# Comments: PicoBuck Hookup Guide v12

Pages

#### Looking for answers to technical questions?

We welcome your comments and suggestions below. However, if you are looking for solutions to technical questions please see our Technical Assistance page.

• SteveEB / about 3 years ago / 1

One way to walk through the color wheel using flexible intensity levels is to use a maximum intensity parameter and an intensity factor array.

Step 1: Set up channels for each color. const int redChannel = 1; const int greenChannel = 2; const int blueChannel = 3;

Step 2: Establish the intensity factor array to help walk through the wheel. Each color will start from a different index of the array. const float wheel_intensity_factor[12] = {0, 0, 0, 0, 0, 0.5, 1.0, 1.0, 1.0, 1.0, 1.0, 0.5};

Step 3: Establish starting points for the colors using an array index for each color. Here we start with pure red. We will wrap these back to zero as we move through the colors of the wheel one color at a time. int redIndex = 8; int greenIndex = 0; int blueIndex = 4;

Step 4: Set the maximum intensity for each color. Some colors like red tend to be stronger for the same intensity level so we can reduce its maximum intensity. You can play with these colors to get them as close as you can to the wheel colors as you can for your set up. const int redMaxIntensity = 60; const int greenMaxIntensity = 120; const int blueMaxIntensity = 90;

Step 5: Establish a final intensity color that is the product of the maximum intensity multiplied by the array factor, thus allowing us to step through the wheel colors using an 8-bit intensity value. I used this on a DMX512 system that only supported 8-bit intensity values. I started with an intensity of zero in this example. uint8_t redIntensity = 0; uint8_t greenIntensity = 0; uint8_t blueIntensity = 0;

• Member #1603540 / about 4 years ago / 1

OK, so I'm a beginner. Why are each of the 3 input ports on the PicoBuck reading 2VDC when nothing is connected to them? I've disconnected the outputs, so the only thing connected is 12VDC. The VIN does read 12VDC as expected, but each of the 3 input ports read 2VDC even though nothing is connected to them.

The connected LED (Triple Output High Power RGB LED #COM-15200) did come on when I had it connected. But I disconnected it to eliminate any variables while troubleshooting.

• santaimpersonator / about 4 years ago / 1

Hi there, it sounds like you are looking for technical assistance. Please use the link in the banner above, to get started with posting a topic in our forums. Our technical support team will do their best to assist you.

That being said... skimming through the datasheet, I think that information might be illustrated on page 4.

• StolnHeartDealr / about 8 years ago / 1

I was asking myself the same question that Member#606804 had and went on to the Femtobuck's page to see if I could find some answers but no luck there. I'm looking to create a budget LED grow lamp and I want to use the Picobuck to drive some Cree XP-E LEDs. They are ~3v forward voltage and they consume 330mA - 1000mA. I have a 12v 750mA power supply hanging around and with the Picobuck set at 660mA I'd be fine to drive 3 LEDs per channel in series. What I'd like to do though is to try setting the channels up for 1A operation and drive 6 at 500mA each. A pair of 3 LEDs in series, keeping the voltage demand at 12v and splitting the current of 1A down each series of 500mA each.

The AL8805 Datasheet mentions the obvious advantages of using LEDs in series and plots data using LED series examples for simplicity. It does not warn against using LEDs in parallel nor does any of the Sparkfun pages about the product. Use of common Cathode/Anode LEDs would not work because this product doesn't support bridging channels.

I think if you know how they are wired and do the calculations correctly you should be fine. You just need to keep in mind that when you choose to wire something in parallel you're not going to get the full current capability of the channel how you set it up. Thankfully the Picobuck is pretty flexible letting you choose a target current with the sense resistor. One other thing I'd like to mention is that if you do short those pads to enable 660mA operation and later change out the sense resistor keep in mind that there are now two resistors in parallel and you'll need to either un-short the pads, remove the second resistor or swap them both to the appropriate values for your corresponding target current.

• Member #606804 / about 8 years ago / 1

I'd like to verify that the PicoBuck can drive three individual Samsung E072A LED engines. My concern is that the configuration of the engine consists of 4 LED's, wired in an "H" configuration, with two in series, those series parallel, with a common cross-connector. I believe the comment concerning not being able to drive common cathode LED's is to avoid connecting the outputs of the PicoBuck to one another, which is not what I would be doing. It looks like this could do the job, just wanted to make sure.

• SFUptownMaker / about 8 years ago / 1

Oooooh, I don't know for sure about that. I'm trying to imagine how that would be hooked up normally.

I don't like the fact that you've got LEDs in parallel with each other; what happens if one of them has a slightly higher bias voltage than the other? Maybe the H wiring offsets that; I don't know.

How is it normally driven? By a constant current driver?

• dalanmiller / about 8 years ago / 1

I'm looking to build a battery pack that can handle up to 12V, does Sparkfun provide batteries I can put together in a series to do this?

• SFUptownMaker / about 8 years ago / 1

Yes, we do, but charging them is another matter.

We sell quite a few different flavors of Lithium Ion Polymer batteries, and those have a nominal voltage of 3.7V per cell. You can stack 3 of them to get close to your 12V output, but we don't currently sell an easy solution for charging them. We do sell a multi-cell, multi-chemistry charger but you'll have to provide a sufficiently high voltage power supply (>12V, for sure) to run it, and you'll need to look into how the cells should be wired for it (it wants to sample the voltage of each cell individually to make sure they're properly balanced).

If you've found an issue with this tutorial content, please send us your feedback!