PT1000 with Repetier 1.04 with Rumba 8 bit

Alex

Hello
I try to make work together PT1000 with Repetier 1.04 with Rumba 8 bit
In web configurator tools I selected User Defined Table 0
I am using a custom table for Resistance and ADC values, calculated for a 4.7k Ohm generated by AI
I have tried several versions of the table: with full ADC resolution, with one decimal place, and with 10°C steps.
However, I am facing an issue: everything works fine below 100°C, but as soon as the temperature reaches 100°C, the firmware hangs.

Here is table I used

"userTable0": {
"r1": 0,
"r2": 4700,
"temps": [
{
"t": 0,
"r": 1000.000000,
"adc": 179.641
},
{
"t": 25,
"r": 1097.300000,
"adc": 193.425
},
{
"t": 50,
"r": 1193.985000,
"adc": 207.676
},
{
"t": 100,
"r": 1385.000000,
"adc": 230.654
},
{
"t": 150,
"r": 1573.465000,
"adc": 249.921
},
{
"t": 200,
"r": 1759.050000,
"adc": 266.666
},
{
"t": 250,
"r": 1941.765000,
"adc": 281.952
},
{
"t": 300,
"r": 2121.600000,
"adc": 296.742
},
{
"t": 360,
"r": 5000.000000,
"adc": 1023.000
}
],
"numEntries": 9
}

Hope for help
Thank you in advance.

Repetier

You know that the default solution for PT1000 is using MAX31865 based amplifier boards? Assuming map is correct it would map 200-250 deg C to adc values 281-266=15 so only jumps of 3 or more degree can besesolved. That will not result in stable temperatures and when you also assume adc beeing not exact that will not work. The 4.7K resistor is for normal thermistors with 100K resistence around 25 degree. This spreads temperature range very good to adc range 0-1023 so you get a useable resolution for printing temperatures.

Apart from this the table looks good, rising order. Maybe add a low range for adc 0 as well as you did for high side so allow mapping all measured adc values. But as said, you should use a special board that maps it to linear 0-5v and connect it to a pure adc input not one with 4.7k resistor. If I remember right this is what MAX31865 did. Or does it use digital communication. See documentation for this. It's years ago I wrote that stuff, not 100% sure.

Alex

I have MAX31865 as well. I used MAX31855 with hardware SPI

AI suggested to me connect it to ISP1 in this way

         pins

VIN +5V 2
GND GND 6
CLK SCK 3
SDO MISO 1
CS RESET 5
SDI MOSI 4

but it doesn't works.
Tell me pls correct way and what exactly to write in configuration.h

Alex

perhaps it's better to connect to EXT3?

I use some pins for 3d touch but 7 9 10 11 12 are free, +5 & GND too.

Repetier

Use software SPI version for the max chip and 4 unused pins. Pins 11-14 on exp3 should do. Just watch out with MISO/MOSI - rumba is master, so on MISO you put data output of chip.