Drones used to be something of the future. The unmanned aircraft are now available for purchase from a few dozen euros. If you spend a little more, you can even use a drone for great photos or video recordings. In this article we show the different types of drones and tell you what to look out for when buying a drone.

1. What is a drone?

A drone is simply an unmanned aircraft that you can control from a distance. Thanks to several propellers on the top side it is possible to ascend to a height of dozens or even several hundred meters. Originally drones were mainly used by the army to explore unknown territory with video recordings, guarding boundaries or throwing bombs.

Nowadays drones are also increasingly used by companies and consumers. For example, it is possible to inspect high-voltage power lines at high altitudes. Furthermore, drones are interesting for courier companies for the delivery of parcels. Packet service DHL has its own drone to deliver goods to the German Wadden Island. Consumers usually purchase an unmanned aircraft to get out nice stunts or make beautiful photo and video recordings.

2. Number of propellers

Drones are available in all shapes and sizes. You determine in advance what your main goal is. Most drones for his quadcopters. Four propellers drive these devices. Two propellers turn clockwise and two counterclockwise, allowing the drone to take off via upward pressure.

The quadcopter can make various movements by changing the speed of the four engines. When you like to get stunts out, you do not need such an expensive copy. With stunts you can think of loops and flips. From about thirty euros there are already very small quadcopters for sale. Drones with a built-in camera are very interesting. From a great height you can take beautiful pictures of, for example, a nature reserve, beach or more. In addition to models with a built-in camera there are also quadcopters on which you can mount your own camera. Do you want more control? Then a drone with more than four propellers is interesting, like a hexacopter . These drones have no less than six propellers.

3. Control

Most drones can be controlled via a supplied remote control or controller. There are also models that you control via an app with your smartphone or tablet. Quadcopters have a central bearing point and are therefore very stable. This makes it relatively easy to control them. Nevertheless, some exercise is required. Small drones with a wingspan of up to thirty centimeters are usually suitable for both indoors and outdoors. In addition, it is important that there is little wind with compact quadcopters.

The control of most drones works with various channels. Each channel represents a separate direction. The more channels a drone has, the more options there are to choose a direction. A drone with at least four channels is preferred, because you can then go in any direction. A drone with six channels is even capable of flying upside down! The controller of a drone contains two sticks with which you can determine the speed and direction. There are also examples where you can control the drone with your smartphone.

4. Battery

The flight duration is a very important feature of drones. Cheap types are equipped with a small battery so they can only last a few minutes. A drone often describes how long it can fly on a full battery. Take this information with a grain of salt: the flight time depends strongly on the flight behavior. If you continuously perform stunts at maximum speed, the quadcopter battery will probably also drain a little faster. See also how you can charge the drone’s battery. More expensive types provide an adapter, while charging low-cost drones by “hanging” them on a computer via a USB cable. The battery capacity is usually displayed on the controller, so you know how long you can fly.

5. Distance

The range between the controller and the drone determines how high and how far you can fly. Incidentally, there is a restriction in Dutch legislation. Some drones can fly no less than two kilometers, but the maximum permitted height is ‘only’ three hundred meters. In practice, cheap drones usually have a range of a few dozen meters. This is a good height for making stunts. If you want to take camera shots, it may be worthwhile to fly a little higher. You can then photograph a larger surface. For these purposes there are drones with a special controller with more range. This way the Parrot Bebop Drone 2 can be controlled up to two kilometers away.

6. Photos and videos

If you plan to take camera shots, you obviously want the images to be razor sharp. Although there are enough affordable drones between one hundred and two hundred euros including a camera, not everyone is satisfied with the quality of this. So first look around so that you can be sure that you buy one that suits your needs.

For example, the Parrot Bebop Drone 2 has a 14 megapixel camera on board. In addition to the drones with integrated cameras, there are also types on which you can mount a GoPro actioncamera , such as the JY-X5 Drone Quadcopter and Traxxas Aton PLUS . In that case, the manufacturer supplies a special holder to attach to the GoPro camera. Drones on which a camera with a wide-angle lens is mounted have the advantage that you can record or photograph a large area. Nice is that with some drones you watch live on a smartphone or tablet. The Parrot Bebob Drone 2 even manages to set the angle of the camera remotely.

7. GPS

You can choose to purchase a drone with a GPS chip. This allows you to study the route of the flight simultaneously or later on a map. In addition, some types have a so-called Go home function. This will allow you to return the drone to the starting location. This happens on command or automatically, when the battery is almost empty, for example, or communication with the controller is no longer possible. The chance that you lose an expensive drone that way is extremely small.

By making use of GPS, certain quadcopters can also make more stable flights, because flight movements are corrected. Keep in mind that the presence of a GPS chip does not necessarily mean that all possibilities from this tip are possible. That is different for each type.

8. Bluetooth

Drones with a built-in bluetooth adapter are able to communicate directly with a smartphone or tablet. You can then operate the drone via a mobile app. The range of bluetooth is also limited to a maximum of twenty meters. This connection is therefore not so suitable for distant flights, but for smaller drones like the Parrot Mambo Minidrone that you mainly use at home is more than enough.

Lipo batteries are the new energy source for electrical drives. The first could not yet deliver as much peak power, but the new generations can easily supply a lot of power. The internal resistance is so low that even with a load of 100A the battery continues to supply 7 volts, where a NiMh has already collapsed to below 5 volts.
The internal resistance, which determines both the top speed of a car and the acceleration, is often less than 1/4 of the resistance of a top NiMh battery. That gives incredibly much speed to your car, in addition, the battery remains cold in normal use (little resistance = little loss = little heat development).
Furthermore, these batteries are super light (5000 mAh Lipo = +/- 270 grams = 200 grams lighter than a normal 3600 mAh NiMh).

C value:
There is still a big difference in Lipo batteries, not all lipos are equally suitable for a high current supply. With a Lipo battery belongs a “C” rating, as eg 15C, 20C, 25C. This “C” stands for the number of times the capacity that a battery can supply as a continuous flow. 20C means 20 x the Capacity. A 5000 mAh battery with a 20C rating can, therefore, supply 100,000mA or 100A continuously. 20C at 5000 mAh is the least you should have. However, it is not an absolute number, but a number relative to the capacity. A 25 C battery of 3000 mAh can supply 75A continuously, a 20C battery of 5000mAh can supply 100A continuously. Most of the batteries we offer are around 5000 mah at 25C, and may, therefore, be charged with 125A continuously, the peak currents may be even higher. This battery ‘ s are therefore very suitable for use in cars. At this time of writing, the normal Capacity for a Lipo with stick pack dimensions is about 5000 mAh. There are many brands of Lipo batteries, whereby that brand is often the brand of an importer/distributor/supplier (LRP, Nosram, Graupner, Robbe, Asso etc). The real manufacturer of the battery (eg Intellect) is hidden. As a result, a manufacturer is free to stick his own sticker on it, sometimes with very extreme capacity and C values. Do not be fooled by that, the differences are much smaller than the stickers make you believe! where that brand is often the brand of an importer/ distributor/supplier (LRP, Nosram, Graupner, Robbe, Asso etc). The real manufacturer of the battery (eg Intellect) is hidden. As a result, a manufacturer is free to stick his own sticker on it, sometimes with very extreme capacity and C values. Do not be fooled by that, the differences are much smaller than the stickers make you believe! where that brand is often the brand of an importer/distributor/supplier (LRP, Nosram, Graupner, Robbe, Asso etc). The real manufacturer of the battery (eg Intellect) is hidden. As a result, a manufacturer is free to stick his own sticker on it, sometimes with very extreme capacity and C values. Do not be fooled by that, the differences are much smaller than the stickers make you believe!

Discharge:
In the first place, they may never be completely discharged. that means in practice that if you fly with such a battery, and the power goes down, you have to stop. A LiPo of 11.1volt is composed of 3 lipo cells, and as soon as there is 2 on its lower limit and the other is not, and you would continue to discharge, the empty cell is immediately broken. This means that if you fly with a lipo battery, and the power goes down, you have to stop flying to prevent damage to the battery. Modern controllers often already have a special Lipo program, where the power is taken back when the battery voltage starts to drop, to prevent one of the cells from going below 3.2 volts. There are also special Lipo safety switches, which are placed between the receiver and the controller, which take over this task.

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The charging of a Lipo battery must also be done in a special way.
Where the voltage of a NiMh first rises during charging and then drops again in voltage when the maximum charge state is reached, (that is when a charger stops), a LiPo continues to increase in voltage during charging. However, the voltage of a lipo cell must never exceed 4.21 volts. If it does, the cell will be destroyed. A Lipo charger, therefore, works differently than a NiMH charger:

A NiMh charger charges with a constant amperage until the battery is full, then the charger will turn off. A Lipo charger initially charges with a high amperage, and as the voltage of the cell gets closer to 4.21 volts per cell, the amperage decreases. not only the total voltage is examined, but the voltage of each individual cell is also measured via the balancer connection. A lipo battery charger therefore not only has the thick plus and minus connection to which the controller or the charger is connected but also a few thin wires with a special small plug that goes to the balanced input of the charger. This allows the charger to measure the voltage of the individual cells and adjust the charging process accordingly. So even if 1 cell gets almost 4.21 V, and the other one does not yet, then the charging current is still taken back.
A LiPo battery can be brought to 90% of its capacity in a very short time (+/- 30 minutes), but after that, it can take quite a while before it is fully charged. In practice, charging is often stopped when the battery is so full that the charging current will noticeably go down because the last bit does not matter anymore.

Save:
Lipo batteries can best be stored semi-stored. This has to do with the chemical composition of the battery: Internal corrosion can occur due to the chemical difference between the anode and cathode. This phenomenon is smallest with a semi-charged battery. Good lipo chargers have a program where you can specify how much mAh can be charged. By draining the battery and setting this value to half the capacity, the charger will automatically turn off when half the capacity is reached.

The engine controller
A brushless motor controller or brushless ESC (Electronic Speed ​​Control) is used to a high speed of a brushless motor in drones. These act as an interface between the motor and the battery. Controlled by the throttle signal of an RC receiver, the brushless ESC provides variable power to the motor, which means that the speed is adjusted proportionally. Unlike a brushed motor, the force cannot be directly applied to a brushless motor. Instead, the controller will control every phase of the brushless motor for drone controlled and very intelligent manner, which ultimately results in a revolution. Brushless speed controllers have three motor wires, allowing them to connect to standard three-phase brushless motors.

Such a controller is equipped with Fets. These are electronic switches that can switch very high currents very quickly and with little loss. With brush motors the speed of the motor is regulated as follows: if you do not give full throttle, the controller sends the full current to the motor for a short time, then nothing for a while, followed by another period and a period not. So if you give eg 10% gas, then the controller sends all power to the motor 10% of the time, and 90% of the time nothing. In half gas 50% of the time everything and 50% of the time nothing. The current is thus controlled by the motor in a pulsed manner. At full throttle, all current is continuously sent to the motor, so there is no longer a pulse. This pulsing happens many times per second, and how often this happens is called the frequency, expressed in Hertz (1 Hz = 1 time per second). Many current simple controllers, which are based on the first developments of electronic controllers, have a frequency of 50 Hz. However, the modern state of technology has been improved, with much better batteries and high-speed motors that draw a lot of currents, that this is no longer sufficient for an adequate control of the currently available fast motors, and the average controllers also have a frequency of ± 3500 Hz. This results in less wear and tear on the engine (collector and brushes remain longer) and less heat is generated in the regulator and the motor itself. With a brushless motor, you can rotate the rotating field faster and faster to control the speed. have a frequency of 50 Hz. However, the modern state of technology has been improved, with much better batteries and high-speed motors that draw a lot of currents, that this is no longer sufficient for an adequate control of the currently available fast motors, and the average controllers also have a frequency of ± 3500 Hz. This results in less wear and tear on the engine (collector and brushes remain longer) and less heat is generated in the regulator and the motor itself. With a brushless motor, you can rotate the rotating field faster and faster to control the speed. have a frequency of 50 Hz. However, the modern state of technology has been improved, with much better batteries and high-speed motors that draw a lot of currents, that this is no longer sufficient for an adequate control of the currently available fast motors, and the average controllers also have a frequency of ± 3500 Hz. This results in less wear and tear on the engine (collector and brushes remain longer) and less heat is generated in the regulator and the motor itself. With a brushless motor, you can rotate the rotating field faster and faster to control the speed. and the average controllers also have a frequency of ± 3500 Hz. This results in less wear and tear on the engine (collector and brushes remain longer) and less heat is generated in the regulator and the motor itself. With a brushless motor, you can rotate the rotating field faster and faster to control the speed. and the average controllers also have a frequency of ± 3500 Hz. This results in less wear and tear on the engine (collector and brushes remain longer) and less heat is generated in the regulator and the motor itself. With a brushless motor, you can rotate the rotating field faster and faster to control the speed.
Every manufacturer has many speed regulator models available, most differ only by their amp rating and also the supply voltage (number of cells lipo). This is the maximum amount of current that they can continuously supply to an engine. The cell rating is the maximum number of cells that the speed controller can use. More than this can cause damage to the speed controller. The cell can be specified for both standard cells (NiMH and NiCD at 1.2V per cell) and lithium polymer cells (at 3.7V per cell). A regulator made for 5-12 standard cells are evaluated for 2-4 Li-Poly cells (4 Li-Poly cells give approximately the same voltage as 12 cells of NiCd or NiMh.).

Voltage Cut-off

When using lithium polymer (Li-Poly) batteries, it is important that the speed controller is set to a low voltage cut-off. This limits the discharge of the battery and prevents it from being damaged. The voltage cut-off can be automatic (the speed controller will detect how many cells are used) or manually. For manual settings it is possible to intervene (speed regulator is closed when the limit is reached) or soft (speed regulator reduces power) cut-offs. The soft cut-off should be set at 3.3 V per cell (9.9V total for a 3-cell pack), and the hard cut-off should be set at 3.0V per cell (9.0V total for a 3-cell pack). you can discharge up to 2.5 volts maximum. (taxed !!) (costs something lifespan). normally you can choose between 2.5 – 2.75 – 3 volts.

What is a BEC?
BEC stands for Battery Eliminator Circuit.

This electronic system, which is located in the controller, ensures that you do not need to connect an additional receiver battery. The receiver gets its power supply from the battery pack that is also used for flying.
When the flight battery is too empty to be able to fly, there is still enough “power” left for the receiver. BEC, therefore, ensures this.
A BEC is available in two versions, internal and external.
The internal BEC is part of the controller. The external BEC is a piece of electronics that is connected to the receiver next to the controller. important: do not connect internal and external be at the same time. Then something burns.

How does a BEC work?
A BEC is basically a regular “step down voltage regulator”. It will reduce your battery voltage from eg 11.1 Volts to ~ 6 Volts BEC voltage for a safe supply voltage of your receiver and servos.
What are the advantages of a BEC?
If you fly electric, a BEC is better than a battery in almost all cases. On average, the BEC weighs 10-20 times less than a receiver battery! Then you have to take into account the hassle of loading the receiver pack With a BEC, you only have to worry about recharging your main flight pack and then you are guaranteed a safe flight.

Which speed controller goes together with which engine?

Select a speed controller with a continuous current higher than or equal to that of the motor you want to use. This will ensure that the speed controller is able to handle the power requirements of your engine. If you use more than 3 or 4 Li-Poly cells, make sure that the controller has been explained, or it may be advisable to switch to a high voltage version. make sure your controller is suitable for the number of cells you want to use.2 poles to 10 + poles in / Outrunner Brushless motors.

The market is currently being “flooded” with brushless motors and controllers at prices that are at the level of an inexpensive brush motor.
The speed of the rotor and the temperature of the motor is determined by the motor gear used. the gear ratio between the main gear and the zipper. The engine manufacturer gives an advice on this on its website. It is nevertheless important to find out for yourself at which engine gear the combination runs nicely “round” and is not overloaded (hot engine and hot batteries). The best thing to do is to order extra motor gears when purchasing the kit. A starting point when looking for the right engine gear is: engine temperature maximum of 55 degrees C and the main rotor should easily be able to reach 1850-1900 rpm.
There is then flown with about 80% -85% power = about 1550-1700 rpm.
The speed is of course also tied to personal preference. There are pilots who only want to “rag” and therefore squeeze the maximum out of the helicopter and the engine.

 

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