RC Helicopter Toy

The electronics of a helicopter rc

The helicopter as well as having the mechanical parts and well constituted by some electronic components.

Among them are the servicomandi, remote controls, receivers, gyroscopes, the speed governor (technically called ESC), and obviously the engine, which can be of brush, brushless or Glow (burst).

but let’s start with order by servicomandi, and which a component that has a very important function, in fact, the servicomandi are related to the mechanics of an rc helicopter, specifically are linked via the adjustable lever to the swashplate.

The Swashplate (Collective Pitch)

The swashplate is a mechanism used by helicopters consisting of two rings with interposed a ball bearing. The upper ring can swing forward / backward and sideways, driven lower ring and is integral with the motor shaft and with the rods that control the variations of the cyclic and collective pitch of the rotor blades.

The lower ring does not rotate and is interlocked by a series of levers relative to the commands of the cyclic and collective pitch variation. A swash plate is also used for the tail rotor but only to the variation of the collective pitch, controlled by a pedal, from a radio control in the case of a radio-controlled helicopter.

  1. fixed outer plate (blue)
  2. rotating inner plate (metal)
  3. Ball joint
  4. control along the yaw axis. Tilts the rotor in the longitudinal direction and prevents rotation of the outer
  5. control along the roll axis. Tilts the rotor side
  6. Connecting rods (colored metal) to the rotor blades

Black connecting rods which vary the pitch of the blades controlled by the internal plate

The Servicomandi

The actuators are the main type of actuator used in the models: transform the control pulse in the angular position proportional to a lever, said bracket, obtaining that the angular position of this is a copy of the angular position of the Tx stick. In Figure 1 you see two servants of different dimension open to show the internal components. Normally you do not need to perform any maintenance other than a possible lubrication of the gear unit if it is a bit hard and noisy. For mechanical servants are still available spare parts; this is well, however, leave it to specialized personnel.

Inside a Servant

In figure 2 it is shown the interior of a servo pattern. The control signal comes from Rx together with power cables and electronics provides to control the motor control, via a sharp reduction gearbox, rotates an outer brackets using a slotted plug (called ribbed). The graft is also connected to a potentiometer which serves to read (by means of a resistor or a voltage) the angle of rotation, in order to check that this corresponds to the desired one, and then the electronics have to stop the motor control in the correct position or control of the movement in one direction or another to reach it.

Analog or Digital? Which One to Choose…

The way you handle engine controls for classifying servants into two categories: analog and digital, whose principles of operation are shown in Figures 3 and 4.

In the case of analog servo control it is generated by a timer, activated by the control pulses, which produces a control pulse of duration proportional to the resistance of the potentiometer; the comparator checks whether they are of equal duration and in the case commands in a direction or in the engine. The command frequency is scanned by the pulse frequency from the radio, also slight differences between command and control will be ignored by the hysteresis of the comparator (dead zone necessary to prevent oscillation). To improve the response digital servos use a microprocessor that transforms into numbers is the command and control shall administer all the time the engine without waiting for the command from the radio. The response speed is increased, the dead zone is almost nothing and the pair is much more constant, in contrast, the absorption (not to use them with BEC circuits or alkaline batteries!) And the inner wear are significantly higher for… not to mention the cost!

So digital servos should be used only where strictly necessary. Other important parameters in choosing a servant are the pair, expressed in Kg / cm (typically 3 kg / cm for the average models and 1.5 kg / cm for small electrical, but there is from 0.6 to 18 kg / cm), and the speed of response expressed in the time required to rotate 60 ° (typically from 0.1 to 0.25 seconds excluding winches, much slower).

Other important selection criteria are the weight and bulk which are of course contingent on the type of model to be managed; usually small electric models require servants with lower pairs but weight and very compact dimensions: often the microserfs are classified in their own grams of weight.

Another selection criterion is the type of gear unit, in which the gears may be nylon, or carbon composite, or aluminum variously treated, or titanium and also the presence of bushings or bearings. Last and not least important criterion is how much you want to spend. In some recent digital servos you can also make working schedules directly with IPD technology. In most models you can increase the speed and torque by feeding to 6V (5-cell) instead of 4.8 V (4-cell).

Gyroscope

The gyroscope is a rotary physical device that, due to the law of conservation of angular momentum, tends to maintain its axis of rotation oriented in a fixed direction. In mathematical terms, a rigid body S is a gyro if the tensor of inertia relative to the center of gravity admits a simple and a double eigenvalue. The eigenvector corresponding to the eigenvalue is simple axis gyro… continued on wikipedia….

As you have so well understood the gyroscope and an indispensable device without gyro you do not have a stable and precise flight and you risk losing the easily helicopter orientation.

Like everything in the market are inexpensive gyroscopes and gyro more expensive, and’ obvious that from an economic and an expensive giscopio the difference is there, but it s also true that I personally flew economic co gyroscopes and with the best gyros which exist on the market and I can say that for a quiet flight without making maneuvers 3d crazy, you can fly well with a cheap gyroscope.