Servo motors are a specialized kind of motor which can be controlled to move to a specific angle instead of continuously rotating like a DC motor. Instead of a hex output shaft like the DC motor, servos have an output spline. A spline is a specific groove pattern cut into the shaft which allows the rotation of the servo motor to be transmitted to the attached Aluminum Servo Horn (REV-41-1363) or Servo Adapter. Splines are like keys, so only matched types will fit together. The REV Robotics Servos all use a 25T spline pattern. If the gears or spline of the REV Robotics Smart Robot Servo (REV-41-1097) become damaged, they are replaceable using a Replacement Gear Set (REV-41-1168).
Common servo motors take a programmed input signal range and map that to an angular range. For example, for a servo with a 270° range, if the input range was from 0 to 1 then a signal input of 0 would cause the servo to turn to point -135°. For a signal input of 1, the servo would turn to +135°. Inputs between the minimum and maximum have corresponding angles evenly distributed between the minimum and maximum servo angle.
REV Robotics Servo Adapters fit 25T spline servos like the REV Robotics Smart Robot Servo. In addition to the variety pack of generic servo horns which come with the Smart Robot Servo, there are four other custom servo adapters which make using servos with the REV 15mm Building System easy.
Servo Gear Adapters convert a 25T servo into 15 tooth Delrin gear which is compatible with the other REV Robotics Plastic Gears.
Servo Shaft Adapters convert a 25T spline servo output shaft into a female 5mm hex socket. This adapter can be used to drive a hex shaft directly.
Aluminum Servo Horns have a tapped hole pattern that can be directly mounted to any of the REV Robotics gears, wheels, or sprockets with the Motion Pattern.
Aluminum Double Servo Arms (REV-41-1820) have two tapped holes that can be directly mounted to any of the REV Robotics extrusion, channel, or brackets.
Teams should be aware of the number of servo motors they attach to each Hub. The Control Hub (REV-31-1595) and Expansion Hub (REV-31-1153) only can handle 5 Amps through all 6 servo ports. The maximum current a servo will draw is 2.0 Amps, called the stall current. A servo will draw the stall current when it is applying the maximum force, but it is not moving. For example, a servo can stall when a mechanism needs to hold something or a heavy object blocked the path of the servo motion.
Normally servos do not draw the maximum current, but teams do not know what might happen during matches. To protect against overdrawing the current on the Hub, only attach 2 servos to a Control Hub or Expansion Hub. Teams can safely use 4 servos: 2 servos on the Control Hub and 2 servos on the Expansion Hub.
If more power is required, consider using the REV Servo Power Module (REV-11-1144). It is a 6V 90W power injector that enables the use of high-power RC servos in applications where a robot controller cannot provide adequate power.
Switching between continuous rotation, standard servo, and custom angular modes is easy as pressing a button. The SRS Programmer can not only program the SRS, but it is also acts as a standalone servo tester for any standard RC servo.
The REV Robotics SRS Programmer includes the following features:
3 programming modes
Continuous rotation
Angular limits
Reset to factory defaults
Test modes
Automatic sweep
Manual position/direction
Intuitive operation with LED feedback
Self-powered
Power-off reminder
† Not Included
The SRS Programmer has several operating modes for configuring and testing the REV Smart Robot Servo. The following sections describe each operating mode in detail.
Before using the SRS Programmer to switch modes or program your servo motor, check that the batteries are not low. If your SRS Programmer has not been used in a while, please put in a fresh set of batteries to avoid potentially corrupting the firmware of your servo motor.
Follow the steps below to switch a REV Smart Robot Servo between Continuous Mode and Servo Mode. The figure below shows the process to select Continuous Mode.
Connect the SRS to the programmer.
Turn on the programmer.
Slide the mode switch to the desired mode: C - Continuous, S - Servo.
Press and release the PROGRAM button once.
The PROGRAM LED should blink and then stay solid indicating success.
Follow the steps below to set the angular limits for the Servo Mode. The figure below shows an example of setting a left and right limits at -30° and +60° respectively.
Connect the SRS to the programmer.
Turn on the programmer.
Slide the mode switch to S position.
This step is optional, but recommended to make it easier to see the valid limit ranges. Please refer to the SRS User's Manual for more information about the valid limit ranges.
Press the PROGRAM button to center the servo at 0°.
Press and release the TEST button once to leave the test mode.
Manually rotate the servo to the desired left limit position.
Press and release the LEFT button. The LEFT LED will illuminate if the position is valid.
Manually rotate the servo to the desired right limit position.
Press and release the RIGHT button. The RIGHT LED will illuminate if the position is valid.
After both limits are set, press and release the PROGRAM button. The PROGRAM LED should blink and then stay solid indicating success.
Follow the steps below to reset the Smart Robot Servo to its default mode and limits. The figure below shows the process to reset to defaults.
Connect SRS to the programmer.
Turn on the programmer.
Slide the mode switch to S position.
Press and hold the PROGRAM button for at least 5 seconds.
The LEDs will blink and then the PROGRAM LED will stay solid indicating success.
In either Continuous or Servo Modes, pressing and releasing the TEST button cycles through the two test modes:
1st press - Automatic Sweep Mode
2nd press - Manual Test Mode
3rd press - Return to default state
The section below will cover the two different test modes.
In Automatic Sweep Mode, the SRS Programmer will automatically sweep the SRS through motions appropriate for its configuration. the table below describes the behavior based on the configured mode.
In Manual Test Mode the LEFT, PROGRAM, and RIGHT buttons control the movement of the SRS. The table below describes how the SRS will behave based on the configured mode.
If the SRS Programmer is left on for an extended period of inactivity, it will blink every LED as a reminder to shut off power.
The REV Robotics SRS Programmer () is the key to unlocking all the smart features of the Smart Robot Servo (SRS) ().
Start with the SRS already configured in Servo Mode, see section for instructions.
Press and release the TEST button twice to enter Manual Test Mode (see for more information).
Mechanical Specifications |
Dimensions | 70.5mm x 64.5mm x 35.5mm |
Weight |
Electrical Specifications |
Power Source | 4 AA batteries |
Power Output | 6V nominal |
Logic Level (Signal Out) | 3.3V |
Output Pulse Width Range | 550μs – 2450μs |
Center Pulse Width | 1500μs |
Servo and Programmer Mode | Behavior |
Continuous Mode (C) | Sweeping direction and speed |
Servo Mode (S) | Sweeping between limits |
The Smart Robot Servo is a metal-geared servo with the ability to replace the metal-gears it they become damaged during use. Damage to the gear set can occur if the servo receives a shock load to the system. This guide explains the process of removing and replacing the gears in the REV Smart Robot Servo (REV-41-1097) using the Replacement Gear Set (REV-41-1168).
To replace the gear set in the Smart Robot Servo you will need the following items:
Smart Robot Servo (REV-41-1097) – QTY 1
Replacement Gear Set (REV-41-1168) – QTY 1
Phillips Head Screwdriver (PH0) – QTY 1
The replacement gears are shipped un-greased. They need grease to run smoothly, so make sure the is enough grease in the gearbox, and if not, add equivalent of ~1/4” diameter sphere of grease to gears in the gearbox.
The REV Robotics Smart Robot Servo (SRS) (REV-41-1097) is a configurable metal-geared servo that takes the guesswork out of aligning and adjusting servo based mechanisms. One SRS can be used as a standard angular servo, a custom angular servo, and a continuous rotation servo by simply changing its settings.
The REV Robotics Smart Robot Servo includes the following features:
Default operation
270° motion over full input pulse range
Metal gears
Smart features
Programmable with REV SRS Programmer (REV-31-1108)
Servo Limit Mode
Set right and left angular limits
SRS will not move past limits
Continuous Mode
SRS spins continuously
Speed and direction set by input pulse
Input Pulse:
Min: 500μs
Center: 1500μs
Max: 2500μs
The REV Robotics SRS comes with the following:
REV Smart Robot Servo
Servo horn (arm) assortment
Servo horn mounting hardware
Is a servo the right actuator for your mechanism? See the Choosing an Actuator section to learn more.
Out of the box, the SRS operates as a 270° servo. However, the REV SRS Programmer can reconfigure the SRS to set angular limits or switch it into a continuous rotation mode.
For more information on how to use the SRS programmer to change the servo modes see the SRS Programmer section
The default range for the SRS is 270°. This range is mapped to an input pulse range of 500μs to 2500μs with 1500μs as the center point. The image below describes the pulse-to-angle relationship.
The SRS can be configured with the SRS Programmer to operate in a continuous rotation mode. In this mode, the same input pulse range is mapped to direction and speed. The table below lists the pulse mapping for direction and speed.
The SRS can be easily configured with the SRS Programmer to limit right and left motion at two user-defined angles. Input pulses that occur past the limits will be ignored and the SRS will hold the limit angle. Any two angles can be set as limits as long as the left limit is left of the center dead band and the right limit is to the right of the center dead band. The table below shows the valid regions for left and right limits.
Once valid limits are programmed, the SRS will ignore any pulses that exceed the limits and hold the limit angle. For example, the image below exhibits what would happen if a left limit of -30° and a right limit of +60° was set.
The Servo Power Module has two screw terminals for 12V power input. It is recommended to use ring or fork terminals designed for #6 or M3 screw terminals.
Using an appropriate wire gauge, 18 AWG or larger, tightly crimp either a ring or fork terminal on the wire. Insert the crimped terminal into the screw terminal and tighten the screw.
The input and output channels accept standard 3-wire 0.1” pitch servo/PWM cables. Please refer to the figure above or the case markings for proper orientation.
Each channel has a corresponding status LED that will indicate the sensed state of the connected PWM signal. The table below describes each state’s corresponding LED pattern.
If the Servo Power Module detects a total output current larger than 15A it will enter a shutdown mode where the 6V output is disabled until the over-current condition has remedied. While in shutdown the blue power LED will turn off, dim, or flicker indicating the over-current condition is still present.
In the case of frequent over-current shutdowns, ensure that the total stall current of all connected servos does not exceed 15A.
The REV Servo Power Module () is a 6V 90W power injector that enables the use of high-power RC servos in applications where a robot controller cannot provide adequate power.
Stall torque (at 6V)
13.5 kg-cm / 187.8 oz-in
Speed (at 6V)
0.13s/60º
Maximum angular range
270º
Gear Material
Brass
Spline Type
25T
Dimensions
40.2mm x 20.0mm x 38.0mm
Weight
2.05oz.
Min
Nominal
Max
Voltage Rating
4.8V
6.0V
7.4V
Stall Current (at 6V)
2.0A
Key Terms | Key Metrics |
Nominal Input Voltage | 12V |
Operating Voltage Range | 7.0V - 20V |
Minimum Startup Voltage | 9.0V |
Output Voltage | 6V |
Number of Channels | 6 |
Max. Total Output Current (across all Channels) | 15A |
Max. Total Output Power | 90W |
Size | 3.6” x 1.52” x 0.81” |
Weight | 2.0oz/57g |
State | Pattern |
No Signal | Blinking Amber |
Left/Reverse Signal | Solid Red |
Center/Neutral Signal | Solid Amber |
Right/Forward Signal | Solid Green |
Step 1
Remove the four screws that hold the upper casing.
Step 2
Remove the upper casing. Orient the servo so that the servo wire is to the left-hand side.
Step 3
Remove the the reduction and output gears. The last silver gear is removed with the axle as one unit.
Step 4
Remove the axle pin from the silver gear and replace gear if necessary. Note: replacement gears are shipped un-greased. Please grease all replacement gears before installing.
Step 5
Attach silver gear to the axle pin.
Step 6
Place the new silver gear onto the servo unit making sure contact with the servo motor's output shaft first, then slide the axle into the axle opening.
Step 7
Place the second gear in place. Make sure the lower level of teeth on this gear mesh with the upper level of teeth on the silver gear.
Step 8
Next place the output shaft gear in position. Make sure to align the slot in the gear with the tab on the servo.
Step 9
Once the output shaft is in place correctly, it should be seated securely but not touching any other gears.
Step 10
Place the final gear on the middle shaft. It should first mesh with the output shaft on its lower set of teeth, and then its upper teeth will mesh with the gear on the right shaft.
Step 11
Finally, reattach the top plastic cover, making sure to place it directly down on top of the gears so that they don’t become misaligned. Reattach the 4 screws and the servo is ready to operate.