Before beginning the actual process of attaching LEDs to the Rotor Bits tricopter and wiring them up to work, I just want to take a moment to cover a bit background information so the process will make the most sense.
The LEDs we will be using on the tricopter are strips of six LEDs available from HobbyKing. We are going to use two different colors. This will allow us to put two strips of one color on the front two arms, and a third strip in a different color on the rear arm. This way, when flying, especially when flying at dusk, it will be easier for us to tell which side of the tricopter is front. So, for example, in this Instructable, I am using two blue LED strips on the front arms and a green LED strip on the rear arm. You can choose any color you want though, many different colors are available:
The LED strips run off 12V, which, as it happens, is the power supplied by the battery. So, we could just connect the LEDs straight to the battery, but the question is, should they be wired in series or parallel?
The answer is, we want to wire the LED strips in parallel. Here’s why:
Our battery supplies 12V and, as far as LEDs are concerned, unlimited current (part of the reason we use LiPo batteries for multirotors is because they can discharge a very high current, far higher than we would need for any number of LEDs we could cram on our tricopter). If we were to wire the LED strips in series, that 12V would be distributed among the three LED strips. So, each LED strip would get 4V, not enough to run the LEDs.
With the LEDs wired in parallel, however, each LED strip gets 12V. In parallel, the current required for the system is sum of the current required by each LED strip. But, as I just mentioned, current is no issue for our battery. The 12V for each strip is enough to make them nice and bright. So, we will be wiring the LED strips in parallel, with all the negative leads wired together and all the positive leads wired together.
If you want some more information about wiring LEDs, there is a nice, simple tutorial at http://www.quickar.com/ledbasics.htm.
There is, however, one more issue to address here. I think it is nice to be able to turn the LEDs on and off. If you are flying in the daylight, you might wish to turn off your LEDs, or maybe you just don’t want them on all the time. We will be adding a switch to the LED circuit. The nice thing is that the switch we will use is turned on and off by the receiver, so we can turn on and off the LEDs remotely with the radio transmitter. Specifically, we will use the CH6 toggle switch to control the LEDs.
Let’s get to the build.
Create Wiring Harnesses
The first thing we need to do is make ourselves some wiring harnesses to connect the jumper pins on the LED strips to the bullet connectors on the battery. You will need two wiring harnesses: the first goes from three jumper pins to a male bullet connector, and the second goes from three jumper pins to a female bullet connector.
So take two red male-to-male jumper wires and two black male-to-male jumper wires and cut each in half. Strip the ends of all the wires by about ½ inch. Take the three red wires and twist the ends together. Then, loosely double the twisted ends. Repeat this twisting procedure for the three black wires.
Then, break out your soldering iron, and, using the same procedure as you used to solder bullet connectors to the UBEC (check https://www.youtube.com/watch?v=B9yY9Kk4bEA for a quick tutorial) solder a female bullet connector to the black wires and a male bullet connector to the red wires.
Solder Bullet Connectors to the Receiver-Controlled Switch
We will also need to solder bullet connectors to the leads of the receiver-controlled switch since the switch comes with these leads unterminated. Use the same procedure we used when soldering bullet connectors to the UBEC.
Attach the LEDs to the Tricopter
Alright, it is finally time to attach the LEDs to the tricopter frame and connect them electrically to the rest of the system. As before, we will do all the wiring and verify that everything functions as expected, before actually attaching everything to the frame.
Now that we have the whole LED system wired, we will test the LEDs just to make sure everything is working before we start zip-tieing everything to the frame (it will be annoying to undo this if we find the LEDs don’t work after we do it). Connect the battery to the wiring harness and turn on the radio transmitter. Then, if the LED’s have not turned on already, which would happen if your CH6 switch happens to be on already, flip the switch. You should be able to turn the LEDs on and off. The LEDs should also be quite bright, we want to see them clearly from far away after all.
Fasten Everything to the Frame
The last thing to do is attach everything to the tricopter frame. As we've done with all the rest of the tricopter components, I like to use zip-ties for this task. There is a very important piece of information to keep in mind while you are mounting your LED strips. Carbon fiber is electrically conductive, its kinda like pencil lead which you might have used in grade school science class. The carbon fiber tubes we used to build the tricopter have a coating that is supposed to prevent the tubes from conducting electrical current, but the coating is very thin. The little metal spikes on the bottom of the LED strips, the leads from the LEDs themselves, are more than capable of penetrating this layer. This situation will result in an electrical short, which will damage your tricopter. I actually learned this the hard way and an electrical short fried one of my LED strips (specifically it fried the resistors). Also it smells really bad. Anyway, to avoid this issue, put a few layers of electrical tape onto the tricopter arms. This will make a nice nonconductive mounting pad for the LED strips.
Then, after mounting the LED strips to the tricopter frame using zip-ties on top of the electrical tape pads, mount the receiver-controlled switch to the Rotor Bits tricopter hub. Finally, fasten down all the wires so you don’t end up with loose wiring finding its way into the propellers.
And you are done! By this point your tricopter probably looks really crazy, like some kind of mad scientist contraption with wires and LEDs everywhere. I actually think it looks pretty cool, especially with the LEDs. Enjoy your much more glowing tricopter!