1 and 1.5A. Exceeding the maximum amperage will severely reduce the life of the LEDs so it is important to adjust the output of the driver to the amperage of the lowest rated LED. In my case 1A. More on this later. This driver also uses a reference voltage of 0 to 10 Volts to control the dimming of the LEDs

10Volt DC Power Supply My kit came with a 120 volt AC to 10 volt DC adapter (The black component on the right side of the housing). This is needed to supply the reference voltage for the Mean Well Driver. A potentiometer is used to adjust this voltage from 0 to 10V and the driver dims the LEDs accordingly.

Potentiomenter A potentiometer is used to adjust the reference voltage to the LED Driver for dimming.

Power Cord  I used an 8′ extension cord for this project.

After building the housing I mounted and installed the components. I used Silicone Rubber to mount the AC adapter and bolted the LED Driver into the place. Next I drilled the holes for the power cord and potentiometer. In order to dissipate the heat from the LEDs I will be using a fan for active cooling. It will be powered by the same AC adapter that supplies the DC voltage for dimming. In order to make the wiring cleaner I picked up a 4 terminal block from Radio Shack and mounted it to the housing. Two of the terminals are DC+ and the other two DC-. Then it was just a matter of connecting the leads from the dimming circuit and the leads to the fan to the appropriate terminals on the block. Click Here for complete wiring instructions and Here for potentiometer circuit instructions.

Heat Sink

LED’s radiate heat differently than other types of lighting. Instead of heat radiating away from the lamp, in an LED the heat radiates back through the base of the LED. This is great for reducing temperatures in the tank but makes dissipating the heat difficult. To handle the cooling of LEDs a heat sink of sufficient size is needed. Active cooling in the form of a fan attached to or blowing across the heat-sink assures that this heat doesn’t build up causing failure of the LED. I chose an oversize heat-sink both for cooling and to act as the main structure of the fixture. 

I was very pleased to find that the black anodized heat sink supplied in this kit had two mounting channels along the top of the fins. This made connecting the completed housing and fan to the heat-sink a breeze.  In this picture you can see the fan mounted to the heat-sink. I drilled holes in the tabs on the sides of the housing and mounted the housing to the heat-sink using these mounting channels as well.

Standard LED Wiring

Up to this point there has been no difference between building a standard DIY fixture and the RapidLED PnP system but now you’re going to see where the PnP components take the work and confusion out of building your own fixture.

 When mounting and wiring a standard LED array you layout your LEDs and then daisy chain them together by soldering individual wires to the correct terminal on the LED star. For those not experienced with soldering electronic components this can be an intimidating task, not to mention that excessive heat applied to the LED terminal for too long can destroy the LED.  The wiring forms a chain with the positive terminal on the first LED going to the LED Driver’s positive connection and the Negative terminal on the last LED leading to the Negative connection on the Driver.

RapidLED PNP Wiring

Contrast that to the RapidLED PnP system. A jumper wire connects to the positive and negative connections on the Driver which plugs directly into a terminal board to which up to 7 PnP LEDs can be connected. These terminal boards can also be connected by a jumper wire that plugs into the end of each board to create a string of LEDs as long as needed. any unused terminals on the board are terminated with a termination plug that completes the chain. RapidLED sells a range of jumper wires and extensions to accommodate most any layout. Now there is no confusion about which wire connects to which terminal and the end result is a much neater wiring layout. Replacing a damaged LED or changing the color of a particular LED is now as simple as unplugging it from the board and replacing it with the new product.

When building my first fixture the traditional way it took me a couple hours to solder together all the connections. Using this method I was done in less than five minutes. In my opinion this system has opened the building of DIY LED fixtures to many hobbyists who wouldn’t attempt building a fixture otherwise. Now back to the build.

LED Installation

The final step of wiring up the components involved drilling a small hole through the heat-sink for the Jumper wire that connects the LED Terminal boards to the Driver. I drilled a small hole through the heat-sink to pass this wire to the LED side to make the connection. In this picture you can see the housing that holds the driver and other components and the fan all mounted directly to the heat sink. Now it is time to start connecting the LEDs. For this fixture I selected a combination of 6 Cree Cool White XP-G and 6 Cree XP-E Royal Blue LEDs as these were the only PnP LEDs available at the time. Now they have added XP-E Blue and XT-E to the line up of blue LEDs and XP-G Neutral White. For the added spectrum these new PnP LEDs offer I would incorporate a 25% Blue, Royal Blue, Cool White, Neutral White mix of LEDs. I have been happy with the 50/50 mix of blue and whites in my fixtures especially when a separate circuit for blue and white can be used.

There are several ways to connect a LED to the heat-sink. One method is drill and tap the heat-sink then apply” Thermal Grease” to the back of the LED star and physically screw it to the heat-sink. Another method is to use a thermal epoxy and either screw or apply pressure until the epoxy sets to permanently bond the LED to the heat-sink. I used the third method which I find quick and very effective. It involves the use of a Berquist Thermal pad to connect the LEDs to the heat sink. The Berquist Thermal Pad is made of a heat conductive material with an adhesive coating on each side. The installation process is simple. Just peel the backing off the pad and apply it to the back side of the LED Star, then peel the backing off the other side of the pad and apply it to the heat-sink and you’re done. You can buy the Berquist thermal pads directly form RapidLED however if you have access to a source for the thermal material these pads are made from you can cut pads yourself. They’re not as pretty but do the same job. That’s what I did for this fixture.

Using the RapidLED PnP system the LED installation went like this. Fist connect the standoffs to the Terminal boards. Second connect the terminal boards together with the jumper wire. Now position the terminal boards where they should go on the heat-sink and make a mark where the standoffs touch the heat-sink. Next peel off the backing form the two sided tape on the standoffs and press the terminal boards into position. Once this is done connect the jumper wire from the Driver to one end of the terminal boards and plug in the PnP LEDs. Mark their location on the heat-sink and apply the Berquist Thermal Pads then position the LEDs on the heat-sink.

The final step once everything has been installed and tested is to set the Maximum Current that can be delivered to your LEDs when at full power. Since the Mean Well Driver can deliver up to 1.5A which exceeds the rating of the blue LEDs I used, to protect the fixture from burning out the LEDs you have to open the Driver and adjust the current using the set screw SVR2. Once you have opened the driver and located SVR2 you need to use a multi-meter to measure the amperage through the circuit. The easiest way to do this is to remove one of the LEDs from the circuit by unplugging it from the terminal board and plug in a  Driver Jumper cable (Order an extra cable for this from RapidLED) and connect the leads from your multi-meter to the leads on the jumper cable. Now set your multi-meter to measure DC Amps and energize the circuit. Now turn down the set screw SVR2 until the current you need is reached (in this case 1A. Full instructions for setting SVR2 are available at http://www.vinnymarini.com/pictures/rapid_docs/Using%20Your%20Dimmable%20Driver.pdf  (Note: The picture at the left shows how to check the amperage using standard wiring. The process is the same using the jumper cable with the PnP system as described above.)

The remainder of the project consisted of cutting a splash shield to protect the LEDs and building the component cover. The Black Anodized heat-sinks form RapidLED have a channel built into the bottom of the heat-sink for the splash shield.  I was able to bend a piece of acrylic to make a very clean cover for this fixture that will look great over any small tank. All in all I am very happy about the way this fixture came together and like every project it has given me some ideas for my next build.

Related posts:

1. RapidLED PnP System at the February Meeting
2. January Meeting Canceled
3. Terence’s DIY LED Build – Beta36 x 2
4. DIY LED Light for your small tank for <$200
5. Insane DIY Aquarium LED Build