I’m planning an LED floodlight project that will use a lot of square 4-pin LEDs, aka SuperFlux or “Piranha” LEDs. I hadn’t had a chance to use these type of LEDs until now, so after receiving my order this week I immediately went to work on trying them out. This won’t be a very technical review, just a quick look at the specs and my experience with testing the LEDs and what I thought of them.
The LEDs I purchased for the project came from Lighthouse LEDs. I chose them based on the fact that they’re in the United States, and their Ebay feedback is excellent. Prices are good too. I ordered through their website, and the LEDs I purchased were $0.22/each. For comparison purposes, I also purchased some superflux LEDs from my local Radio Shack. They were $2.99/each, which is high, but expected when buying in quantities of one from a retail business.
Here’s the specs for the LEDs:
|Color||Part No.||Wavelength||Angle||Fwd Voltage||Current (ma)||Intensity (mcd)|
|Color||Part No.||Wavelength||Angle||Fwd Voltage||Current (ma)||Intensity (mlm)|
Note: Radio Shack does not use millicandelas for intensity measurement, making it difficult to make comparisons with other LED specifications.
Testing the LEDs
Assembling the breadboard
For the test, I mounted the LEDs on a breadboard with a 5v regulated power supply. Piranha LEDs don’t line up with breadboard spacing, but they can be installed at an angle as seen in the photo.
Note that the Lighthouse red LED (top left LED) appears to be installed backwards, as the chamfered side (which should be be cathode) is connected to the positive voltage rail. I tested several of the red LEDs, and they all have the polarity reversed. I contacted Lighthouse and heard back from them fairly quickly, thanking me for letting them know and indicating they would look into it. It’s not a big deal, as they’re still usable, but if I hadn’t known this before soldering them in place on a PCB board, I wouldn’t have been very happy. The lesson here is that when buying inexpensive “generic” LEDs, it’s a good idea to test them before installing them – you don’t always know what you’re getting. This wouldn’t be likely to happen with name brand LEDs, but I would have paid a lot more than $0.22/each for Lumileds or other brand-name superflux LEDs, and my application isn’t critical enough to justify the extra cost of high-end components. For this project, it’s worth it to me to save a little money at the expense of having to do some additional testing.
Choosing the resistors
The blue/green LEDs need about 20ma of current. The red LEDs are lower intensity and voltage, so I give them a little more current to compensate. The values are approximate as I didn’t have the resistor values needed to get the exact currents I wanted. My final project will run off 12v, so the resistor values will be different for it anyways. The goal here is to get an approximate idea of how they’ll work at the currents I’ll be using in my floodlight project. Here’s the values I used:
|LED(s)||Resistor Value||Approx. Current||Notes|
|Lighthouse Red||100Ω||31ma||I measured it at ~29ma|
|Radio Shack Red||82Ω||29ma|
|Radio Shack Blue/Green||68Ω||22ma||Need 75Ω for 20ma, didn’t have any|
I use the lowest specified forward voltage to calculate the current, so for example the Lighthouse red LED was calculated as (5-1.9) / 100 = 0.031. I did my best to keep the provided current the same between the two brands with the resistors I had available. This isn’t meant to be a detailed comparison anyways, especially since I’m only testing one of each brand/color. Your mileage may vary depending on how you use them.
Brightness on both brands/types of LEDs is impressive. The photo doesn’t do a great job of showing it, but you can make out some differences. The Lighthouse LEDs direct more light forward, which makes sense as they have a narrower viewing angle. The Radio Shack LEDs spread the light out more. The light falling from them onto the breadboard is noticeably more intense than with the domed LEDs. I suspect the domed vs. flat top is part of the difference, but a quick Google search didn’t bring anything up regarding the difference or what the benefits/disadvantages are of each style.
I’m looking forward to using them in the floodlight project. I’ll be using a couple of Big Clive’s PCB Boards and RGB Controller to build it, and there will be 108 LEDs total. It should really light up a room when it’s done!