Hi, Im experimenting with building a mini quad from scratch.

Ive built a 450 size quad before using brushless motors and a CC3D FC and its been performing well but honestly there was no build satisfaction as it just involved assembly of all components.

So this project where i want to build everything from scratch.

This mini quad has 716 coreless motors, a Motor driver board using A2SHB si2302 N-channel Mosfets, 10k Resistors and 1N4007 Diodes.

The Motor driver circuit Description..

(Please see attached Image file)

Gate is connected to PWM signal output ( Turnigy receiver)
Source is connected to ground
10k resistor between gate and ground ( between the gate and source pins on si2302)
Drain is connected to motor(-ve) with Diode in parallel

The PWM signal is provided by the Turnigy 5ch Tx-Rx. The arduino Mpu6050 interface is omitted as i want to test the motor driver circuit.

There are some issues with the build as shown in the video.



As soon as i turn on the transmitter, all the motors start to spin slowly. If i toggle any joysticks to change the pwm signals to any motors, that respective motor spins just a little faster or slower but the motors dont generate any thrust.

However if i bypass the Mosfet and connect a jumper between the Drain and Source, the motor spin velocity is high enough to lift that arm of the quad of the ground.

I have my doubts on the following..

1. The choice of Mosfet. Im beginning to wonder if si2302ds is good enough but 90% of all reference i look up have used this mosfet.
2. The 10k resistor, is it overkill?

Can someone please help with a solution. Would be obliged..

Thank you.

They are absolutely working fine. The pwm duty cycle of receiver output is 10% (mostly) to be the maximum. So if they are connected to gate os mosfet then it would not be able to increase its speed. That is why you need some conversion mechanism such as ESC or flight controller. Both of them convert and mix the pwm. Moreover in quadcopter the mixing of input is also done.
You need to go through quadcopter flight controller guides also.

Thx so much for the reply Bala,

Ive been breaking my head about what could be wrong. However ive also tested the motor using a pwm tester thats available in the market and it showed me the same results..

U mean to say that if i route the pwm via my arduino, then it would drive the motors as expected?

Thanks so much

Servo tester is just an emulator of receiver but you don't need a radio.
If you are passionate about building a flight controller then just go through this thread.
http://www.rcindia.org/chatter-zone/potocol-designing/

Hello,
How are you going to drive the motors? Using PWM from the arduino? In that case it should be fine, but remember to use the pwm values 0 for minimum and 255 for maximum (for a 8bit PWM). RC signals are also PWM pulses, but their duty cycle varies from 1mS to 2mS where the time period of a single PWM pulse is almost 20mS. The motors will turn with full speed only if you drive them with PWM having 100% duty cycle, i.e. 20mS. An arduino can do that with ease, but output from a RC receiver isn't adequate for that.

Thanks so much Bala and Dipanjan for your replies and much needed advice.

I will get to it right away and keep u updated on the progress.

Much obliged by the help...