Sparing lights Node Red challenge

1

Brainstorming for Node Red experts…
Here is the context, I have four lights (hue or tradfri doesn’t matter) on a candelar, name them Cand1, Cand2, Cand3 and Cand4.
At night, before dark night (nadir) if there is no motion in the room I would like only one of these lights to be lit at 30%.
At real night (during nadir) I want all lights off.
I know how to do that with Cand1 but how can I lit them in turn so that it’s not always the same which is the night light ?
Even if I don’t know how to code it I thought of a function according month day :
LightNumber= mod(Day;4)+1

What I don’t know is how to code this in Node Red to build the light name by concatenation or even if it is possible to make an entity name from a variable.

Thanks to those who take a minute to help

Regards

2

You can use the function node and then use that to pass into a call service node. This is how I do it for virtually all my lighting nodes:

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In the function node, I would do something like this (I’m doing this off the top of my head, so I’m pretty sure there is a better way). Have the function node wired into a blank call service node and it should work.

//Clear the current msg.payload
msg.payload = {};

//If counter hasn't been set in the flow context, set counter to 1.
var counter = flow.get("counter") === null ? 1 : flow.get("counter");
var entity = 'Cand' + counter;

//Increment the counter in the flow context 
flow.set("counter", counter++);

//Create the payload
msg.payload = {
    domain: 'light',
    service: 'turn_on',
    data: {
        entity_id: entity,
        brightness_pct: 30
    }
}

return msg;
3

Thanks a lot very elegant solution, I ended with a solution where the light number is according to the date of the month. I’ll use the same when time comes to turn off.

var today = new Date();
var today_day = today.getDate();
var lightnum = 0;
lightnum = (today_day % 4) +1;
var lightname = 'light.salleam' + lightnum;

msg.payload = {
    domain: 'light',
    service: 'turn_on',
    data: {
        entity_id: lightname,
        brightness_pct: 30
    }
}

return msg;
1 Like
4

I perfected a bit my function for a chandelier dealing both with the lights to turn on and the ones to turn off, made it easily adaptable for a bigger chandelier :

// Sparing chandelier lights one per day
// the function finds today’s light which should be on
// and builds an array with on and off lights
// all chandelier lights are supposed to be named in sequence (chand1, chand2,…)
var newmsg = {};
var lgt_basename = ‘light.salleam’; //what is your chandelier lights name without the number
var lgt_many = 4; // how many lights on the chandelier
var today = new Date();
var today_day = today.getDate();
var lightnum = 0;
var m_out = [];
lightnum = (today_day % lgt_many) + 1;
var lighton = lgt_basename + lightnum;

for (var i = 1; i <= lgt_many; i++) {
  if (i != lightnum) {
    newmsg = {};
    newmsg.payload = {
      domain: ‘light’,
      service: ‘turn_off’,
      data: {
        entity_id: lgt_basename + i,
      }
    }
    m_out.push(newmsg);
  } else {
    newmsg = {};
    newmsg.payload = {
      domain: ‘light’,
      service: ‘turn_on’,
      data: {
        entity_id: lighton,
        brightness_pct: 30
      }
    }
    m_out.push(newmsg);

    Copy to clipboard
  }
}
return m_out;

A big thank you to @code-in-progress for pointing me in the right direction.

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1 Like
5

This may or may not be more readable to you. It also preserves your original message object and you only need 1 output on the function node.

// Sparing chandelier lights one per day
// the function finds today's light which should be on
// and builds an array with on and off lights
// all chandelier lights are supposed to be named in sequence (chand1, chand2,…)
const lgt_basename = 'light.salleam'; // what is your chandelier lights name without the number
const lgt_many = 4; // how many lights on the chandelier
const today = new Date();
const today_day = today.getDate();
const lightnum = (today_day % lgt_many) + 1;

msg.payload = {
    domain: 'light',
    service: 'turn_off'
};

const messages = Array.from({ length: lgt_many }, () => Object.assign({}, msg));

messages[lightnum].payload = {
    domain: 'light',
    service: 'turn_on',
    data: {
        entity_id: `${lgt_basename}${lightnum}`,
        brightness_pct: 30
    }
};

return [messages];
6

This one is a bit cryptic for me :slight_smile:

I’ll study it as I’m a beginner on Javascript.

Thanks you very much

7

It’s just creating an array with the length of lgt_many and then filling it with Object.assign({}, msg) which is just doing a shallow copy of the msg object to get rid of the object reference.

So basically creating a 4 element array with each index equal to the msg object.

8

OK But how do you fill it with the lights to be off numbers ?

Ho, you use the index as light number, is that it ?

9

that’s the the second argument of Array.from is doing fill the whole array with the same thing.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/from#Using_arrow_functions_and_Array.from