node-red-contrib-countdown

node-red-contrib-countdown is a simple countdown node.
It starts a countdown timer on a received input msg and decreases the counter value (at the first output) until the countdown timer elapses. The countdown can be stopped at any time. Also the countdown timer can be set to any new countdown value at any time to reload the timer with a specific value.

The output can emit a msg at its first output with an arbitrary msg.payload contents at the start of the timer as well as at the stop of the countdown timer.
At the second Output the node emits the remaining counter value every second.

The node's output msg can optionally contain an arbitrary topic string.

Loosely based on prior work by Neil Cherry: https://github.com/linuxha/node-red-contrib-mytimeout

!node-appearance
Fig. 1: Node appearance

Installation

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* Via Manage Palette -> Search for "node-red-contrib-countdown"

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* go to the Node-RED installation folder, e.g.: ~/.node-red
* run npm install node-red-contrib-countdown

Usage

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!node-settings
Fig. 2: Node properties

#### Countdown (secs) property
Set the Countdown value to the desired countdown time in seconds. The timer will start with this countdown value to decrease the timer value (countdown start value).

#### Topic
The Topic can be set to any string value. This string is added to the output msg as an additional element msg.topic.

Note: No value is given to the topic.

#### Timer On payload, Timer Off payload
Set the Timer On payload to any payload type and value which is sent when the counter starts.
Set the Timer Off payload to any payload type and value which is sent when the counter elapses.
In both cases, also nothing to be emitted may be chosen.

#### Flags
You can configure the timer to
- restart (reload) the timer to its countdown start value during the count down whenever a msg is received at the node's input.
- activate the ability to set the timer value to an arbitrary value during the count down with the use of a control msg.
- start the timer with a control msg (i.e. a msg with a control topic string).

Input

The node evaluates the following input msg types:
- Input msg with a msg.payload contents of false (boolean) or '0' (number).
This msg type stops resp. finishes the timer. The Timer Off payload is emitted also in this case.
- Input msg with a msg.topic set to "control" and a msg.payload set to an arbitrary number value. This reloads the timer with the desired msg.payload value immediately and works at a running countdown as well as a non startet or elapsed countdown timer.
- All other input msg do start/restart the timer if it is stopped.

Outputs

The node contains two outputs:
- The primary output (upper output) emits an output msg at the countdown start/stop instant of time. These msg.payload contents are configurable. If Option "Send Outputmessage on Reset" ist set, the message is send, when the timer is stopped. Otherwise, the Stop message will only by send, if the timer reaches zero.
- The secondary output (lower output) emits the remaining time every second during the timer runs. The msg.payload holds the remaining counting value

Examples

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This example shows the basic behaviour with
- starting the timer via an input msg (inject node)
- showing the behaviour of the two outputs of the node

Just activate the inject and look at the output debug node status messages.

!Alt text
basic flow
Fig. 3: Basic example flow

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This example shows how to
- handle messages at the start and the end of the countdown
- retrigger the timer during it runs

Text messages are output on the first output at start and end of the countdown.
You can restart the timer by activating the inject node during the countdown runs.

!Alt text
messages and retriggering flow
Fig. 4: Message sending and retriggering example flow

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This example shows the two options to stop the countdown timer.

!Alt text
stopping timer flow
Fig. 5: Timer stopping example flow

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This example shows the functionality of reloading the countdown value during a running timer.

!Alt text
reloading timer flow
Fig. 6: Timer reload example flow