PT100 with amp board  

RE: PT100 with amp board

@william-t14

I have been using the PT100 modification on my MK3 for about 1 1/2 years to print PEEK. Here are my modification suggestions:

Original Prusa i3 MK3 PT100 Upgrade

(file) thermistortables.h

new thermistortable –> 248

#if (THERMISTORHEATER_0 == 248) || (THERMISTORHEATER_1 == 248) || (THERMISTORHEATER_2 == 248) || (THERMISTORBED == 248) // Pt100 with 4k7 MiniRambo pullup & PT100 Amplifier

const short temptable_248[][2] PROGMEM = {

{000 * OVERSAMPLENR,    0},          

{239 * OVERSAMPLENR,    1},          

{247 * OVERSAMPLENR,   10},        

{257 * OVERSAMPLENR,   20},        

{265 * OVERSAMPLENR,   30},        

{273 * OVERSAMPLENR,   40},        

{281 * OVERSAMPLENR,   50},        

{289 * OVERSAMPLENR,   60},        

{297 * OVERSAMPLENR,   70},        

{305 * OVERSAMPLENR,   80},        

{313 * OVERSAMPLENR,   90},        

{321 * OVERSAMPLENR,  100},       

{329 * OVERSAMPLENR,  110},       

{339 * OVERSAMPLENR,  120},       

{347 * OVERSAMPLENR,  130},       

{353 * OVERSAMPLENR,  140},       

{361 * OVERSAMPLENR,  150},       

{369 * OVERSAMPLENR,  160},       

{377 * OVERSAMPLENR,  170},       

{385 * OVERSAMPLENR,  180},       

{393 * OVERSAMPLENR,  190},       

{401 * OVERSAMPLENR,  200},       

{409 * OVERSAMPLENR,  210},       

{417 * OVERSAMPLENR,  220},       

{425 * OVERSAMPLENR,  230},       

{431 * OVERSAMPLENR,  240},       

{439 * OVERSAMPLENR,  250},       

{447 * OVERSAMPLENR,  260},       

{453 * OVERSAMPLENR,  270},       

{461 * OVERSAMPLENR,  280},       

{469 * OVERSAMPLENR,  290},       

{475 * OVERSAMPLENR,  300},       

{483 * OVERSAMPLENR,  310},       

{491 * OVERSAMPLENR,  320},       

{499 * OVERSAMPLENR,  330},       

{505 * OVERSAMPLENR,  340},       

{513 * OVERSAMPLENR,  350},       

{519 * OVERSAMPLENR,  360},       

{527 * OVERSAMPLENR,  370},       

{533 * OVERSAMPLENR,  380},       

{541 * OVERSAMPLENR,  390},       

{549 * OVERSAMPLENR,  400},       

{617 * OVERSAMPLENR,  500},       

};

#endif

(file) Configuration_prusa.h

//#define E3D_PT100_EXTRUDER_WITH_AMP

#define E3D_PT100_EXTRUDER_WITH_AMP

change table from 247 to 248

Hardwarechanges:

https://www.reddit.com/r/prusa3d/comments/cnw8dt/how_to_set_up_mk3s_mmu2s_with_pt100/

RE: PT100 with amp board

@karl-herbert

Thanks a lot for all explanation. I made new wire connections and firmware modification.

It seems to work ! ! 🙂

But I have 2 questions :

- How to exceed 400°C ? Prusa seems to have temperature limitation about 400°.

-How can I slightly change the temperature values?

Thank you !

RE: PT100 with amp board

@micachilli

make changes in Configuration_prusa.h

-

// Maxtemps
#if defined(E3D_PT100_EXTRUDER_WITH_AMP) || defined(E3D_PT100_EXTRUDER_NO_AMP)
#define HEATER_0_MAXTEMP 410
#else

-

You have to adjust the temperature table experimentally. This is slightly different for each printer. If you want to do it exactly, you measure all entries and correct them (but is not absolutely necessary).

-

Which device did you use to measure the temperatures at the nozzle? (picture, description, link)?

Thanks!

RE: PT100 with amp board

@karl-herbert

Thank you for the answer.

Ok I will do that.
The device I use is a Fluke thermometer with a small accuracy probe with an error less than 1 ° C.

I performed 3 different measurements (heater, nozzle, heat-break) in order to calibrate.

😀

RE: PT100 with amp board

Posted by: @micachilli

@karl-herbert

Thank you for the answer.

Ok I will do that.
The device I use is a Fluke thermometer with a small accuracy probe with an error less than 1 ° C.

I performed 3 different measurements (heater, nozzle, heat-break) in order to calibrate.

😀

@micachilli

How did you redo the temp chart to better server your printer? Did you take an average from the heater, nozzle and heat break? I followed @karl-herbert instructions and built the firmware with his chart but I am undershooting by 10-13 degrees using a calibrated and certified thermopen MK4 reading at the heater cartridge. I did quite a bit of modification to my MK2.5s. It's currently stocked with a dragon hotend (high flow version) a higher wattage cartridge +10W from stock and of course the pt100 amp on the extruder. I'm going to have to build a custom thermistor profile for my setup as I am not sure why it is undershooting by such a large margin.

RE: PT100 with amp board

@micachilli

Thanks for the answer! What exactly is this thermometer type (infrared..)?

RE: PT100 with amp board

@karl-herbert

Hey Karl, thanks for the graph on the following pt100 thermistor. I believe my temps are more accurate after building the firmware but I am still about 7 degrees under the mark when I set it to 100C it is reporting 93C. Is there any way I can adjust the table without going through a simulation in ltspice? I am starting to research on how to build the simulated circuit but it is currently a bit over my head.

RE: PT100 with amp board

How did it work out to remove the resistor and attach the Pt-100.

Did it work out nice ?

I have not got my printer yet, I want to use Adafruit 31865, Pt-100  amplifier, but is going to start with ED3 analog amplifier.

RE: PT100 with amp board

@claes

I have equipped my MK3 with a PT100 set from E3D (PT-100 and Amplifier board) https://e3d-online.com/products/v6-pt100-upgrade-kit

After installed the hardware you only have to adjust the firmware (Thermistortable 247). The MK3 hotend I have equipped with a titanium heatbreak and nickel-plated copper heating block, also from E3D. The printing of PEEK works perfectly with it.

Ideally, the thermistortable should be calibrated and optimized with a PT100 simulator

(relatively expensive - I have rent it)

RE: PT100 with amp board

@karl-herbert

I found your very nice description how to connect E3D-Pt100 amplifier, 

Very good !!!!! Thank you.

Have you been looking how to connect "Adafruit 31865" to Einsy Rambo 1.1b ?

It would be extremely nice to use that amplifier connectad digitaly via SPI-interface direct to MK3S. This amplifier has very high resolution 15 bit ADC, very good common mode and so on .....

OK the analog Pt-100 is enough, but this 31865 is a overkill !!!  , and have several teoretical advantages.

I have ordered both "Adafruit 31865" and "E3D+Pt100" and is going to install the analog one and later start to try out the digital one.

RE: PT100 with amp board

I have bought E3D upgrade kit on 3Djake https://www.3djake.cz/e3d/upgradova-sada-v6-pt100 vith cooper block and nozle.

Instaled all parts and made modifications as karl-herbert describes.

Wired according his schematic. Modifified firmware with and without table 248.

And result? Temperatures are off by  40-50C.  Room teperature 24C is reported as 66C. 260C set on nozzle is 212C according thermal probe.

Am I missing something or shold I build completly new table?

I am going to test PT100 without amp to check if thermistor is OK.

RE: PT100 with amp board

It looks, that I have find culprit of wrong reading. One wire in connector of PT100 is badly crimped and it is causing bad contact. This small change in resistance is causing at least 30C difference.