How do servos work rc

Power Consumption! All those hundreds thousands of power pulses per second use up more battery power than an analog servo would. That said, it can be a big issue for your BEC internal or external or a voltage regulator all of which have a finite maximum current output. For more information about this potential problem, please see the Digital Servo article. So yes, digital RC servos are much better than analog. You can still fly a flybared RC helicopter with analog cyclic servos, but once you switch over to digital, you will likely never go back.

As I said, most if not all these days need to be paired with fast digital servos to work correctly — no exceptions! Remember those speed and torque specifications I talked about earlier You will find analog servos that have better speed and torque ratings than some digital servos; so why not get one of them over a more expensive slower digital?

Remember, the analog servo is slow to respond and provides little torque during small, fast command inputs not to mention poor holding power. Those good looking specifications are given at full stick movement when the servo has ramped up to full speed and torque. The slower spec digital servo in this case will still provide much more speed and torque where it's needed most.

One step up from the 3 pole is the 5 pole servo motor. As you can imagine, two more wire windings will give a 5 pole motor quicker acceleration and more torque on start up.

You know by now the faster the servo ramps up to speed and the more torque it produces; the better it is for most helicopter applications. Well, improving the electric motor itself will produce more speed and torque too; coupled with digital technology, the resultant speed and torque are indeed impressive.

Still, a 3 or 5 pole motor no matter analog or digital power, is limited by its high rotational mass Time to go on a diet! A standard 3 or 5-pole wire wound servo motor uses a steel core with wires wound around the core, with the commutator at one end. This "armature" spins inside the motor body which has permanent magnets attached. As you may recognize, that big armature core, commutator, and all that wire weighs a fair bit and has a good deal of rotating mass.

When voltage is applied to turn the motor, it has to first overcome this weight to get things turning — it is slow to accelerate due to inertial mass. Once up to speed, it also continues to turn for a while when the voltage is removed — it is slow to decelerate or reverse direction again due to higher inertial mass.

This is also quite hard on the brushes and commutator. In a Coreless design, the heavy steel core is eliminated by using a light weight wire mesh that spins around the outside of the magnets within the body of the motor. The wire mesh rotating armature is simply made from thin copper wire strands along with the motor shaft and commutator on the back end. The coreless motor armature weighs a fraction of what a wire core wound does.

This results in quicker acceleration and deceleration. The result is more available torque, and faster response time. I personally feel coreless motors offer the best servo performance - even over brushless at least from the stand point of fastest acceleration and least amount of deadband.

Exactly what a servo demands out of its motor. My own view point is the "average" heli flier is going to be best served bang for the buck performance wise with good quality digital coreless servos while also saving a few bucks in the process. If you are wanting the best efficiency, smoothness, and lifespan; ante up the coin and go for brushless.

I've been very happy so far with that compromise. One other consideration is the tail servo. You will therefore often see people using brushless tail servos, along with conventional brushed or coreless servos on the swashplate as a budget driven compromise.

I have also done this with excellent results. True, most modern day RC radios have channel reversing and that's the obvious way to reverse the travel direction of an RC servo. However, some very basic radios don't. Moreover, you will sometimes find the need to control more than one servo from the same channel; retracts or ailerons come to mind. There are commercially available servo reversers also called servo inverters , that you plug "in-line" with the servo to reverse it.

See below:. You can also reverse many RC servos yourself for free, very easily by swapping the motor wires and potentiometer wires from side to side. The video I made below shows the process. You will notice when servo shopping, many specifications list if the servo has bearings and the number of bearings — usually 1 or 2. These bearings are used on the main servo output shaft instead of a simple bushing. The advantages of having ball bearings on the output shaft in a servo are pretty much the same as I talked about in the Bearing Section of best RC helicopter features — less friction and slop.

Most quality RC servos, even lower cost ones these days will come with at least one bearing — this will be located on the servo output shaft where it exits the servo, this is where most of the side loads will occur.

Better more expensive servos will use two bearings to further improve overall slop free performance. With today's high torque and speedy digital servos, combined with high force load RC model applications, metal gears and output shafts are getting more and more common place.

They are a popular choice for several reasons, but improved strength is the obvious one. There are three downsides to metal gears however. They weight a little more than plastic or nylon gears, they wear out a little faster, and they are more expensive to replace. Yes, most servos have replaceable gear sets so you can easily replace the gears, but some metal gear sets are approaching half the cost of just getting a new servo. The best metal gear servo's on the market these days are using titanium or various exotic titanium alloy gear sets and this drops the weight down and improves gear wear characteristics substantially, while increasing the cost as well.

All that said, don't think for a second that by using metal geared servos, you will never strip out a gear set. Here is a simple, low-cost, high quality servo for all your mechatronic needs. This servo is very similar in size and specifi…. This is a SparkFun exclusive!

These are 12" long, 26 AWG jumper wires terminated as male to female. Use these to jumper from …. In particular, notice that power to the servo motor is supplied from the VIN pin, which bypasses the onboard regulator. The onboard regulator in insufficient to drive anything but the smallest of servos.

You'll also notice that the project is powered with a 5V wall adapter. On the author's workbench, performance was marginal when the board was powered by the USB port. Pay particular attention to the attach call on line It is using the optional min and max parameters, to constrain the pulses to the to microsecond 1 to 2 millisecond range.

As noted in the Range Constraints section above, driving a servo outside that range may damage the servo. The servo library also has a few other limitations. Most notably, it overrides analogWrite on pins 9 and For more information about the library, check the Arduino reference pages. If things don't seem to be quite right, please look through the troubleshooting section. Having programmed a servo example from scratch in the last section, there's another way to deploy servos that doesn't require any programming.

The SparkFun Servo Trigger is a small board dedicated to driving hobby servos. It has trimpots that allow you to set the servo positions and jump between the positions by actuating a switch. It is available in standard and continuous rotation versions.

For more detailed information about the Servo Triggers, consult their respective hookup guides. Regardless of how you're driving it, servos sometimes require a little extra attention to get working. Here are a few troubleshooting tips. Need Help? Mountain Time: Shopping Cart 0 items. Product Menu. Today's Deals Forum Desktop Site. All Categories. Development Single Board Comp.

Contributors: MikeGrusin , Byron J. Introduction Servo motors are an easy way to add motion to your electronics projects. Heads up! If you're in doubt about your color scheme, check the documentation -- don't plug it in backwards! A Handful of Distinctions When you're shopping for servos for your project, there are several parameters that you'll want to keep in mind. Range Constraints The 1-to-2 millisecond pulse range is more of a convention than a hard-and-fast standard.

Deploying Servos Traditional RC Application As we stated in the introduction, the usual application of hobby servo motors is for steering radio-controlled vehicles. Controlling a Servo with Arduino Because they move on command, servo motors are an easy way to add motion to any project.

Materials To build this example, you'll need the following materials. When there is a pulse from the control signal, sent by the driver from the transmitter, it applies current to the motor that makes the shaft move until the potentiometer indicates that the position is in line with the width of the pulse. That movement is what the driver has asked for to control the model around the twists and turns of an RC car track. In the beginning servos used to come only in analogue form.

Now they come in a digital form which is the common standard for all servos in the s. Before we determine which type of RC servo is better, let us have a look at the functionalities of both these types. The components, circuit, mechanism, everything remains same. The whole difference is in the way the PWM signal is processed.

Analogue systems used 50 pulses per second. Digital systems receive over pulses per second! This not only improves the accuracy of the servo, it also improves the speed of the movement. The digital servos have many more advantages over analogue servos. They are fast, have quick response, higher resolution and more power.

More power means more power consumption from the onboard battery. While the power supply wires provides voltage to the plug and the ground does what is supposed to do, the control signal is the wire that communicates the messages to motor and tells it where to go. The usual frequency of these PWM signals is 50 Hz, which is every 20 milliseconds. In simple terms, the servo is updated every 20 milliseconds.

When there is a pulse from the control signal, it applies current to the motor that makes the shaft move untill the potentiometer indicates that the position is in line with the width of the pulse. This is a feedback from where the pulse width tells the motor about the desired position and potentiometer makes the shaft the necessary move. In the beginning just like many electronic devices, servos used to come only in analogue form, and now with progress like everything else, they come in a digital form too.

Before we determine which type of RC servo is better, let us have a look at the functionalities of both these types. The components, circuit, mechanism, everything remains same. The whole difference is in the way the PWM signal is processed. The digital servos have digitally controlled pulses which are far faster than the analogue servos. Digital servos though have the same parts as analogue including the wire plug, the difference is the way PWM is processed, as discussed earlier.

The digital servo has a small microprocessor that receives the signals and process them into a high power pulses to servo motor. This is being minimised now a days with the manufacturers bringing out higher powered batteries, but power consumption is definitely on the higher side with digital servos.