Lauren loves confetti.

Several months ago, Lauren asked me if there were a way for us to drop confetti under the tent at our wedding reception. Confetti machines for weddings were really expensive to buy (read: around $6000), but she imagined I could build something where the confetti would be trapped like balloons under a net and gently be released upon the unsuspecting wedding guests.

Gently? I had other ideas. Over on the Make Blog, one of the How-To Tuesdays was this compressed air rocket launcher. Perfect. I was confident that I could turn it into our confetti launcher!

After a three hour adventure at Home Depot, some internet shopping at SparkFun, an evening of soldering, and an afternoon of gluing PVC together, I was ready for a small indoor test in our apartment. I shredded some newspaper as a substitute for the confetti and used our bicycle pump to “charge” it to about 20psi.

3-2-1. A push of the red button and poof! It rained “confetti.” And of course, there is video proof.

After two grueling months, the wait was finally over. A large, but light, package had arrived in the mail taped shut at one end with Atlantahobby.com packaging tape. Lauren had ordered it for me months ago for our engagement anniversary, but every hobby shop locally and online had it back ordered until the middle of February. It took time for it to travel overseas from Germany.

This weekend it made it here. It took great restraint, but I waited until the next day to open the package. I wanted to make sure I had enough daylight to photo document it, and that is what I did.

I swiftly used my Swiss Army knife to dispose of the packaging. Its contents were what I had been waiting for all this time; my very own Multiplex EasyStar R/C airplane. This is the same aircraft used by the developers of the ArduPilot and our platform for the Flying Android project.

The EasyStar is an ideal platform for learning how to fly R/C airplanes, plus it is actively used for aerial robotics. I plan to pursue both as soon as we leave the unfriendly winter weather behind.

The Multiplex EasyStar comes as a Ready-to-Fly (RTF) kit, so there was little for me to build once I had it unpacked. The Hitec 72Mhz 4-channel single stick transmitter needed eight AA batteries. Replacing the batteries required taking apart the entire transmitter; therefore, rechargeable NiCd batteries should be a wise investment.

Inside of the fuselage is the Hitec 72Mhz 6-channel receiver. Only three of the channels are used on the transmitter and receiver: one for the throttle, one for the elevator, and one for the rudder. This leaves the fourth channel open for customization, which we use for toggling the autopilot on/off on our Flying Android EasyStar. Next to the receiver is the electronic speed controller (ESC) and a NiCd battery pack can be found in the nose of the airplane.

The assembly required to put this airplane together merely took ten minutes. The elevator is glued to the tail and attached to one servo, while the rudder is glued on top of the elevator and attached to the other servo. The wings are joined by a plastic rod and can be easily attached and detached from the aircraft.

I was ready to test the servos and throttle in no time. First, I turned on the transmitter and then the receiver (and vice versa when powering off), else I could risk damaging the servos or other electronics. Then, I verified that the trims and stick moved the control surfaces in the correct directions. Finally, the throttle needed to be tested, so I ramped it up to full power!

I have already started to make a list of modifications in my head: switching over to the 2.4Ghz transmitter from the Blade CX2 helicopter, a brushless DC motor and ESC for more power, and a LiPo battery pack for longer flights. Plus, a camera module is definitely a must.

Make sure to check out my Flickr set for more photos.

A few years ago, my dad entrusted me with his E-Flite Blade CX2 R/C coaxial helicopter, because I became interested in making it fly autonomously. I had a free project in one of my CS courses and decided to build a stabilizing auto pilot for the helicopter around an Arduino Mini, but more on that in a later post.

The helicopter is fairly easy to control indoors, as soon as I figured out to stay way from the ground, the ceiling, or any furniture. Flying too close to any such obstacles creates turbulence and backwash, which make the helicopter difficult to control. This also makes it almost impossible to fly outdoors, even in low wind conditions. The helicopter is powerful enough to lift itself off the ground, but can carry only a small payload of extra electronics. However, it is a lot of fun to fly!

Since the helicopter belongs to my dad, I made sure to take good care of it, but small crashes are inevitable in test flights around the living room in a studio apartment. The worst crash that could happen is a power-on blade strike, where the blades strike an object while the throttle is not at 0%. Either the blades could shatter on impact, or worse the blades are stuck, which cause the DC motors to over-current the 4-in-1 control unit. As Murphy’s law dictates, just that happened to me.

The short in the control unit from the over-current remained well hidden, since there was neither a spark nor a small puff of smoke: the #1 sign for any electronics geek that something just broke. I didn’t know something went awfully wrong until the next time I tried to fly the helicopter.

Plug the battery pack into the control unit. Go. Turn on the transmitter. Go. But the transmitter wouldn’t associate with the receiver in the control unit, which simply blinked red and green. Ok, let’s try it again. Unplug everything. Plug the battery pack in and turn on the transmitter. Same red and green blinking. Oh, no. Panic. Let me read the manual. Rebinding? I tried to rebind the transmitter and receiver with the bind plug, but that didn’t fix it either!

I spent the afternoon frantically searching the Internet for a solution, until I came across a discussion about Blade CX2s and the ‘over-current’ problem. I soon learned that the control unit was lost and this could have been easily prevented with a fuse between the 4-in-1 control unit and the DC motors. A $5 fuse? Why wasn’t this included with the helicopter in the first place? Needless to say, I was a bit furious that I had to replace the $60 control unit.

So before you have to spend $60 to replace a destroyed 4-in-1 control unit, invest $5 in resettable fuses (EFLH1206 Over-Current Protection/PTC Fuse Harness). These positive temperature coefficient (PTC) devices are non-linear thermistors, which at some specified level of current break the circuit and disconnect the motors from the control unit. The fuses reset once the current drops off on the wire.

The resettable fuses need to be installed between the control unit and each motor (not the servos). Check the photo below to see what it should look like installed on your helicopter. The fuses will add some length to the wiring, but you can easily stow them away in the cockpit above the control unit.

If you’re lucky, you may have bought one of the newer Blade CX2s, which now ship with the fuses already installed. Either way, next time you get unlucky with a power-on blade strike, you won’t blow your fuse over having to replace the $60 control unit.