Tall grass or thick bush? No worries!

Hi,

My name is Vaidotas. I have been flying few years  now. I like planes but I fly fpv quads more often these days and  sometimes I crash. What happens in hard crash? Usualy battery ejects and  you have to walk in zig zags in tall grass in order to find it. I lost  one quadcopter in huge field :( R.I.P. But no more! said I one day.  Battery ejects because of kinnetic energy. I can not control speed but I  can controll battery weight, so I decided to have separate small one  cell inside. I used 3 methods to give me buzz when battery ejects:

1.  Always feed flight controller with power from 1s battery and use buzzer  in case of crash. But 4.2V is ususaly is not enougth so we also needs  step up controller to boost it to 5v. Since this battery should never  eject it should be fasten safely to frame. It is very hard to charge  such battery and you never know when it will discharge durring flight.  So.. I have put one more component - P4096. this is small one cell  charger that will always charge one cell from main battery so quadcopter  will use internal battery only when main ejects. Sounds simple? Simple  it is! See schematic below:

1S battery connects to P4096 and P4096 to UBEC. UBEC will charge the battery if needed.

1S  battery also connects to booster board that will always give 5v to  flight controller. Just battery would be enougth to power FC and you  dont actualy need charging components but you will need bigger battery  for longer flight sessions  and you have to charge it every time.

Remember to waterproof everything since quadcopter can(and will) land in wet grass.

This  method is great if you use more than FC like GPS, VTX, telemetry, but  it is quite heavy and takes some room in your quadcopter.

2) If  you don't need to feed FC and you just want some alarm when battery  ejects you can use arduino mini. 4.2V is enougth for it to work long  time. Schematic is very simple, all you need is some switch to power up  arduino mini,small battery and a buzzer.

Upload arduino code:

void setup() {
pinMode(4, OUTPUT);
}

void loop() {
int sensorValue = analogRead(A2);
if (sensorValue<100){
pep(); pep(); pep(); delay(100);
peep(); peep(); peep();      delay(100);
pep(); pep(); pep();  delay(100);
delay(1000);                
}
}

void pep(){
digitalWrite(4, HIGH);  
delay(100);
digitalWrite(4, LOW);  
delay(100);
}

void peep(){
digitalWrite(4, HIGH);  
delay(300);
digitalWrite(4, LOW);  
delay(100);
}

3)  Another posibuility is having negative gate (74HC04). This is probably  cheapest option (bought 5 gates for 1.5GBP). Once FC loses power gate  will be open and buzzer will start to buzz. Simple but works very well.  You can use smallest battery you can find. Its qutie light as well -  mine was around 8g.

If  you like in fly unusual places, do some epic freestyling in the  mountains you must have some means of finding your crashed drone. Have  fun!