Analog vs Digital Servo – Whats the difference?

To get the most from your car you need to understand the subtle differences in the component parts. Today we will look into Servos, in particular digital and analogue ones. So I can help you understand their fundamental differences.

What’s the difference between an analog and digital servo? The basic difference between the analog and digital servo is the speed of both of these motor types. Both these servo motors send and receive constant pulse signals. The analog servo sends 50 pulses per second while the digital servo sends up to 300 pulses per second.

Now that you know the basic difference between both servo motors, let’s learn some more details about analog and digital servo to get a better insight into how an RC car works. To all the new RC users, read on to get a deeper understanding of RC cars.

What is a Servo?

To define servo in simple terms, it is basically a control system. In technical terms of RC cars, it is an electronic device that controls RC cars by regulating its motion. In other words, servos are the mechanical motors in your RC cars.

The conversion of an electrical signal into linear or polar movement is the function of RC servos. Let’s study an example to understand it better.

A steering wheel of an RC car carries a control signal to the car, it is then decoded and sent over to the servo. The servo then rotates its drives shaft when the signal is received and this rotation is converted into the wheel steering.

A small but an important point to note here about ‘Hitec servos’ is that the black wire is the battery ground (negative), the red wire is the battery power (positive), and the yellow or white wire is the receiver signal.

Right now, this seems like a long and complicated process but this process happens in a matter of seconds or even less than that.

Also, let’s discuss another important question while we are discussing servos. What servo should you use for your RC car? There are two main factors you need to keep in mind for choosing servos which are speed and torque.

We suggest you to go for the high torque servos if you are confused. It is also wise to follow the guidelines of the kit manufacturers, as they give suggestions according to the specifications of your RC car.

If you had a large powered aircraft on the other hand, micro servos are not appropriate even though they offer 38oz/in of torque like HS-81. Additionally, smaller servos are more fragile than standard servos because of thinner gears.

What is a Digital Servo?

In a digital servo, incoming signals are processed and converted into servo movement. These signals are received by a microprocessor. The length and amount of power of the pulse is then adjusted to the servo motor. Through this, optimum servo performance and precision can be achieved.

As mentioned above, digital servo sends these pulses at a much higher frequency which is 300 cycles per second. With these rapid signals, the response of the servo is pretty quick. The increase in the motor’s speed; eliminates the deadband. The digital servo provides a smooth movement with higher power consumption.

Since we are talking about digital servos here, we would like to give you a little update on its latest model HS-50. This model is a super feather servo, a modern miracle in miniaturization and it has been engineered with precise components to provide a long-lasting free service.

It operates exclusively at 4.8 volts (4 cells). From indoor RC and hand launch gliders to ultra-small electric park and yard flyers, it’s an excellent choice for any micro application.

What is an Analog Servo?

This a standard type of servo motor. In an analog servo, the speed of the motor is controlled by applying on and off voltage signal or pulses. The regular pulse voltage range is between 4.8 to 6.0 volts and this is constant.

For every second the analog servo receives 50 pulses and there is no voltage sent to the servo when on rest.

If you have an analog servo, you will be able to notice that the servo lags in reacting to small commands and cannot get the motor spinning fast enough. A sluggish torque is also formed in an analog servo, in other terms this is also called deadband.

Now that you have an idea about what is an analog and digital servo, you can decide for yourself that which servo motor will you prefer for your car.

What are the different RC Servo Sizes?

By now you have an overall idea about RC cars and that they come in different models and sizes. Just like this, the servos of RC cars have a variety of sizes and they are categorized into six standard sizes. In the table below you can see all the sizes with their specifications.

Servo Size Weight Range Typical Servo Width Typical Servo Length Typical Applications

 

Nano Less than 8g 7.5mm 18.5mm Micro airplanes, indoor airplanes, and micro helicopters
Sub-Micro 8g to 16g 11.5mm 24mm 1400mm wingspan and smaller airplanes, small EDF jets, and 200 to 450 size helicopters
Micro 17g to 26g 13mm 29mm 1400 to 2000mm wingspan airplanes, medium and large EDF jets, and 500 sizes helicopters
Mini 27g to 39g 17mm 32.5mm 600 size helicopters
Standard 40g to 79g 20mm 38mm 2000mm wingspan and larger airplanes, turbine powered jets, and 700 to 800 size helicopters
Large 80g and larger >20mm >38mm Giant scale airplanes and jets

 

These are the general servo sizes and their specifications for your knowledge. If you already own an RC car then you can take out the servo from the car and check its size. When you go to buy a new RC or even buy online, check all its specifications to find the details about its servo type and size.

What is a Typical Servo Frequency?

The typical RC servo frequency is 50H.z. This means that the position of the servo is refreshed 50 times in a second. For most standard servos 120H.z is the limit. In addition to this, in the hitec servos 3-4V peak to peak square wave pulse is required. 0.9ms to 2.1ms is the pulse duration with 1.5ms as center.

The frequency of the servo can notably vary depending on different brands, models, and its components. There are fast rated and slow rated servos, if your servo is fast rated then you can refresh the frequencies by setting it on slower or speedy rates.

Check all the specifications of your servo model before setting the frequencies.

Which One is More Expensive, Digital or Analog?

Digital servo is more expensive than analog. It is obvious from the names that which one is more expensive. In the aforementioned questions, we have already discussed in detail about both these servos.

The reason why digital servos are more costly is that they offer high-quality performance with higher speed consumption.

But you should also keep in mind that there are variations in digital servos as well. You can also get low-spec digital servos which are less expensive. While we are comparing these servos based on their price and quality, let me tell you that there are high-spec analog servos as well which provide better performance.

Here is an expert opinion for you on digital servo prices. Remember, earlier in this article we talked about the brand-new model of digital servo that is HS-50? Well, this model’s prices start from $7 and which is incredibly reasonable for all the RC car fans out there.

So, the next time you decide to buy a whole new RC car or maybe you just want to change its servo, you already know your options. You can select any one of these options based on your budget and requirements.

Is a Digital Servo More Accurate or Precise Than an Analog?

From such an elaborate discussion in the above paragraphs, you must have guessed by now that digital servos are more accurate than the analog servos.

This is because a digital servo has a swift and smooth output. Additionally, it has a pre-programmed ability for the deadband and peak voltages. Therefore, it can be concluded that digital servos are much more efficient than their analog counterparts.

Before switching to a digital servo, weigh your options carefully. You should consider the price, the disadvantages, the quality, your budget and your level of expertise before upgrading to a digital servo.

Why Do Digital Servos Have Higher Power Consumption?

Remember when we were discussing the digital servos’ working mechanisms and how it consumes an excessive amount of power? You must be wondering why does this happen? Well, the higher power consumption is because of the frequent on/off signals it transmits to the microprocessor and the peak voltages it provides.

With the ability to optimize the digital servo performance, you have higher control over the acceleration and deceleration of your RC car.

The digital servo is more efficient, precise, and potent than the analog servo but its high power is its biggest disadvantage.

Are you thinking to switch to the analog servo after getting to know all this? If you are, then here is a helpful suggestion. Use a capable battery or switch to BEC circuit to power the analog servo.

What Do the Servo Speed and Torque Settings Mean?

The servo speed can be defined as the amount of time the servo’s arm takes to transmute a stipulated electrical pulse. The servo speed is often stated in the specifications of your RC car as well as on the servo itself. Because of torque settings, the amount of turning power will be the same when you turn the wrench.

The servo speed and torque settings are closely connected to each other. Whether you want to speed up your RC car or go slower, the torque gives off a refreshing signal accordingly. This is what holds the servo’s arm or speeds it up against the dynamic forces.

Here is some useful information on torque and servo speed. One servo is geared for speed created hitec while some torque is sacrificed, while others are created to give high torque and sacrifice the speed. The servo products like 525/545, 625/645, 925/945 are the perfect examples.

What are the Limitations of an Analogue Servo?

After understanding what is an analog servo and its advantages in the previous questions, let’s look at some of its limitations:

  1. Because of the production of additional deadband in an analog servo, its performance becomes slow. For higher performance, it needs longer pulses.
  2. The brake system suffers because the power of torque is much lower. The acceleration and deceleration also get
  3. These analog servos may work in modern RC cars but not in the helicopters and planes.
  4. Another one of its limitations is that it is non-programmable. So, you cannot optimize its efficiency nor improve it.
  5. It is not suitable for off-road racing or air-borne RC vehicles as it produces a low amount of torque.

What are the Limitations of a Digital Servo?

We know that digital servos are superior than analog servos in many ways. But they do have some limitations that we should consider before deciding which one is suitable for your car.

  1. If you are switching from analog to digital or if you are entirely new at RC car racing and maintenance then digital servos can be expensive for you. Even if your old digital servo somehow got damaged and you are buying a new one, you will still feel that it’s But the results that you receive outweigh the costs later.
  2. As you know that in digital servos higher amount of voltage pulses are sent in per second. Due to this reason, the battery is drained quickly. In other words, it consumes a greater amount of power and this is one of its major limitations.
  3. There is another limitation of having a digital servo. Since you know that it is programmable, you need to operate it carefully because if you don’t manage the torque carefully, the moment the servo torque gets higher it will reset to staying dead and can cause a crash.

Now that you are aware of all the benefits and limitations of both servos, which one have you decided to invest in? By keeping your RC car specifications in mind, decide smartly about the type of servo suiting best to your RC vehicle.

What Voltage Do Servos Run On?

The standard servo voltage ranges between 4.8 to 6.0 volts. The voltage depends on the type of batteries you are using and the servos. Analog servos use up less voltage than digital servos as they have a higher battery usage capacity.

Another point to observe is the number of servos you are using. You need to get the battery packs according to the voltage specified on your servo. Be aware that when alkine batteries are used in “coreless” or digital servos, they often perform terribly.

What is Servo Deadband?

The amount of input required from the TX Stick movement for a servo to respond is a servo deadband. A greater amount of stick movement is needed for a higher amount of deadband. Since analog servos produce deadbands, their usual deadband amount is 8us but for quality performance of servos 1~3us of deadband is needed.

Do you need an advance caliber performance for your analog servo? You can get its deadband upgraded to enjoy speedy operations.

What Does Coreless Servo Mean?

It mainly refers to the armature of the servo motor. A Coreless servo is free of the iron core as the standard servo motors consist of an iron core armature wrapped with the wire.

A bell of thin wire mesh forms a cup that spins around the outside of the permanent magnets in a coreless servo when the electricity is supplied, eliminating the heavy iron core. As a result, a coreless servo gives smoother operation and fast response time.

Other than analog and digital servos, you can also consider coreless servos for your RC car. It will give you an improved functioning, your car will run smoothly as this servo has a quick response time.

Some people are comfortable with analog servo because of its power optimizing capability, while others use digital servo because they love high power and speed. Remember that, both these servos are valuable in their own ways.

Now that you have all the information about RC cars and its servos, it is totally up to you to decide that whether you need analog servos or digital servos.

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