bbq temperature and meat temperature

Moderators: grovkillen, Stuntteam, TD-er

Message
Author
megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

bbq temperature and meat temperature

#1 Post by megamarco83 » 28 Jul 2021, 16:13

hi, i would like to use espeasy with a esp8266 (nodemcu) to monitor my bbq temperature and my meat temperature.
i thought to use thermocouple type k with MAX31855 or max6675.
are both supported? what's the best choice?

i'm looking for these sensor:
https://nl.aliexpress.com/item/10050022 ... uxjUW&mp=1

this sensor with the amplifier MAX31855 or max6675 could be ok for espeasy?

thanks

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#2 Post by megamarco83 » 04 Aug 2021, 01:04

hi, it's me again.
i have at home one probe from a digital thermometer that's like this:
https://www.amazon.com/gp/product/B07L4TQC4B?pldnSite=1
i guess that's a thermistor.
how i can read temperature value from it? i thought to use ADC pin of esp8266 and create a task as "analog input" but i do not succeed on it.
what i should do ?
of course i don't know the parameter of this thermistor like resistance and coefficients to calculate the curve of it. what i can do to read from that sensor? if it's possible of course...
thanks for help me!!!

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#3 Post by TD-er » 04 Aug 2021, 12:37

You can measure its resistance at room temperature, to get some idea of its range.
Let's assume it has a 100 Ohm resistance.
If you then add an 1k resistor in series and connect that one to 3V3, you should measure roughly 330 mV over the NTC

GND --- NTC --- A0 input --- 1k --- 3V3

However, an NTC will show a lower resistance if the temperature rises, so maybe the 1k value isn't the best one to start with.
Maybe 270 Ohm is then better (still assuming 100 Ohm at 20C) so you'll put the range of the NTC voltage just below 1V at room temperature.

Most sensors used for higher temperatures use a thermocouple, which you need to measure differently as the voltage drop over a thermocouple isn't like a resistor and also the change is in mV.
For those there are several chips available, which are also supported in ESPEasy ;)

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#4 Post by megamarco83 » 04 Aug 2021, 12:57

i see that they are thermistors, and it seams that they are 100k
so i connect a 10k resistor and from A0 to GDN and this thermistors from A0 and 3v3

now i have taken some values (without the resistor, just measuring from jack connector of the probe to build the curve of the sensor)
https://www.thinksrs.com/downloads/prog ... ulator.htm
i taken some point and use 3 point to build the curve.
my range will be from 50°C to 95°C
so i set up
50°c
25°C
100°C
with connresponded resistor measured.
now i have the 3 parameters:
A = 0.2078147958 e-3
B = 2.898976250 e-4
c = -1.254043176 e-7

the Steinhart Hart equation is:
https://en.wikipedia.org/wiki/Steinhart ... t_equation
1/T = A + B ln(R) + C ln(R)^3

T is the temperature (in kelvins),
R is the resistance at T measured R (in ohms),
A B and C are the Steinhart–Hart coefficients

how i can setup the rules?

i try with:

Code: Select all

//1/T = A + B ln(R) + C ln(R)^3
// A = 0.2078147958 e-3
// B = 2.898976250 e-4
// c = -1.254043176 e-7

on sonda_termometrino#Analog do
  let,1,0.0002078147958    //A
  let,2,0.0002898976250    //B
  let,3,-0.0000001254043176 //C
  let,4,%value%
  let,4,ln(%value%)      //ln(R)
  let,5,([var#2])*([var#4])) //B*ln(R)
  let,6,(([var#4])^(3)) //ln(R)^3
  let,7,[var#6]*[var#3]  //C*ln(R)^3
  let,8,[var#1]+[var#5]+[var#7]   // total formula
  let,9,1/[var#8]  //1/T
  let,10,[var#9]-273.15  //from kelvin to celsius
//LogEntry,'ln of [%value%] = [var#4]'
//LogEntry,'kelvin [var#9] = [var#10] celsius'
endon
but it not work....

Code: Select all

12571408: EVENT: carne2#temperature=27.3
12572081: ACT : let,1,0.0002078147958
12572087: ACT : let,2,0.0002898976250
12572092: ACT : let,3,-0.0000001254043176
12572100: ACT : let,4,%value%
12572106: Calculate: Unknown token input: %value% = 0
12572112: ACT : let,4,ln(%value%)
12572116: Calculate: Unknown token input: ln(%value%) = 0
12572121: ACT : let,5,(0.000289897625)*(0))
12572123: Calculate: Parenthesis mismatch input: (0.000289897625)*(0)) = 0
12572128: ACT : let,6,((0)^(0.3333))
12572135: ACT : let,7,0*-0.00000012540432
12572142: ACT : let,8,0.0002078147958+0+0
12572149: ACT : let,9,1/0.0002078147958
12572155: ACT : let,10,4811.97691507199-273.15
Last edited by megamarco83 on 04 Aug 2021, 15:58, edited 1 time in total.

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#5 Post by TD-er » 04 Aug 2021, 13:07

First the rules part.
%value% is not correct, you need %eventvalue1%

Code: Select all

  let,4,ln(%eventvalue1%)      //ln(R)

Code: Select all

let,5,([var#2])*([var#4])) //B*ln(R)
No need for the braces and you have one too many

Code: Select all

let,5,[var#2]*[var#4] //B*ln(R)

Another thing about the value you get from the analog input.
It isn't linear proportional to the resistance.
The only way you can make it proportional to the resistance is when you use a constant current source instead of a constant voltage source.

You can create one using some linear voltage regulator like the LM317.
Image
Your formula needs to know the resistance of the sensor.

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#6 Post by megamarco83 » 04 Aug 2021, 15:14

TD-er wrote: 04 Aug 2021, 13:07 First the rules part.
%value% is not correct, you need %eventvalue1%

Code: Select all

  let,4,ln(%eventvalue1%)      //ln(R)

Code: Select all

let,5,([var#2])*([var#4])) //B*ln(R)
No need for the braces and you have one too many

Code: Select all

let,5,[var#2]*[var#4] //B*ln(R)
you are right now it's working! thanks!
now i calibrate new coefficient A B C using 10k resistor and correct my rules:

Code: Select all

//1/T = A + B*ln(R) + C*[ln(R)]^3
// A = 0.2847645884 e-3
// B = 2.245309467 e-4
// c = -59.37789855 e-7


on sonda_termometrino#Analog do
  let,1,0.002847645884    //A
  let,2,0.0002245309467    //B
  let,3,-0.000005937789855 //C
  let,4,(%eventvalue1%)
  let,5,ln([var#4])      //ln(R)
  let,6,([var#2])*([var#5]) //B*ln(R)
  let,7,(([var#5])^(3)) //ln(R)^3
  let,8,[var#7]*[var#3]  //C*ln(R)^3
  let,9,[var#1]+[var#6]+[var#8]   // total formula
  let,10,(1/[var#9])  //1/T
  let,11,(([var#10])-(273.15))  //from kelvin to celsius

LogEntry,'ln of [%eventvalue1%] = [var#4]'
LogEntry,'kelvin [var#10] = [var#11] celsius'
endon
now it works:

Code: Select all

749017: EVENT: carne1#temperature=25.7
749100: DS : Temperature: 25.4 (28-c1-4c-08-00-00-80-ee [DS18B20])
749105: Domoticz: Sensortype: 1 idx: 255 values: 25.4
749122: EVENT: carne2#temperature=25.4
750740: ACT : let,2,0.0002245309467
750745: ACT : let,3,-0.000005937789855
750751: ACT : let,4,(111.0)
750757: ACT : let,5,ln(111)
750763: ACT : let,6,(0.0002245309467)*(4.70953020131234)
750770: ACT : let,7,((4.70953020131234)^(3))
750778: ACT : let,8,104.455847935339*-0.00000593778986
750786: ACT : let,9,0.002847645884+0.00105743527461+-0.00062023687469
750794: ACT : let,10,(1/0.00328484428392)
750801: ACT : let,11,((304.428433608013)-(273.15))
750808: ACT : LogEntry,'ln of [111.0] = 111'
750809: ln of [111.0] = 111
750814: ACT : LogEntry,'kelvin 304.428433608013 = 31.278433608013 celsius'
750816: kelvin 304.428433608013 = 31.278433608013 celsius
just a question, i want to not have such as decimals, but just one. how i can do?
i see that there is the round function but it round only without decimals, i would like to have just one: XX.X°C
i also try to display the value on my oled using
[var#11]
but there are too much numbers after the dot :)
thanks!

TD-er wrote: 04 Aug 2021, 13:07 Another thing about the value you get from the analog input.
It isn't linear proportional to the resistance.
The only way you can make it proportional to the resistance is when you use a constant current source instead of a constant voltage source.

You can create one using some linear voltage regulator like the LM317.
Image
Your formula needs to know the resistance of the sensor.
sorry i miss this point, with Steinhart–Hart equation you create a "curve" polinomial to approssimate the "not-linear" responding of the NTC, that's why i used three point to build the curve and i choose 3 points inside my working range (for meat from 45°C to 95°C)
for BBQ temperature where the ragnge is high: from 110°C to 300°C i will use a thermocuple with MAX 31855 and dedicated espeasy task for thermocouple.
i do not use thermocouple for meat beacuse they have not the tip to easly inser inside the meat and because the external diameter is too big (more than 5mm)

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#7 Post by TD-er » 04 Aug 2021, 15:41

This formula does assume the typical curve of the resistance, but using a series resistor over a variable resistor also does not have a linear relation to the measured voltage.
I'm not sure the resulting correction using your formula is correct for the values between the 3 measured points.
I can't oversee out of the top of my head if this will result in a polynominal curve of the same degree as you're now trying to fit in your formula.

If you measured the resistance using a multimeter, the result will for sure be incorrect.
If you used the values measured by the ESP, the correction will probably be correct for those 3 points you used, but no idea if the rest will be correct, nor what the error will be.

To round to a number of decimals, you can do 2 things:
- Store the computed value in a dummy using taskvalueset. The nr. of decimals can be set in the dummy task
- Format the values using Floating point transformations

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#8 Post by megamarco83 » 04 Aug 2021, 15:56

TD-er wrote: 04 Aug 2021, 15:41 If you measured the resistance using a multimeter, the result will for sure be incorrect.
If you used the values measured by the ESP, the correction will probably be correct for those 3 points you used, but no idea if the rest will be correct, nor what the error will be.
no i used value displayed by Espeasy to create the 3 points.
TD-er wrote: 04 Aug 2021, 15:41 To round to a number of decimals, you can do 2 things:
- Store the computed value in a dummy using taskvalueset. The nr. of decimals can be set in the dummy task
- Format the values using Floating point transformations
sorry i'm not sure to understand the round using Floating point transformations
let,11,[var#11#D2.1] //#D2.1 to approximate to XX.X
in this case only XX.X numbers are displayed and what about for example with an input like: 134.763 will be => 34.7 ??
not understand:
Dx.y: Minimal ‘x’ digits zero filled & ‘y’ decimal fixed digits.
Dx: Minimal ‘x’ digits zero filled in front of the decimal point, no decimal digits. Same as Dx.0
D.y: Same as D0.y

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#9 Post by TD-er » 04 Aug 2021, 16:25

As described it uses "minimal" the set nr of decimals before the dot.
So with less nr. of decimals you will get leading zeroes.

For example assume the temperature to be 1.23456:

Code: Select all

[bme#T#D2.1]  // 01.2
[bme#T#D2]  // 01
[bme#T#D0.1]  // 1.2
[bme#T#D0.3]  // 1.235 (rounding)
But assigning to a variable doesn't make sense to format it, only when reading the value.

So it is better to format the variable when using it:

Code: Select all

[var#1#D0.1]

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#10 Post by megamarco83 » 04 Aug 2021, 16:40

thanks again for your support, now i have material to try test it :)
just last question for today, i'm testing what i have done right now with an oled and i suceed on display what i need.
now the question is, can i use http or mqtt to update the oled using some parameters that are coming from domoticz and some parameters that are inside espeasy?
i mean the information of temperature is inside espeasy => [var#11]
the information about setpoint is inside domoticz
can i create a call like this? :
http://192.168.0.138/control?cmd=oled,2,1,setpont=33,T=[var#11]

of course i test but it now works.

i try also using mqtt
inside control i setup domoticz mqtt control
Current Client ID: BBQ_138_138 (that it's %sysname%_%unit%)

so i try to use simple command:
mosquitto_pub -t BBQ_138_138/cmd -m oled,2,1,test

but the oled not display the word "test"
if i use
http://192.168.0.138/control?cmd=oled,2,1,test
it works

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#11 Post by TD-er » 04 Aug 2021, 21:19

Not all MQTT controllers support commands.
The OpenHAB MQTT controller does support commands, but it is rather limited for now.

Does the controller subscribe to the topic you try to send commands to?

Code: Select all

mosquitto_pub -t BBQ_138_138/cmd -m oled,2,1,test

does send to the topic "BBQ_138_138/cmd"
Since the OpenHAB MQTT controller does try to match the last sub-topic to be "cmd", your controller must have been subscribed to "BBQ_138_138/#"
Or to make it a bit more universal, "%sysname%_%unit%/#"

However, the default topic it subscribes to is: "%sysname%/#"

So I guess if you publish like this, it will probably work:

Code: Select all

mosquitto_pub -t BBQ_138/cmd -m oled,2,1,test

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#12 Post by megamarco83 » 04 Aug 2021, 22:34

thanks for your help.
right now i'm playing a bit with mqtt and yes, i had to implement a second mqtt controller inside espeasy and set it as OpenHAB MQTT

using http commands i do not succeed on my test to update oled with a variable.
is it possible do something like:
http://192.168.0.138/control?cmd=oled,2,1,setpont=33,T=[var#11]
i mean send a http command that contain a variable.

thanks

p.s i ordered also a MAX 31855 and a thermocouple type k that i will use for BBQ temperature.
i see the plugin for thermocouple inside espeasy and the calibration is mada by two points. is it linear the response of thermocouple?
thanks again

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#13 Post by TD-er » 05 Aug 2021, 01:48

Not 100% sure about the Thermocouple calibration as part of it is also done in the used chip.
I think it is linear (upto some temperature, depending on the metals used in the probe) as the thermocouple effect is fairly linear depending on temperature change.
So depending on the materials used, it may show non-linear behavior if the temperature is outside the given range of the probe.
Typical ranges are upto 850 C, so let's hope your BBQ doesn't get to that point, or else you have to scrape off quite a lot of charcoal or never be affraid of diarrhea again ;)

Not sure why the [var#1] is not working if you enter it via HTTP.
Could be that it just got messed up by the URL encoding.
You can also try %v1% as it is a short code for [var#1] without the option to format it as we discussed before (nr. of decimals)
I don't know what the # and [] will be turned into in the URL.
Also you may want to check "Tolerant last parameter" on the Tools->Advanced page as you also have a comma in your command argument.

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#14 Post by megamarco83 » 05 Aug 2021, 08:31

TD-er wrote: 05 Aug 2021, 01:48
Not sure why the [var#1] is not working if you enter it via HTTP.
Could be that it just got messed up by the URL encoding.
You can also try %v1% as it is a short code for [var#1] without the option to format it as we discussed before (nr. of decimals)
I don't know what the # and [] will be turned into in the URL.
Also you may want to check "Tolerant last parameter" on the Tools->Advanced page as you also have a comma in your command argument.
hi, thanks again for big support!
i test with and without option about tolerant last parameter with this http send from web browser chrome and also firefox:

Code: Select all

http://192.168.0.138/control?cmd=oled,2,1,T=%v1%
i received the feedback "OK" inside the web browser
but this is the log of ESP8266

Code: Select all

Log
Logging: Info (2)
182266: WD : Uptime 3 ConnectFailures 0 FreeMem 16840 WiFiStatus WL_CONNECTED 3 ESPeasy internal wifi status: Conn. IP Init
183120: HTTP: oled,2,1,T=
it seams that he not receive the %v1%

anyway much better than:

Code: Select all

http://192.168.0.138/control?cmd=oled,2,1,T=[var#1]
where inside log i can see nothing, but inside web brawser also with this command i see "OK" feedback.
do you have other ideas?

i'm try to update the script adding other 3 probes for meat to have 4 in total.
so i buy an ADS1115 to have other 3 additional ADC input.
in the mean time that i'm waiting to receive i try to think about how to manage, i create this task for the probe2:
Screenshot 2021-08-05 at 08-22-17 BBQ_138.png
Screenshot 2021-08-05 at 08-22-17 BBQ_138.png (5.94 KiB) Viewed 2818 times
Screenshot 2021-08-05 at 08-17-43 BBQ_138.png
Screenshot 2021-08-05 at 08-17-43 BBQ_138.png (54.76 KiB) Viewed 2818 times

so i think that looking at my rules for probe1 where i used 11 internal variable i will need for 4 probes => 44 variables.
there is a limitation in this ?

below the rules with adding another one.
could i make something different if 44 internal variables are not allowed?


here my rules with the second probe added:

Code: Select all

on System#Boot do
oled,2,1,ATTIVARE
oled,4,1,DomoticZ
oled,6,1,STANDY(from_rules)
endon

// -------- thermo #1 ---------------
// 1/T = A + B*ln(R) + C*[ln(R)]^3
// A = 0.2847645884 e-3
// B = 2.245309467 e-4
// c = -59.37789855 e-7

on sonda_termometrino#Analog do
  let,1,0.002847645884    //A
  let,2,0.0002245309467    //B
  let,3,-0.000005937789855 //C
  let,4,(%eventvalue1%)
  let,5,ln([var#4])      //ln(R)
  let,6,([var#2])*([var#5]) //B*ln(R)
  let,7,(([var#5])^(3)) //ln(R)^3
  let,8,[var#7]*[var#3]  //C*ln(R)^3
  let,9,[var#1]+[var#6]+[var#8]   // total formula
  let,10,(1/[var#9])  //1/T
  let,11,(([var#10])-(273.15))  //from kelvin to celsius
  let,11,[var#11#D2.1]  //#D0.1 to approximate to XX.X
LogEntry,'-------------->ln of [%eventvalue1%] = [var#4]'
LogEntry,'--------------> kelvin [var#10] = [var#11] celsius'
   if [sonda_termometrino#Analog] > 50  //check that is not disconnected  ==>>> 50 ADC value per sonda termometro4sonde
            LogEntry,'---------------------------> ADC misura = [%eventvalue1%] '
            Publish domoticz/in,'{ "idx" : 256, "nvalue" : 0, "svalue" : "[var#11]" }'
   else
            // do nothing (non aggiorno domoticz così grazie al controllo di dzvents si spegne)
   endif
endon




// -------- thermo #2 ---------------
// 1/T = A + B*ln(R) + C*[ln(R)]^3
// A = 0.2847645884 e-3
// B = 2.245309467 e-4
// c = -59.37789855 e-7

on thermosensor2#Analog do
  let,12,0.002847645884    //A
  let,13,0.0002245309467    //B
  let,14,-0.000005937789855 //C
  let,15,(%eventvalue2%)   //  => eventvalue2 it''s the value coming from task [thermosensor2#Analog]  ???
  let,16,ln([var#15])      //ln(R)
  let,17,([var#13])*([var#16]) //B*ln(R)
  let,18,(([var#16])^(3)) //ln(R)^3
  let,19,[var#18]*[var#14]  //C*ln(R)^3
  let,20,[var#12]+[var#17]+[var#19]   // total formula
  let,21,(1/[var#20])  //1/T
  let,22,(([var#21])-(273.15))  //from kelvin to celsius
  let,22,[var#22#D2.1]  //#D0.1 to approximate to XX.X
LogEntry,'-------------->ln of [%eventvalue1%] = [var#15]'
LogEntry,'--------------> kelvin [var#21] = [var#22] celsius'
   if [thermosensor2#Analog] > 50  //check that is not disconnected  ==>>> 50 ADC value per sonda termometro4sonde
            LogEntry,'---------------------------> ADC misura = [%eventvalue2%] '
 //           Publish domoticz/in,'{ "idx" : 257, "nvalue" : 0, "svalue" : "[var#22]" }'
   else
            // do nothing (non aggiorno domoticz così grazie al controllo di dzvents si spegne)
   endif
endon

i have see also another problem (of course now ADS1115 is not connect) but running the code i see:

Code: Select all

 ACT : let,16,ln(-32768.00000000000601)
358957: ACT : let,17,(0.0002245309467)*(nan)
358960: Calculate: Unknown token input: (0.0002245309467)*(nan) = 0
358964: ACT : let,18,((nan)^(3))
358966: Calculate: Unknown token input: ((nan)^(3)) = 0
358971: ACT : let,19,0*-0.00000593778986
358979: ACT : let,20,0.002847645884+0+0
358985: ACT : let,21,(1/0.002847645884)
358992: ACT : let,22,((351.167259109946)-(273.15))
i put a comment inside rules because i'm not sure that i'm taking the correct value...
let,15,(%eventvalue2%) // => eventvalue2 it''s the value coming from task [thermosensor2#Analog] ???
or %eventvalueX% where the "X" is the first number given by the task ?
example a task with DHT22 will give back: %eventvalue1% = temperature %eventvalue2% = humidity ?
so in this case i need the %eventvalue1%
a part of that i think that the error is coming because a logarithm of negative value ...


can you put me on the right way another time? :)
thanks!

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#15 Post by TD-er » 05 Aug 2021, 21:53

ln(-1) is invalid => NaN (ln of a negative value is invalid)
So the calculation is failing correct here I guess ;)

About the command you try to do, can you test it by pasting it in the command field on the tools page?
This allows you to test if it is working and also will generate an URL just how you need it including the correct HTML escaped characters.

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#16 Post by megamarco83 » 06 Aug 2021, 00:01

TD-er wrote: 05 Aug 2021, 21:53
About the command you try to do, can you test it by pasting it in the command field on the tools page?
This allows you to test if it is working and also will generate an URL just how you need it including the correct HTML escaped characters.
yes i tested, sorry to forgot to report.

Code: Select all

oled,2,1,T=[var#1]
gives the command:

Code: Select all

oled,2,1,T=0.002847645884
and oled is update accordingly

Code: Select all

oled,2,1,T=%v1%
gives the command:

Code: Select all

oled,2,1,T=0.002848
and oled is update accordingly
So both are working, but it seams that %v1% truncate the numbers....
and using http command like: http://192.168.0.138/control?cmd=oled,2,1,T=[var#1] or http://192.168.0.138/control?cmd=oled,2,1,T=%v1% (also tested with brackets "" or '' ) is not working.

2) question about ADS1115
what is it the gain?
Cattura.JPG
Cattura.JPG (19.88 KiB) Viewed 2786 times
2/3x or 1x etc...
what i should use?
my thermistor is 100k and i used 1k resistor:
3v3-----100k(thermistor)----A0----10k----GND
so if i need to use 4 probes, thanks to ADS1115 set Input Multiplexer = AIN0-gnd (for first probe) then in a second task Input Multiplexer = AIN1-gnd (for second probe) and so on....
but what about the gain to be selected?

3) using ADS1115 to implement in total 4 probes will need to use (looking at my rule that will be quadruplicated) 44 user var in total.
there is a limit on number of total user variables?

4)i'm playing also with thermocouple and i see that there is a dedicated plug-in
but there isn't the calibration here:
Screenshot 2021-08-05 at 23-32-31 BBQ_138.png
Screenshot 2021-08-05 at 23-32-31 BBQ_138.png (53.41 KiB) Viewed 2786 times
why?

5) i think that there are some "issue" on displaying options related to selected drive, i mean if i choose the RTD and type in MAX31865, no options are been showed, but it's just a matter of refresh the plug-in webpage and then the correct parameter appear (you have to submit, then quit and re-enter to make appear the thermocouple type menu)
but a part of that, i see that there are also "RTD" selection
Screenshot 2021-08-05 at 23-40-40 BBQ_138.png
Screenshot 2021-08-05 at 23-40-40 BBQ_138.png (39.16 KiB) Viewed 2786 times
i do not know what kind of thermistors are the probe of my thermometer (i suppose NTC 100k because at 25°C i measured 98,6k...but i can't be sure about type) .....so the question is: can i try to use this section of plug-in or RTD probe is working in another way and better to use the ADC plugin with the formula?
p.s. the formula is the Steinhart Hart equation typically used for thermistor that describe the curve using 3 coefficients: A, B, C
https://en.wikipedia.org/wiki/Steinhart ... t_equation

6) using familiar type = thermocouple
i see that i can choose as driver: MAX31865 or MAX6675 or MAX31866
what's the best to choose for my application in your opinion?
anyway none selection of these three allow a calibration (see my question at point 4)

big thanks for all!!!!

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#17 Post by TD-er » 06 Aug 2021, 00:04

Have you tried testing your command via the command field on the tools page?
Just tested it here and it resulted in this URL with the command:

Code: Select all

http://192.168.10.86/tools?cmd=oled%2C2%2C1%2CT%3D%5Bvar%231%5D

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#18 Post by megamarco83 » 06 Aug 2021, 00:14

TD-er wrote: 06 Aug 2021, 00:04 Have you tried testing your command via the command field on the tools page?
Just tested it here and it resulted in this URL with the command:

Code: Select all

http://192.168.10.86/tools?cmd=oled%2C2%2C1%2CT%3D%5Bvar%231%5D
how you obtained this?

Code: Select all

http://192.168.10.86/tools?cmd=oled%2C2%2C1%2CT%3D%5Bvar%231%5D
ps. tested and working but not understand how you "transofrmed"

Code: Select all

http://192.168.0.138/control?cmd=oled,2,1,T=[var#1]
in

Code: Select all

http://192.168.0.138/tools?cmd=oled%2C2%2C1%2CT%3D%5Bvar%231%5D
what do you wrote inside "-> tools -> command field" to have it?

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#19 Post by TD-er » 06 Aug 2021, 00:15

I just pressed the "submit" button and then copied the URL from the browser, just like I suggested before.

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#20 Post by megamarco83 » 06 Aug 2021, 00:23

TD-er wrote: 06 Aug 2021, 00:15 I just pressed the "submit" button and then copied the URL from the browser, just like I suggested before.
stupid me!!!
i was looking inside the field "response of command" and i do not look at web brawser that changed and displayed the command!
mmmmm sorry, i notice only now....!!!

p.s. when you have time could you please have a look at the other question of post above?
and sorry again, i spend many time to test and look at command field / response filed that i never look at http in the browser that changed... :(

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#21 Post by TD-er » 06 Aug 2021, 00:34

I haven't used these chips, so I am not sure I can answer about what those chips exactly do for all the different thermo sensors supported.
I also have to read the datasheets, or the plugin documentation: https://espeasy.readthedocs.io/en/lates ... #p039-page
Have you browsed through the docs?

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#22 Post by megamarco83 » 06 Aug 2021, 18:58

TD-er wrote: 06 Aug 2021, 00:34 I haven't used these chips, so I am not sure I can answer about what those chips exactly do for all the different thermo sensors supported.
I also have to read the datasheets, or the plugin documentation: https://espeasy.readthedocs.io/en/lates ... #p039-page
Have you browsed through the docs?
hi, yes, i read these documents, and as far as i understand the thermocouple are not linear....so that's why i'm asking about calibration.
i also read the documentation of espeasy.
unfortunately i don't yet received the thermocouple and MAX31855 to test better, so right now only theory :)

last question what about the number of variables that espeasy can mange ? do you know how many i can setup?
thanks

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#23 Post by TD-er » 06 Aug 2021, 19:05

Which variables do you mean?
Those like [var#1] in the rules?
That's limited to the amount of free memory.
A few months ago I removed the limit, which was 16.

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#24 Post by megamarco83 » 08 Aug 2021, 10:07

Yes i'm referring to var#1
So i can use 44 variables? From var#1 till var#44?
If i will move to esp32, i see that it has adc on gpio33 gpio34 gpio32 gpio35 gpio36 gpio39
In this case i can use directly these gpio instead of using ads1115 like in esp8266?

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#25 Post by TD-er » 08 Aug 2021, 14:43

Please be aware that you only use those GPIO pins connected to ADC1 on the ESP32 when measuring analog values.
ADC2 is also used by WiFi so if you combine WiFi and analog values on those GPIO pins connected to ADC2 you will get very unpredictable results.

You don't have to use sequential numbers for the variables.
You can also prefix them with some number to group them.
e.g. starting with 100 for thing A, 200 for thing B etc...
The max nr you can use is 2^32 -1, or roughly 4 billion.

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#26 Post by megamarco83 » 09 Aug 2021, 11:05

TD-er wrote: 08 Aug 2021, 14:43 Please be aware that you only use those GPIO pins connected to ADC1 on the ESP32 when measuring analog values.
ADC2 is also used by WiFi so if you combine WiFi and analog values on those GPIO pins connected to ADC2 you will get very unpredictable results.
ok, un derstand, thanks for pointed it out.
so i see that for ADC there are 5 GPIOs:
ADC1 ch0 GPIO36
ADC1 ch7 GPIO35
ADC1 ch6 GPIO34
ADC1 ch5 (t8) GPIO33
ADC1 ch4 (t9) GPIO32

what's the best?
can i use all of them to have 5 temperature probes?
TD-er wrote: 08 Aug 2021, 14:43 You don't have to use sequential numbers for the variables.
You can also prefix them with some number to group them.
e.g. starting with 100 for thing A, 200 for thing B etc...
The max nr you can use is 2^32 -1, or roughly 4 billion.
4 billion? mmmm hope that will be enough :-)

other question:
i flashed my esp32 with downloadtool using parameters as wiki show.
i used the ESP_Easy_mega_20210802_display_ESP32_4M316k-factory.bin
this is the only one that show ESP_Easy AP network...the other firmware tested never show the AP after end of flash procedure...

now i try to update with: ESP_Easy_mega_20210802_max_ESP32_16M1M.bin
(not with -factory) because i understand from wiki that on OTA update (advanced-> firmware update) i should use version without -factory, and -factory should be used only on serial flash.
but i receive this errors on OTA update:
Update error: Not Enough Space

so what i'm doing wrong?
thanks

User avatar
Ath
Normal user
Posts: 1103
Joined: 10 Jun 2018, 12:06
Location: NL

Re: bbq temperature and meat temperature

#27 Post by Ath » 09 Aug 2021, 11:14

You can't use a .bin file for a 16M(B) Flash ESP32 onto a 4MB ESP32, the allocated size for OTA download is about 1800kB, where the 16M build .bin files are ~2250kB.

For flashing via serial you must use the -factory.bin file, starting at address 0, with no other extra files, when updating via OTA, use the .bin file without 'factory' in the name, as explained on the RTD docs: https://espeasy.readthedocs.io/en/lates ... shing.html
/Ton

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#28 Post by TD-er » 09 Aug 2021, 11:20

The 16M version is meant for units with 16MByte of flash, which is not very common at this moment.
So I guess you should probably use a version with "4M" in the name.

Also you mention wiki, but I assume you mean the Read The Docs?
It also has a page on what GPIO best to use: https://espeasy.readthedocs.io/en/lates ... e-on-esp32

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#29 Post by megamarco83 » 09 Aug 2021, 12:55

TD-er wrote: 09 Aug 2021, 11:20 The 16M version is meant for units with 16MByte of flash, which is not very common at this moment.
So I guess you should probably use a version with "4M" in the name.
well noted, thanks.
i see that there aren't available bin file version for max (all plugins) with 4mb....
TD-er wrote: 09 Aug 2021, 11:20 Also you mention wiki, but I assume you mean the Read The Docs?
It also has a page on what GPIO best to use: https://espeasy.readthedocs.io/en/lates ... e-on-esp32
very good, thanks
i see that for these GPIO with ADC ch1 (that i post above) there aren't specific comments, so i can use all of them, correct?

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#30 Post by TD-er » 09 Aug 2021, 13:32

I suggest you start with the pins from 34 and up, as those are "input-only" pins, so they are less usable for other purposes.

There is indeed no "max" build for 4M units, as it simply won't fit.

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#31 Post by megamarco83 » 09 Aug 2021, 22:44

i'm testing ESP32
it seams that i need to calibrate again the NTC because the values of ADC that i receive are very different.
i'm using same configuration:
my thermistor is 100k and i used 10k resistor:
3v3-----100k(thermistor)----A0----10k----GND

with esp8266 at 25°C i received 100 (looking at espeasy numbers of ADC)
now with esp32 i receive ADC value around 240 (connected at gpio34)

with esp8266 the values was very stable, now with esp32 i set interval=4 seconds, and if i do not touch the NTC and i look for 5 shot values i see: 252, 245, 232, 246, 240.
so very different values...why?
there is a way to ask for a 5 measures every 1 second and then make an average of these 5 values?


last question. if i use one ESP8266 and then for some reason i need to substitute it, i will have to calibrate again the probe on the new esp8266 ?
same answer i think that will be applicable also for ESP32,....
thanks!

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#32 Post by TD-er » 09 Aug 2021, 22:56

The ADC of ESP32 does have a higher resolution.
It is 10 bit (ESP8266) vs. 12 bit (ESP32)

So where the ESP8266 may fluctuate +/- 1 digit, the same noise would be +/- 4 digits on the ESP32.

The calibration should be done on any unit, regardless if it is ESP8266 or ESP32, as the tolerances of the resistors is probably affecting the measurements.
Apart from that the ESP32 does have a non-linear behavior, which is kind of flat around 0.

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#33 Post by megamarco83 » 09 Aug 2021, 23:10

so for you is it better (for my application) using esp8266 + ADS1115 or ESP32 ?
i would like to have 3 or 4 ADC input to menage 3/4 NTC probes.

looking at ADS1115 i see this:
ADS1115_gain.JPG
ADS1115_gain.JPG (31.82 KiB) Viewed 2537 times
what is "gain" supposed to do?

last...unfortunately i ordered (my mistake) one ADS1105 and not ADS1115, i guess that i can't use ADS1105 with espeasy, right?
thanks!

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#34 Post by TD-er » 09 Aug 2021, 23:34

The gain is an internal amplifier inside the ADC chip.
As you can see by the Full Scale (=FS) range alongside the gain, the higher the gain, the lower the full scale range is.
So at 1x gain (= no amplification) the sensor will output its max value at 4.096 V.

The gain is a trade-off between resolution and noise, as any amplification will also amplify the noise.
Given you plan on interpolating the signal, I guess you need to go with the highest resolution.
So if you know your max voltage, I would base the set gain on that so that you're as close as possible to the mentioned FS voltage with your max. input voltage.

I don't know what the differences are between the ADS1115 and ADS1105. As far as I can see, the ADS1105 is not mentioned in the source code as being compatible, so I guess you cannot use it with the plugin for ADS1115.
You can try and see how it behaves.
It might be the expected gain differs, the max count of the ADC is different, etc. These would result in a reported value which is off by some factor, but can still be used.
If it really is a different chip, then it can't be used with this plugin.

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#35 Post by TD-er » 09 Aug 2021, 23:37

Hmm there appears to be an ADS1015, not the ADS1105.
The ADS1015 should be supported by the Playground plugin P167, but I have no idea how well that one might compile against the current ESPEasy source code.

User avatar
Ath
Normal user
Posts: 1103
Joined: 10 Jun 2018, 12:06
Location: NL

Re: bbq temperature and meat temperature

#36 Post by Ath » 10 Aug 2021, 12:07

The ADS1015 is a 'less accurate' brother of the ADS1115, where the ADS1115 uses 16 bit resolution, the ADS1015 only has 12 bit resolution. For the rest they seem to be compatible.

Largest difference between the current P025 ADS1115 plugin and the Playground P167 ADS1015 is that the latter supports all 4 analog inputs, where the P025 only seems to support the first input 'AIN0' as 'Analog'. That could be a small project, to add multiple input support to that plugin (too) 8-) (I have such board available in my hardware-inbox).
/Ton

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#37 Post by megamarco83 » 10 Aug 2021, 13:30

Ath wrote: 10 Aug 2021, 12:07 The ADS1015 is a 'less accurate' brother of the ADS1115, where the ADS1115 uses 16 bit resolution, the ADS1015 only has 12 bit resolution. For the rest they seem to be compatible.

Largest difference between the current P025 ADS1115 plugin and the Playground P167 ADS1015 is that the latter supports all 4 analog inputs, where the P025 only seems to support the first input 'AIN0' as 'Analog'. That could be a small project, to add multiple input support to that plugin (too) 8-) (I have such board available in my hardware-inbox).
can you please help me on using both:
P025 ADS1115 plugin => to use all 4 analog inputs ( i bought a new one, hope it will arrive in 2wekks...)
P167 ADS1015 plugin => to compile on ESP8266_4MB1MB.bin i do not succeed on compile it on arduino IDE
thanks

User avatar
Ath
Normal user
Posts: 1103
Joined: 10 Jun 2018, 12:06
Location: NL

Re: bbq temperature and meat temperature

#38 Post by Ath » 10 Aug 2021, 14:27

P025 has a quite complex combination setup of either single-ended input (against GND) or a differential input (between AIN0/AIN1, AIN0/AIN3, AIN1/AIN3 or AIN2/AIN3), and though the plugin can be changed to handle all 4 inputs simultaneously, for now I choose to not try to change that setup, as I don't see much to be gained from, at the moment (IOW: It's more work than I originally estimated :shock:).
You can use all AIN0..AIN3 ports by configuring multiple ADS1115's with different "Input Multiplexer" settings (they can live side by side in ESPEasy).

P167 I haven't really looked at, but the code is somewhat outdated. I suggest to first try the ADS1015 with the ADS1115 plugin, and if that doesn't work (at all), I may try to port the plugin from the Playground.
/Ton

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#39 Post by megamarco83 » 10 Aug 2021, 15:09

Ath wrote: 10 Aug 2021, 14:27 P025 has a quite complex combination setup of either single-ended input (against GND) or a differential input (between AIN0/AIN1, AIN0/AIN3, AIN1/AIN3 or AIN2/AIN3), and though the plugin can be changed to handle all 4 inputs simultaneously, for now I choose to not try to change that setup, as I don't see much to be gained from, at the moment (IOW: It's more work than I originally estimated :shock:).
You can use all AIN0..AIN3 ports by configuring multiple ADS1115's with different "Input Multiplexer" settings (they can live side by side in ESPEasy).
just let me understand.
if i need 4 ADC input you mean:
1) create 4 tasks with
- task1 = AIN0 to GND = for brobe1
task2 = AIN1 to GND = for brobe2
task3 = AIN2 to GND = for brobe3
task4 = AIN3 to GND = for brobe4
with this configuration plugin P025 should work for my scope? it's correct?
Ath wrote: 10 Aug 2021, 14:27 P167 I haven't really looked at, but the code is somewhat outdated. I suggest to first try the ADS1015 with the ADS1115 plugin, and if that doesn't work (at all), I may try to port the plugin from the Playground.
ok thanks for your feedbak, i will get a try using ADS1015 with the ADS1115 plugin by end of August, tomorrow i'll be far from home for holidays.
i will let you know when i'll be back.
anyway i will test ADS1015 using ADS1115 plugin configurated like written by me above, right?

User avatar
Ath
Normal user
Posts: 1103
Joined: 10 Jun 2018, 12:06
Location: NL

Re: bbq temperature and meat temperature

#40 Post by Ath » 10 Aug 2021, 15:32

Yes, that's the idea :D

Have a nice holiday!
/Ton

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#41 Post by megamarco83 » 22 Aug 2021, 18:39

Ath wrote: 10 Aug 2021, 15:32 Yes, that's the idea :D

Have a nice holiday!
hi, i'm back :)
i received my MAX31855 and i connect it to may esp32 and set the connections:
max - Esp32
sck - gpio18
cs - gpio21
so - gpio19
gnd -gnd
vcc - 3v3

but i receive strange negative values...that continue to change...
here the log with sensor on my desk:

Code: Select all

305382: P039 : termoc : Temperature: -27.2
305388: Domoticz: Sensortype: 1 idx: 263 values: -27.2
305412: EVENT: termoc#Temperature=-27.2
306822: ADC : Analog value: 220 = 220.5 (22 samples)
306834: EVENT: thermosensor2#Analog=220.5

309173: P039 : termoc : Temperature: -27.5

309495: EVENT: termoc#Temperature=-27.5

313593: P039 : termoc : Temperature: -25.5
313597: Domoticz: Sensortype: 1 idx: 263 values: -25.5
313627: EVENT: carne2#temperature=25.1
313823: EVENT: termoc#Temperature=-25.5

321370: P039 : termoc : Temperature: -28.7
321375: Domoticz: Sensortype: 1 idx: 263 values: -28.7
321399: EVENT: carne2#temperature=25.1
321535: EVENT: termoc#Temperature=-28.7

325189: EVENT: carne1#temperature=25.3
325336: P039 : termoc : Temperature: -27.0
325341: Domoticz: Sensortype: 1 idx: 263 values: -27.0
325359: EVENT: carne2#temperature=25.1
325500: EVENT: termoc#Temperature=-27.0

329407: P039 : termoc : Temperature: -28.7
329412: Domoticz: Sensortype: 1 idx: 263 values: -28.7
329436: EVENT: carne2#temperature=25.1
329564: EVENT: termoc#Temperature=-28.7


333337: P039 : termoc : Temperature: -29.0
333342: Domoticz: Sensortype: 1 idx: 263 values: -29.0
333359: EVENT: carne2#temperature=25.1
333494: EVENT: termoc#Temperature=-29.0

337337: P039 : termoc : Temperature: -27.5
337342: Domoticz: Sensortype: 1 idx: 263 values: -27.5

337502: EVENT: termoc#Temperature=-23.5
they are also very different and not homogeneous ....the sensor is on my desk without deviations of temperatures

if i touch it with my hands i see values from -46°C to -50°C
1.JPG
1.JPG (53.66 KiB) Viewed 1729 times

my thermocouple is type "K" but i do not see the possibility on set it if i select MAX31855
if i select MAX31856 i can choose the type of thermocuple, (i tried it but not work, but ok, my sensor is MAX31855 )
2.JPG
2.JPG (91.48 KiB) Viewed 1729 times

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#42 Post by TD-er » 22 Aug 2021, 19:07

A thermocouple generates a voltage when 2 different metals are connected to each other. This voltage depends on the temperature.
So maybe you have to switch the 2 contacts of the probe?

Otherwise it is a really bad day for a BBQ at minus 20-ish degree ;)

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#43 Post by megamarco83 » 22 Aug 2021, 21:27

TD-er wrote: 22 Aug 2021, 19:07 A thermocouple generates a voltage when 2 different metals are connected to each other. This voltage depends on the temperature.
So maybe you have to switch the 2 contacts of the probe?
i thought that and i also tried it (just switch T+ and T-) ...but nothing better, i see positive values at this time but from +6°C to +12°C (without any real deviation on temperature, so wrong value and inside a "high" range)
i also tried with another thermocouple type K that i have, at this time espeasy show values from +14°C to +21°C (not possible because i have +26°C in my house right now and DS18B20 connected to same esp32 and placed in same desk show +25.6°C)
but also in this case to have positive value i had to switch T+ and T-

i find also a MAX6675 using this one i see correct values (and without switching T+ and T-) => T+=red T-=blue so i used correct connection with both my sensors (both are thermocouple type k)

https://it.aliexpress.com/item/10050026 ... 4c4dPRa2g4
this is my device and one of my probe ( i have the smallest one "rectangular") the other probe is still type k
TD-er wrote: 22 Aug 2021, 19:07 Otherwise it is a really bad day for a BBQ at minus 20-ish degree ;)
yes! :D :D :D :D

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#44 Post by TD-er » 23 Aug 2021, 00:17

Do you have a multimeter which supports measuring temperature using a probe?
Can you try to see what happens if you connect this probe you're now trying to use with your multimeter?
Make sure to also test with different temperatures (e.g. holding in your hand, put it against something cold, etc)
All multimeters that support temperature probes also have some internal temperature sensor, so if you short the inputs of the multimeter in temperature mode, you will still read the internal temp sensor of the multimeter. Therefore you need to test to see if you can measure any change in temperature on the probe.

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#45 Post by megamarco83 » 23 Aug 2021, 14:15

TD-er wrote: 23 Aug 2021, 00:17 Do you have a multimeter which supports measuring temperature using a probe?
Can you try to see what happens if you connect this probe you're now trying to use with your multimeter?
unfortunately i don't have a multimeter with temperature support... :(
so i can't make this test.
TD-er wrote: 23 Aug 2021, 00:17 Make sure to also test with different temperatures (e.g. holding in your hand, put it against something cold, etc)
All multimeters that support temperature probes also have some internal temperature sensor, so if you short the inputs of the multimeter in temperature mode, you will still read the internal temp sensor of the multimeter. Therefore you need to test to see if you can measure any change in temperature on the probe.
but sorry, i have two probes: both thermocouple type k and one MAX31855 (not working with both probes: negative or strange values dispayed) and one MAX6675 tested with both probles and with results that seams in line with DS18B20.
the connection for MAX31855 are the same of MAX6675.
and i see that selecting both integrates there is not the possibility to select what kind of thermocouple is in place (type J, tipe K etc...) both of mine are type K, but again with MAX6675 seams to be ok.

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#46 Post by TD-er » 23 Aug 2021, 15:47

OK, so the probes seem to work fine.
Could be the chip of the MAX31855 is damaged, or the implementation needs a patch to work properly with these probes.

I have no experience with them myself.

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#47 Post by megamarco83 » 23 Aug 2021, 16:33

TD-er wrote: 23 Aug 2021, 15:47 OK, so the probes seem to work fine.
yes it seams so...
TD-er wrote: 23 Aug 2021, 15:47 Could be the chip of the MAX31855 is damaged, or the implementation needs a patch to work properly with these probes.
I have no experience with them myself.
mmm damaged chip could be but it's new, and seams to be strange that it not works...but ok there is also this possibility of course.
Unfortunately i don't have a replace to test it.
but looking at wiki (if i'm not wrong) should be present the possibility to choose the type of thermocouple but if i select MAX31855 or MAX6675 nothing appear to be selected as type of probe...

just a question related to ADC (do you remember the discussion that we had about NTC probe that i have and the idea to use ESP32 to monitor 4 different NTC)...
now i'm on a development board with dupont cable, if i'll move to a more definitive pcb and so also changing lenght of dupont wire, i'll need to recalibrate the values that i will see due to changing of wire lenght?

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#48 Post by TD-er » 23 Aug 2021, 16:42

Well depends on the value of the NTC I guess.
If the resistance of the NTC in the temperature range you use is low, then the additional resistance of the cabling may play a role.
But if the NTC is in the order of kOhm, then I guess it will be playing much less of a role. Error due to cabling is probably less than the measurement resolution of the ADC.

On the other hand, the difference between ESP boards may play a bigger role.

megamarco83
Normal user
Posts: 208
Joined: 13 Apr 2017, 23:09

Re: bbq temperature and meat temperature

#49 Post by megamarco83 » 23 Aug 2021, 16:54

mmm understand.
i used NTC 100k and i add a resistance of 10k to GND like this:
3v3-----100k(thermistor)----A0----10k----GND
in this case i see that using ESP32 around 110°C i see an ADC valure around 2400 that should be very close to the max of ADC....
if i would like to measure from 25°C to 250°C i should change the value of my add resistance of 10k ? what value i should use?
and....if i decide to increase the range from actually 110°C to 250°C i will have a less precice measurements inside a short range like 35-80°C (that's the meat range)
bbq range is from 80°C to 250°C
thanks!
Last edited by megamarco83 on 23 Aug 2021, 21:11, edited 1 time in total.

TD-er
Core team member
Posts: 5417
Joined: 01 Sep 2017, 22:13
Location: the Netherlands
Contact:

Re: bbq temperature and meat temperature

#50 Post by TD-er » 23 Aug 2021, 17:00

You have to get more to the middle of the ADC range as the ESP32 ADC is a bit unusable at the edges of the measurement range.
See: https://randomnerdtutorials.com/esp32-a ... duino-ide/

Image

Post Reply

Who is online

Users browsing this forum: No registered users and 29 guests