Downed Aircraft Alarm

I developed this downed aircraft alarm after having a "fly away" with one of my drones. This system will function on almost any RC model.

The system runs off of a 9-volt battery and is triggered by a loss of signal (or power) on a ready to fly aircraft, or can be controlled by the auxiliary channel on your remote (signal loss or a manual switch will set off the alarm).

The battery will last for over 150 hours (physical test completed at 21 degrees celsius). Since the power system is separate from the aircraft, the alarm will function during a complete system failure.

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For this instructable you will require:

An Arduino Nano

Two Piezo Alarms

Jumper Wires

Bread Board (All above available http://www.gearbest.com/kits/pp_244840.html)

Prototyping Board (http://www.gearbest.com/development-boards/pp_153862.html)

Scrap Wire

Female Arduino Pins (http://www.gearbest.com/diy-parts-components/pp_23...)

A Soldering Iron and High Tech (super fine) Solder

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The Quadcopter Used in this instructable ins Syma X8W. Available here:

http://www.gearbest.com/rc-quadcopters/pp_193218.html

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Using jumper wires.

Wire the positive pin on one of the Piezo alarm to digital pin 9 and the positive pin of the second Piezo to digital pin 10.

Wire the negative pins of the Piezo's to the ground pins.

Using the code provided above, cycle through the frequencies available to the Piezo.

Monitor the 9600 band of the Arduino serial communication. Note the frequency or pair of frequencies that is most annoying and/or loudest.

This will ensure that the alarm frequency is within your hearing range and is suited to your particular Piezo Alarm.

Place female pins on the prototyping board to connect to:

Voltage input/ main Ground pins (VIN & GND, top right in diagram).

Digital Pins 9 & 10 (for Piezo, center left in diagram)

Digital Pin 11 (for Led Pass-through)

Digital Ground Pin (mid-top left in diagram)

Analog Pin 0 (to detect LED)

Power and ground pins for each Piezo.

Use hot glue to hold the female pins in place.

Step 1: Solder wires between the negative piezo pins to the digital ground

Step 2: Solder wires between digital pins 9 & 10 and the positive pins on the piezo's

Step 3 and 4: Solder wires between the external power input pins and a 9-volt power connector.

Step 5: Solder a wire from Analog Pin 0 to the LED In.

Step 6: Cover the exposed contacts in hot glue to prevent shorting

Step 7: Mark and cut out the prototyping board using a hacksaw or Dremel.

This code tests for voltage on Analog pin 0, if none is detected two piezo alarms will be sounded indefinitely.

To protect the alarm (and ensure that it remains attached to your aircraft in the event of a crash) you will want to securely mount it inside of the fuselage.

On my Syma X8 this involved the removal of a few screws (as shown above).

If your aircraft already as a low voltage/signal loss alarm you will want to tap into this. On my quadcopter the LED's flash whenever the battery reaches 10% or the signal is lost. The setup shown on the X8 passes the led power through the Arduino. If the LED's flash once the Arduino is powered on, the alarm will continue to sound for hours.

Alternatively, if you have an extra channel on your remote you can set up failsafe. Using the same code as above, wire the extra channel to Analog pin 0 on the Arduino. If the extra channel is ever turned off (either manually or due to signal loss/power failure) when the Arduino is on, the alarm will sound for hours. Additionally, I ran power from the quadcopter to the alarm so it can run parasitically off of the quadcopter.

One your drone is powered on and paired with your remote, plug in the battery to the Arduino.

NOTE: If this is done in the reverse order the Arduino alarm will be activated.

Through field "crash" testing I have found that the alarm is audible through approximately 100 meters of dense brush, and even further if the wind is blowing the sound towards you. The alarm can sound continually for over 6 days, much longer than any quadcopter battery would last, and since the power system is separate it will function even during a dreaded LiPo failure.

If you have any questions or suggestions for improvement feel free to comment below or private message me.

Have a great day!