Tear down of hand induction mini R/C helicopter
I just found a very small broken helicopter that is very cheap at present. Since it is with a broken rotor blade, it finds very difficult to repair. It has micro level parts so I decided to show you how those parts working.
The picture shows an upper blades broken Mini R/C Helicopter. This is with Coaxial type configuration which having two main rotors stacked on top of each other and no tail rotor while each main rotors are spinning in opposite directions with equal speed to keep the helicopter at a stable position on air when flying.
Engine and control Circuits
Engine and the control circuit of the helicopter are equipped with a small motor, gear wheels rotating opposite direction, 3.7V 90mAh Li-Po battery and the circuit. The circuit is equipped with micro controller(MC), infrared emitting LED and infrared absorbent sensor,on off switch, charging port and other electronic parts.
Engine Mechanism gear box
The following picture shows how the opposite rotating wheels are powered from the motor.
Circuit Board
The control circuit seems simple and very small in size. But the inside is very complicated with a micro controller(MC). Here, the 8 pin main IC is a MC chip (Unmarked) which is difficult to find data sheet. But I explain you how it is working. When power up the helicopter, it will spin after a 3 seconds delay. The micro controller will power up the motor through the N Chanel MOS FET by Pulse width modulation with the above delay. After that it will increase the rotating speed of the motor and will fly. Then after few seconds it will gradually decrease the speed of the motor and the MC is waiting for the feedback signal coming from IR sensor. If your hand or any other object kept under the helicopter the MC will command to the motor to increase its speed. Then its flying height will be getting increased. Above process will be repeated until sending the stop command by the remoter controller.
Circuit Board Parts Identifying
TL1838 IR Receiver
One of the major electronic components of this circuit is the IR receiver. It can pick up 38Khz burst frequency coming from a stranded IR transmitter about 70 degree angle and nearly 15m distance. Working voltage range is 2.7-5.5V and draw current will be about 1.5mA.
LTC4054 or XC6801 Li-Po Charger IC
Now a days it is very famous the surface mount single chips, single cell battery charging IC and the same are used in this application as well. These types of IC's are widely used in charging IC and many hand held devices. The operating voltage is 4.25-6.5V and maximum charging current is around 500mA. The most convenient application of this is the USB port enabling it to draw current on charging. This type of USB charging is popular today.
IR Remote Controller
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