node-red-contrib-servo

node-red-contrib-servo is a Node-RED node designed to control servo motors by stepping from one position to another. It receives values via topics for from, to, and duration to control the motor's movement. This node handles the precise positioning of servo motors and includes error handling to ensure the input values are valid.

Features

• Configurable via Topics: Specify the from, to, and duration parameters dynamically using MQTT or inject nodes.
• Start/Stop/Resume Functionality: Control the motor's movement using commands like start, stop, and resume.
• Error Handling: Ensures that the from, to, and duration parameters are valid numbers before initiating motor movement.
• Accurate Movement: Avoids unnecessary resets of the servo motor to its home position after stepping, maintaining its accuracy.

Installation

Install via the Node-RED palette manager or run the following command in your Node-RED user directory (typically ~/.node-red):

npm install node-red-contrib-servo

Usage

1. Send Control Messages:

   • Use start, stop, and resume commands to control the servo motor.
   • Send these commands with a true payload via MQTT or inject nodes.

2. Set Movement Parameters:

   • Send numeric payloads for from, to, and duration to set the servo's stepping range and speed.

Example Flow

Here’s a simple example flow to control the servo motor:

[{"id":"inject_start","type":"inject","z":"flow_id","name":"Start","props":[{"p":"payload","v":"true","vt":"bool"},{"p":"topic","v":"start","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"start","payload":"true","payloadType":"bool"},{"id":"inject_stop","type":"inject","z":"flow_id","name":"Stop","props":[{"p":"payload","v":"true","vt":"bool"},{"p":"topic","v":"stop","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"stop","payload":"true","payloadType":"bool"},{"id":"servo_node","type":"servo","z":"flow_id","name":"Servo Controller","from":"","to":"","duration":"","x":400,"y":200,"wires":[[]]}]

In this flow:

• Use an inject node to send the start, stop, and resume commands.
• Use another inject node to send numeric payloads for from, to, and duration to control the servo motor.

Topics

• start: Starts stepping the servo motor from the from position to the to position within the defined duration.
• stop: Pauses the stepping.
• resume: Resumes the stepping from where it was paused.
• from: Defines the starting position for the servo (numeric payload).
• to: Defines the target position for the servo (numeric payload).
• duration: Defines the time (in milliseconds) it takes for each step (numeric payload).

Error Handling

The node will check the input parameters for validity:

• from, to, and duration must all be valid numbers.
• If an invalid value is received, an error message will be displayed in the debug panel.

Node Status

• Blue Dot: Ready to receive commands.
• Blue Ring: Stepping in progress.
• Red Ring: Stepping paused.
• Green Dot: Stepping completed.

License

This project is licensed under the GNU General Public License v3.0. See the LICENSE file for details.