By Joe Rich
Table of Contents
What is a RC Car servo
Servos play an essential role in the operation of RC (Radio Controlled) cars. Acting as the muscles of these vehicles, servos convert electrical signals into motion, allowing the RC car to perform various actions based on the user’s commands.
What is a Servo?
In an RC car, servos are typically tasked with two primary functions: steering and throttle control. The steering servo helps direct the car, moving the front wheels left or right based on the signals it receives from the radio transmitter. On the other hand, the throttle servo controls the car’s speed by adjusting the flow of fuel or the position of the electric motor controller.
The RC servos are very accurate in following the directions from the transmitter this makes the servo very precise in controlling the motion of the machines.
In simple terms, RC servos use onboard battery power to convert electrical commands into physical movement.
We have a article on how to make your RC car go faster click here to read
Types of servo
Not all servos are created equal. Understanding the different types of RC car servos can help you optimize your vehicle for performance and durability.
Analog Servos
Analog servos are the traditional type of servo used in RC cars. They work by sending pulses to the motor around 50 times per second, which controls the position of the servo arm. While analogue servos are generally less expensive than their digital counterparts, they tend to have slower response times and less precision.
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- Connector Wire Length: JR 180 mm (7.08in)
Digital Servos
Digital servos operate similarly to analogue servos, but they send pulses to the motor far more frequently, as much as 300 times per second. This results in faster response times and more precise control, making digital servos a popular choice for competitive RC racing. However, they do consume more power and are typically more expensive than analogue servos.
Coreless Servos
Coreless servos use a different type of motor that is lighter and more efficient than the motors used in standard servos. The rotating mass of the motor is less, resulting in faster response times and smoother operation. Coreless servos can be either analogue or digital.
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Brushless Servos
Brushless servos, like coreless servos, refer to the type of motor used. Brushless motors are more efficient and durable than standard brushed motors, offering longer lifespans and better heat dissipation. They are typically found in high-end, professional-grade RC car models.
Metal Gear Servos
Metal gear servos are designed for durability and strength. The gears inside the servo are made of metal, which makes them more resistant to wear and tear compared to plastic gears. These servos are ideal for high-stress, high-performance applications.
How does a servo work?
The performance of a servo is based on the control signals called pulsed signals that tell the motor where to go.
A servo plug has 3 wires – Power supply, ground and control signal. They usually follow colour codes.
|
Pin Number |
Signal Name |
Colour Scheme 1 |
Colour Scheme 2 |
Colour Scheme 3 |
|
(Futaba) |
(JR) |
(Hitec) | ||
|
1 |
Ground |
Black |
Brown |
Black |
|
2 |
Power Supply |
Red |
Red |
Red or Brown |
|
3 |
Control Signal |
White |
Orange |
Yellow or White |
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.
This can be achieved through pulsed signals called Pulse Width Modulation or PWM.
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.
The servomotor has a rotating shaft and potentiometer that detects it position.
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 move.
What servo should you get
Selecting the right servo for your RC car can significantly enhance its performance and longevity. Here are the key features you should consider:
1. Torque
Torque is the amount of force that a servo can exert and it determines how much load your servo can handle. High-torque servos are suitable for larger, heavier RC cars or those that require powerful steering or throttle actions. The unit of measurement for torque is typically ounce-inches (oz-in) or kilogram-centimetres (kg-cm).
These servos usually have metal gears fitted.
Servos with a high amount of torque are most useful on crawler steering.
2. Speed
Speed refers to how quickly a servo can move to a given position. Faster servos allow for more responsive control, which can be crucial in racing scenarios or complex manoeuvres. Speed is usually measured in seconds per 60 degrees (sec/60°)
So for example if your servo has a speed rating of 0.40 it will take 0.40 seconds to turn 60 degrees unloaded.
If you have a drift or a race RC car you would obviously a high speed rated servo.
The rating is calculated with the servo arm not connected to anything.
3. Size and Weight
The size and weight of the servo are important considerations based on the size of your RC car and where the servo will be placed. An oversized or heavy servo can affect the balance and overall performance of your vehicle.
4. Type: Analog vs Digital
As discussed earlier, analogue servos are less expensive but offer slower response times, while digital servos provide higher precision and faster responses but at a higher cost.
5. Voltage Rating
Servos operate at different voltage levels. It’s crucial to choose a servo that matches your RC car’s power supply to avoid damaging the servo or other components.
6. Gear Material
Servos come with either plastic or metal gears. Plastic gears are lighter and quieter but less durable, making them suitable for light-duty applications. Metal gears are more robust and resistant to wear, ideal for high-performance or heavy-duty use.
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7. Waterproof
If you plan to drive your RC car in wet conditions, choosing a waterproof servo can prevent damage from moisture.
Remember, there is no one-size-fits-all when it comes to choosing a servo. The best servo for your RC car ultimately depends on your specific needs, preferences, and the type of driving you plan to do.
How to Install a New Servo
Identify the mounting location: Locate the place where you will be installing your new servo. This is typically a pre-designated slot in the chassis of your RC car.
Prepare the servo: Attach the servo horn (the plastic or metal piece that moves the control surfaces) to your new servo. Be sure to centre the servo before attaching the horn.
Mount the servo: Place your new servo into its designated slot. Ensure it fits snugly and securely. Use the mounting screws provided with your servo to secure it in place.
Connect the servo: Connect the servo to your RC car’s receiver. The servo plugs into one of the channels on the receiver, typically labelled for steering or throttle.
Test the servo: Once everything is connected, turn on your RC car and test the servo. Ensure that it responds correctly to your commands from the transmitter.
Replacing an Old or Damaged Servo
Disconnect the old servo: Start by turning off your RC car. Then, carefully disconnect the old servo from the receiver.
Remove the old servo: Unscrew and remove the old servo from its mounting location. Keep the screws safe as you may need them to install the new servo.
Install the new servo: Follow the steps above to install your new servo.
Tips for Replacing a Servo
- Always ensure your RC car is turned off before starting any replacement process.
- Take note of how the old servo was installed before removing it. This will make it easier to install the new one.
- If possible, use a new servo that has similar specifications to your old one. This ensures compatibility with your RC car’s existing setup.
- Regularly inspect your servos for signs of wear or damage. Early detection can prevent potential performance issues or failures.
Servo Maintenance
Regular maintenance can significantly prolong the lifespan of your RC car servo and improve its performance. Here are some recommended steps:
Clean Regularly: Dust, dirt, and moisture can compromise the performance of your servo. Regularly clean your servo with a soft brush or compressed air to remove any debris.
Check Connections: Ensure that the servo is correctly plugged into the receiver and that all wires are intact. Loose or damaged connections can lead to erratic servo behavior.
Lubricate: If your servo allows for it, use a plastic-safe lubricant to keep the gears running smoothly. However, avoid over-lubricating as this can attract dust and cause build up.
Inspect for Wear: Regularly inspect your servo for signs of wear and tear, especially on the gears. Replace any worn-out parts promptly to prevent further damage.
Servo Troubleshooting
If you’re experiencing issues with your servo, here are some common problems and their potential solutions:
Unresponsive Servo: If your servo isn’t responding, first check the connections. Make sure the servo is correctly plugged into the receiver. If the problem persists, try plugging the servo into a different channel to rule out an issue with the receiver.
Erratic Movement: If your servo is shaking or moving erratically, there may be dust or dirt inside. Try cleaning the servo thoroughly. If the problem continues, it could indicate a more serious issue such as damaged gears or a faulty motor.
Servo Stuck in One Position: If your servo is stuck, it could be due to a mechanical blockage like a stripped gear or a jammed linkage. Inspect the servo for any visible blockages and remove them if possible.
Remember, while troubleshooting can fix minor issues, a severely damaged or consistently malfunctioning servo may need to be replaced entirely. Always consult your servo’s user manual or a professional
We have a article about diagnosing faults on a RC car click here to read.
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