MAX6675 + RAMPS 1.4

Hi everyone,

I've spent 2 days searching for some info on the web about how to get working the Thermocouple Amplifier Module MAX6675 onto RAMPS 1.4. Never found anything about it, just troubleshooting that ends on nothing clear.

So i put my hands on firmware (Repetier Firmware 0.92), using web config tool and later working directly on files generated, the only thing i got was to read the j-block temp at the time of connection to Repetier Host.

I kept looking for something, but now, instead on repetier firmware, with other firmwares available, and i did found someone who claimed to get worknig it on Marlin. So i did a lookup for the latest Marlin that i knew was updated (Erik van der Zalm) and saw that he moved out to another Git [github.com]

Downloaded RC1 version and updated my parameters (here are some of them)

// It's very iportant to leave this at "zero", it gave me some headaches
#define SERIAL_PORT 0

#ifndef MOTHERBOARD
  #define MOTHERBOARD BOARD_RAMPS_13_EFB
#endif

#define TEMP_SENSOR_0 -2

// As i have the E3Dv6 All-Metal max temp before PTFE fails is 310ºC
#define HEATER_0_MAXTEMP 310

On this Marlin version, collaborators had split motherboards pinout files, so it's easier to find out yours.
On line 245 from pins_RAMPS_13.h, as i don't have SDRamps, i changed first pin 66 to 53

// SPI for Max6675 Thermocouple
#if DISABLED(SDSUPPORT)
  #define MAX6675_SS       53 // Do not use pin 53 if there is even the remote possibility of using Display/SD card
#else
  #define MAX6675_SS       66 // Do not use pin 49 as this is tied to the switch inside the SD card socket to detect if there is an SD card present
#endif

The rest, regular modifications as needed for each machine. Whit this done, it works perfectly

P.S.: Very important thing after writing firmware to the Arduino, run M303 several times to get a nice PID tuning

This is probably no longer of interest for you, but maybe for future readers: I bought a cheap MAX6675 module + thermocouple from Ebay last Spring and I got it immediately working on RAMPS1.4 + Marlin firmware by following this tutorial.

I just found out that the Smoothieboard doesn't really work with multiple thermocouples - at least of now.

Nice - so basically the MAX6675 is supported by 1.1 RC. Could you show me how you wired it up?

For dual MAX6675's I think I have to wire everything up in parallel except the CS and that can be any pin, correct?

Hey 3DTOPO, out there is a board that supports multiple thermocouples without additional hardware, don't remember the name right now.

Yes, MAX6675 & MAX31855 are supported by default on Marlin 1.1 RC1.

MAX6675 ||       RAMPS 1.4
GND     ||     GND (AUX-7)
VCC     ||   5V-VCC(AUX-1)
SO/DO   || MISO-D50(AUX-3)
CS/SS   ||      D53(AUX-6)
SCK/CLK ||  SCK-D52(AUX-5)

That's how i wired mine, in Marlin 1.1 RC1 the CS-pin it's by default at D66, so you can use that or you can use whatever you want (as far as i know).

Marlin doesn't have implemented dual thermocouples, but i guess it shouldn't be a problem to wire everything in parallel with the exception of the CS, i'll guess someone has to test it. Rigth now i only have one MAX6675, so i can't help you with that.

Edited 1 time(s). Last edit at 10/06/2015 10:44AM by lynspyre.

Hi and sorry for digging up that thread.

I'm having issues with the MAX31855 at my RAMPS 1.4.
I wired everything up just as said, but there always is a Mintemp error thrown. I read tons of Marlin issues and it seems as some guys fixed it and implemented it to the newer versions of Marlin. Nevertheless I still get this error. Is it possible that I somehow destroyed my electronics or could it still be software related?
I am not using any LCD Display or SD Card.

(Sources: Max6675 SPI conflicts #1227, Release 1.1.0-RC4 #3104, Support MAX31855 as Temperature Sensor -3 #3112, MAX31855 ID 0 error #2726)

I am using this Breakout Board: Thermocouple Amplifier MAX31855 breakout board (MAX6675 upgrade) - v2.0

Edited 1 time(s). Last edit at 08/20/2016 09:38AM by derletztename.

Hi,

I'd readed that the MAX31855 is more user-friendly than MAX6675. Have you tried Repetier Firmware with your module?. I have had that error befor with the MAX6675 but in Repetier Firmware, and when crossing to Marlin the problem got solved.

I checked the syntax of both firmwares related to the MAX6675 and eveything was the same, but somehow in Repetier it doesn't work and in Marlin it does.

Hope this can help you.

And, in the error log you posted, i see that you have choosed MAX6675 instead of MAX31855, or at least that's what i understand.

Edited 1 time(s). Last edit at 08/21/2016 12:44PM by lynspyre.

Thanks for the answer.
I have some experience using Marlin but none with Repetier Firmware. Therefor I do not want to try Repetier if I don't have to. I would have to adjust all other settings to.
What do you mean by Error Code I posted? I just said that I received a Mintemp error. The Sources I posted were just things I found that might help to understand the problem. But I did not understand enough of it
Maybe I could run a M122 to get a diagnose or something, to get a error log from pronterface? Or is there some other way to gather more information about whats going on?
I am a little helpless with software and electronics

FWIW RepRapFirmware on Duet and Duet WiFi support up to 4 thermocouples or 4 PT100 sensors (with the appropriate interface boards), or a mixture of both. For the Duet WiFi you can get daughter boards containing either 2 thermocouple channels (using MAX31855 chips) or 2 PT100 channels (using MAC31865 chips), and you can fit 2 daughter boards. Details are at [duet3d.com] and [duet3d.com].

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I can't change to the Duet right now, but maybe later, when I want more features. Could I use Marlin with it?

Could you please explain how you connected the breakout board and set Marlin, lynspyre?
I just don't get it to work and it's really frustrating :´(
Maybe you even just could post the Marlin files you changed and I check it myself. It's only in the pins_RAMPS1.4.h and in config.h or anything else?

Hi derletztename,

In this post, in the beginning there is everything you need to know on how to wire the thermocuple module and how to configure it on Marlin RC1 (I guess it would be the same on the recent version of Marlin. Just check the pictures and the text below them.

I know, I already did it exactly this way. But still it's not running.
Maybe I have to do something else you forget to mention? Maybe set the temperature pin for heater 0 to 66 (53)? (which I already tried)
Or maybe I have to activate the sd card part of marlin somehow to get SPI connection working?
I already bought a second MAX31855 Breakout Board, in case it's just broken. But still it's the same issue. It's driving me crazy

There actually was an bug in Marlin:

Quote
Blue-Marlin commented 13 hours ago Try RCBugFix. When without SDSUPPORT there was a error in the initialization. (#4564)

https://github.com/MarlinFirmware/Marlin/issues/4744#issuecomment-243998297

You must check in the database of motherboards for the pinout of yours. Remember that RAMPS boards have made some upgrades of it's schematics, maybe there is where you are getting the error.
If you wire incorrectly the module you won't get any read from it.