Yes, you read the title correctly. Don't worry, no cats were harmed in the making of this project. Cats are fun in their own right, but this is 2014! Isn't it about time we brought cats into the modern era? And by bring into the modern era, I mean combine with lasers. In this Instructable I'll show you how to turn an off-the-shelf RC toy and a laser pointer into a wacky way to accessorize your feline friend for hours of fun.

Step 1: Parts and Supplies

RC helicopter (RadioShack #: 60-958)

laser pointer (RadioShack #: 63-1064)

micro servo (RadioShack #: 273-765)

NPN Transistor (RadioShack #: 276-2016)

1 K ohm Resistor (RadioShack #: 271-1321)

AAA battery holder (RadioShack #: 270-398)

(2x) AAA battery (RadioShack #: 23-2214)

(6x) AA battery (RadioShack #: 23-2212)

cat harness

thread

live cat

Step 2: Modifying the RC Toy

First we'll need to take apart the helicopter to get the electronics . We wont be using the built in motors, but we will be using the IR receiver and main circuit to control our servo and the laser light.

Once we disassemble the helicopter, it won't be readily repairable, so take a few moments to fly it around and crash it to your heart's content. We don't need the propellers anyhow.

The toy helicopter is held together with a ton of tiny little screws. We'll need to remove all of them to get to the heart of the toy inside. Using a small phillips head screw driver, go to town on the toy and remove any visible screws and pull apart the now loosened plastic bits. Feel free to hack away at the little helicopter since we don't need any of the components except for the main PCB. Out of curiosity I decided to try to disassemble it as much as possible without resorting to cutting or breaking anything. Amazingly, most of the toy is held together without any glue or tiny heat welds, which is quite impressive! Safely remove the PCB once it is free from the body and snip the wires to the motors, light, and battery. Feel free to use them to make the world's smallest personal fan, or perhaps upgrade a paper airplane to a powered version.

Step 3: Modifying the Micro Servo

First, peel off the stickers along the servo case.

Using a small screwdriver, remove the tiny screws at the base.

Pull out the driver board. Clip the two wires leading to the motor off and set the driver board aside.

Cut a length of the original servo wires and strip the ends.

Solder the new wires to the motor so it will extend outside of the case.

Replace the base of the servo and tighten the screws.

Having printed the micro servo mount, threat the wires through the hole near the base.(The .STL file is attached)

Press the micro servo firmly down into the mount.

We'll be driving the servo motor with the rc toy's electronics, so we wont be needing the servo control board.

Micro Servo Mount.stl
Download View in 3D

Step 4: Modify Laser Pointer

The full laser pointer is far to bulky to mount to our wee servo, so we'll need to remove the diode and driver from the body tube.The diode module is held firmly in place by friction at the tip, so we'll need to pull it out. I ended up using a vise and pliers to pull the pointer apart.

Once the diode is free, clip off the the spring attached at the end. The spring metal is quite hard, so use some heftier snips to clip it off. I nearly ruined my regular flush cutters, so be warned!

Solder two lengths of wire to the module. Looking at the top of the board, the anode is located at the middle contact of the diode and the cathode should attach where the spring is soldered to the board.

Solder to both ends of the the button with a tiny length of wire. This way the module is permanently "on" when powered by the RC electronics.

Step 5: Solder Electronics

Time for the real modifications! The original battery that powered the heli was rechargeable, but quite small. In addition, the laser driver runs off of ~3 volts. The original LiPo would give 4.2 volts down to 2.7 volts, which could potentially damage the driver. The servomotor originally required 4.5 to 6 volts, but the bare motor will run at much lower voltages, so it will be ok. With all of this in mind, we can safely assume a nice 3 volt average will run everything quite nicely. With two AAA batteries, we'll get the power we need and an increased run time to boot. Just be sure to use regular non-rechargeable batteries (rechargeable batteries wont give us enough voltage, and we still wouldn't be able to use the built in charging circuit)!

Solder the connections for the battery pack to the B+ and B- pads on the main PCB.

Solder the anode (red) wire from the laser to the B+ pin.

Solder the cathode (black) wire from the laser to the collector of the transistor (the leftmost pin when looking at the flat side).

Solder the 1K resistor from the L+ pad to the base of the transistor (the middle pin).

Solder the emitter pin of the transistor (the rightmost pin when looking at the flat side) to the L- pad.

Solder the motor wires to the M+ and M- pads respectively. The polarity doesn't matter for this connection, since we can just flip the servo horn to match the movement we want.

Step 6: Mounting the Electronics

I created three separate mounts for the electronics to make everything easily and firmly sewn to the harness. I designed the parts in Autodesk Fusion 360 and printed them out of PLA on an Afinia 3D Printer. Download the attached .stl files and print them out. The battery pack should snap into place, but the RC PCB will require a dab of glue to remain secure in it's mount.

Step 7: Prepare Cat

Depending on your patience level, this step can either take two minutes or two weeks. The instructions that came with the harness strongly suggest familiarizing your cat with wearing the harness for a couple weeks. This includes keeping the harness where your cat tends to sleep, in addition to taking the cat out for walks with it on. I opted to skip this step, but it should aid in your cat's attitude towards wearing it!

Attach the assembled unit to your cat. (Your cat may enter into a trance-like state of awe upon being upgraded. This is normal)