Flying a syma helicopter from your keyboard, WASD style

2013-01-28T02:16:00.001-08:00

Last December, I bought a SYMA S111G helicopter but quickly got bored of it. After I stopped playing with it, my girlfriend decided to give a shot at flying it but crashed it so often that the blades broke within 10 minutes. I thought her flying skills were really poor and decided to make flight control much easier to manage for her. I decided to make a control from a keyboard so that it was easier to fly the helicopter.

Summary of project:
Sending keystroke commands to an arduino, and using a LED set up to send infrared signals to the helicopter, instead of controlling it by the remote that came with it.

Parts you need:
SYMA S111G Helicopter ($25)
Arduino Microcontroller and cable to connect to PC ($30)
Infrared LEDs (Preferably bright ones)
Bipolar Junction Transistors (I used a 2N3904 NPN transistor)

Main idea:
I had to figure out how the remote communicates with the helicopter. After taking apart the remote, I measured the signal that was emitted through the infrared LEDs. The signal turned out to be a 38kHz signal. A quick search online showed that someone has decoded the signal protocol for syma helicopters already. The site is http://www.mikekohn.net/micro/syma_s107_no_fly_zone.php.

Basically, I just have to interpret the keystroke commands to the keyboard, translate it into the remote's protocol (into bits and bytes), and have the arduino make the LED flash at 38kHz to transmit the message to the helicopter.

Having played battlefield 3, counterstrike and other 1st person shooters, I decided to use WASD to control the directions of the helicopter. I used K to increase the throttle speed, L to decrease it, and M to turn the motor on or off suddenly.

For the electronics geeks:
1. The protocol is carried on a 38kHz square wave. Each period is about 26 microseconds, with a duty cycle of 50%.
2. A 0 is transmitted by 0.3ms on, 0.3ms off.
3. A 1 is transmitted by a 0.3ms on, 0.6ms off.
4. Each message consists of a 2ms on, 2ms off header, followed by 4 bytes of data and a 0.36ms on footer.
5. Byte 0 is the yaw data. 00111111 or 63 in decimal is the neutral yaw point. A higher number is to turn left, a lower number is to turn right. The MSB should be transmitted first, LSB last.
6. Byte 1 is the pitch data. 00111111 or 63 in decimal is the neutral pitch point. A lower number is to pitch down (move forward) and a higher number is to pitch up (move backwards). Same as before, MSB transmitted first. Same goes for 7. and 8.
7. Byte 2 is the throttle data. At full battery, a throttle speed of around 200 is hovering and slowly climbing up. You can see how your helicopter works with different battery levels and weights attached.
8. Byte 3 is the trim data. Since my helicopter was working perfectly with 0 trim, I didn't have to try any number for this. You should experiment with yours to see what works best.
9. The time between the start of two messages is 120ms.
10. The schematic is shown here

9V is quite high for the operation of this circuit, but given that pin 12 of the arduino gives 5V when high, I wanted to be on the safe side of having the transistor in forward active mode. If you have trouble and burn out the LED, maybe consider adding a 100 ohm resistor in series with the LED.

If you want to take a look at my code, feel free to contact me and I will get back to you in a few days.

I will add pictures over the next few days.

Note: Somebody has actually created a similar project before me, and I tried to use his code. However, I couldn't understand some segments of how his code flows, so I changed the way the code controlled the helicopter. Other than that, I used the skeleton of his code. You can view his project at http://www.avergottini.com/2011/05/arduino-helicopter-infrared-controller.html

My name is Yong Keong and I am an engineer.

Flying a syma helicopter from your keyboard, WASD style