Output of the ds18b20 sensors

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Hey Folks!

can I adjust the output of the sensors so that gets 1/2 degree steps like 20,5° or 21° and not 20,45° or 19.11° ?

Many Thanks for your help!
Skarhand

PS: Here is my actually config:

{
“id”: “temperatur-sensor1”,
“name”: “Aussentemperatur Garten”,
“class”: “DS18B20Sensor”,
“hardwareId”: “28-0000066fae4c”,
“interval”: 10000
},
{
“id”: “temperatur-sensor2”,
“name”: “Wassertemperatur Gartenteich”,
“class”: “DS18B20Sensor”,
“hardwareId”: “28-0000066fa91a”,
“interval”: 10000
},
{
“id”: “temperatur-sensor3”,
“name”: “Wassertemp. Pool Vorlauf”,
“class”: “DS18B20Sensor”,
“hardwareId”: “28-03146c8e43ff”,
“interval”: 10000
},
{
“id”: “temperatur-sensor4”,
“name”: “Wassertemp. Pool Ruecklauf”,
“class”: “DS18B20Sensor”,
“hardwareId”: “28-02150024beff”,
“interval”: 10000
},

Hi @skarhand,
maybe you could combine formatNumber(variable, decimals, unit) and VariablesDevice.

I have in mind that I did this somewhere. Let me check and get back to you. But maybe above two keywords are leading you to the right path already.

EDIT:
@skarhand: Finally found it. What I did back then was, that I created a new device for it. Don’t know if there is a more elegant solution. But this works:

    {
      "id": "variable_device",
      "name": "MyVariableDevice",
      "class": "VariablesDevice",
      "variables": [
        {
          "name": "myVariable",
          "expression": "round($temperatur-sensor1.temperature,1)",
          "type": "number",
          "unit": "°C"
        }
      ]
    },

Explanation:
You are creating a new device (VariablesDevice) with the above code. As an expression you use the round() function, fill in your temperature variable created by DS18B20Sensor and the decimals. Add the new device to the mobile-frontend and there you go.

Output looks as follows:

Hey Fletcher!

That’ nice, and it works. But… ( )

Is there a way, i can round the output in half degree steps like 19,0°C or 19,5°C ?

Now with your solution I have an output in tenth degree increments like 19,1°C 19,2°C etc…

MFG
Skarhand

I think this is not possible “out of the box”. Or let’s say not that I know of. This is up to some @Developer .

@skarhand: With pimatic 0.8.78 it has now become possible. Instead of round() you can now use roundToNearest(number, steps).

So in your case:
roundToNearest($temperatur-sensor1.temperature, 0.5)

Explanation:

roundToNearest(number,steps) rounds a number or decimal to the nearest multiple

Examples:
roundToNearest(22.75, 0.5) -> 23
roundToNearest(22.74, 0.5) -> 22.5

roundToNearest(302.5, 5) -> 305
roundToNearest(302.4, 5) -> 300

best,
fletcher

And you can always change the resolution of the ds18b20

the resolution of the
DS18B20 is configurable (9, 10, 11, or 12 bits), with 12-bit readings the factory default state. This
equates to a temperature resolution of 0.5°C, 0.25°C, 0.125°C, or 0.0625°C

Resolution 9 gives 0.5

@incmve: Hi there, where do I have to put the parameter for the resolution?

@fletcher

“expression”: “roundToNearest($temperatur-sensor1.temperature, 0.5)”,

@fletcher Hello!

I think, something is wrong with the “roundToNearest” Feature. Or I’m too stupid

Here is my config:

{
  "id": "temperatursensor1",
  "name": "Flur",
  "class": "DS18B20Sensor",
  "hardwareId": "28-00000670474f",
  "interval": 10000,
},
{
  "id": "variable_device_temp1",
  "name": "Temperatur Flur",
  "class": "VariablesDevice",
  "variables": [
    {
      "name": "myVariable",
      "expression": "roundToNearest($temperatursensor1.temperature, 0.5)",
      "type": "number",
      "unit": "°C"
    }
  ]
},

But when I start Pimatic, I become the following Error:

16:20:02.557 [pimatic] Could not get attribute value of Temperatur Flur.myVariable: device is not defined

and:

Unhandled rejection ReferenceError: device is not defined
at Object._attributesMeta.(anonymous function).update (/home/pi/pimatic-app/node_modules/pimatic/lib/devices.coffee:77:64)
at VariablesDevice.<anonymous> (/home/pi/pimatic-app/node_modules/pimatic/lib/devices.coffee:87:60)
at VariablesDevice.EventEmitter.emit (events.js:117:20)
at evaluate (/home/pi/pimatic-app/node_modules/pimatic/lib/devices.coffee:649:18)
at tryCatcher (/home/pi/pimatic-app/node_modules/pimatic/node_modules/bluebird/js/main/util.js:24:31)
at Promise._settlePromiseFromHandler (/home/pi/pimatic-app/node_modules/pimatic/node_modules/bluebird/js/main/promise.js:466:31)
at Promise._settlePromiseAt (/home/pi/pimatic-app/node_modules/pimatic/node_modules/bluebird/js/main/promise.js:545:18)
at Async._drainQueue (/home/pi/pimatic-app/node_modules/pimatic/node_modules/bluebird/js/main/async.js:84:12)
at Async._drainQueues (/home/pi/pimatic-app/node_modules/pimatic/node_modules/bluebird/js/main/async.js:89:10)
at Async.drainQueues (/home/pi/pimatic-app/node_modules/pimatic/node_modules/bluebird/js/main/async.js:14:14)
at process._tickCallback (node.js:415:13)

My Pimatic Version is 0.8.81.
Can you see a bug in my config?

Thanks
Sebastian

@skarhand said:

I think, something is wrong with the “roundToNearest” Feature.

You are right. The roundToNearest implementation is buggy. I’ll file a suggested fix and keep you posted.

EDIT: Created PR https://github.com/pimatic/pimatic/pull/714

@mwittig Hey. thanks! With the fix, it works fine.

MFG
Sebastian

@skarhand That’s great.

Meanwhile sweetpi has created a new pimatic release 0.8.82 which contains the fix!

Hi,

I have 2 dht22 and 2 ds18b20 sensor on a breadboard with a nano clone running.
For the value of the first ds18b20 I have made a variable with roundToNearest. This works.
But for the second ds18b20 the standard-variable is rounded on .5 without doing anything.

{
      "id": "DS18B20",
      "name": "ds18b20",
      "class": "DS18B20Sensor",
      "hardwareId": "28-000007326c36",
      "interval": 60000
    },
    {
      "id": "DS18B20-1",
      "name": "ds18b20-1",
      "class": "DS18B20Sensor",
      "hardwareId": "28-031561f56bff",
      "interval": 60000
    },

How does it work?

@hansmerkel said:

I have made a variable with roundToNearest

Can you please post your config of the VariablesDevice? Did you try to increase the temperature reading of the second sensor, e.g. by touching the sensor with your fingers?

      "id": "rounded",
      "name": "DS18 Gerundet",
      "class": "VariablesDevice",
      "variables": [
        {
          "name": "rounded-ds18b20",
          "expression": "roundToNearest($DS18B20.temperature, 0.5)",
          "type": "number"
        }
      ]
    }
  ],

This is the first which is correct, the second one had only 0.25 instead of 0.5.
I´ve tested it also with 0.5 for both. No changes.