The post delineates a simple quadcopter circuit or a drone circuit which can be built by a layman and operated using an ordinary RF remote control module. The idea was requested by Mr. Sahaj
Designing the Quadcopter
In this post we learn how to make a quadcopter or a drone quickly and cheaply using very ordinary components. In one of my earlier posts we learned how to make a relatively complex and therefore efficient quadcopter flying machine without using microcontroller, for more info you would want to go through the following posts:
In the present article we try to make the above design much simpler by eliminating the brushless motors and replacing it with brushed motors, and consequently making it possible to get rid of the complex BLDC driver circuit module.
Since the mechanical construction details of the quadcopter was already discussed comprehensively in the earlier post, we will only deal with the circuit design section and learn how it may be built for flying the proposed simplest drone circuit.
As mentioned earlier this simple quadcopter requires only the basic RF remote control modules as shown in the below example image:
You will need to buy these RF modules from any online store or from your local electronic spare dealer:
Apart from the above mentioned RF remotes modules 4 permanent magnet brushed motors will be also required which actually forms the heart of the drone machine. It could be as specified in the following image with the given descriptions, or any other similar as per the required user specifications:
Electrical Specifications of the Motor:
12V = operating voltage 200mA = operating current 10,000 RPM
How to Configure the Remote Control Receiver with the Motors
Before understanding how to configure the remote control receiver with the quadcopter motors, it would be important to learn how the motor speeds are supposed to be adjusted or aligned for generating the required left, right, forward, backward motions.
Primarily there are two ways a quadcopter can be enabled to move, which are in the "+" and the "x"modes. In our design we employ the basic "+" mode of motion for our drone, as indicated in the following diagram:
Referring to the above diagram we realize that we simply need to appropriately increase the speeds of the relevant motors for executing the desired directional maneuvers on the drone.
This increase of speeds can be enforced by configuring the remote control relays as per the following wiring diagram. In the diagram below we can see an IC 555 PWM circuit wired with the 4 relays of the remote control receiver module of the 6 relays (1 relay being unused and could be simply removed to educe space and weight).
Adjusting the PWM
As may be witnessed in the diagram, the PWM feed is connected with all the N/C contacts of the relays, which implies that normally the quadcopter would be hovering through this uniform and equal PWM feed, whose duty cycle may be initially adjusted such that the quadcopter is able to attain a correct specified amount of thrust, and altitude.
This may be experimented by appropriately adjusting the shown PWM pot.
How to Configure the Relay Contacts
The N/O contacts of the relays can be seen wired directly with the positive supply, so whenever a relevant button is pressed on the remote transmitter handset, the corresponding relay is activated in the receiver module, which in turn enables the relevant motor to get the full 12V supply from the battery.
The above operation allows the activated motor to gain motor more speed than the rest of the motors which consequently allows the quadcopter to move towards the stipulated direction.As soon as the remote button is released, the drone stops instantly and continues to hover in the constant mode.
Identically, other directional motions can be simply achieved by pressing the other assigned buttons, on the remote handset.
The topmost relay is for ensuring a safe landing of the machine, this is done by adding a current dropping resistor in series with the N/O contact of the shown relay.
This resistor value must be calculated with some experimentation such that the quadcopter hovers around a couple of feet above the ground whenever this resistor is toggled through the attached relay.
The shown relays are the part of the RF module receiver, whose contacts are initially unconnected (blank by default) and needs to be wired as indicated in the above diagram.
The RF remote receiver is supposed to be installed inside the quadcopter and its relays wired with the relevant motors and battery as per the above shown layout.
How the Drone Moves:
As explained in the above discussion, when a particular remote button is pressed, it actuates the corresponding relay of the quadcopter module causing the relevant motor to move faster.
This operation in turn forces the machine to move in the direction opposite to the motor which is being switched to rotate at the faster RPM.
Thus for example, increasing the speed of the south motor causes the machine to move towards north, increasing the north motor causes it to move south, similarly increasing east motor speed causes it to move west and vice versa.
Interestingly, increasing the south/east motors enables the quadcopter to move towards the opposite north/west that is in the diagonal mode....and so on.
Pros and Cons of the above explained Simple Qaudcopter remote control circuit.
- Cheap, and easy to build even by a relatively new hobbyist.
- Does not require complex joystick operations.
- Can be controlled using a single 6 channel remote control module
- Less efficient in terms of battery back up due to the involvement of brushed motors
- Directional speed is constant and cannot be varied through the remote control handset
- Maneuvering may not be smooth rather a bit jerky while switching the buttons.