Max31855 Configuration

3ghendricks

Arduino Mega
Ramps 1.4
RepRapDicount

2 Extruders
2 type K thermocouples with MAX31855

So after starting into 3D printing a week ago I am now trying to configure my Ramps to allow for 2 thermocouples. I have read everything I can find but nothing really explains how to hook up the MAX and how to set the inputs.

I used the configuration tool to set the temperature sensors for MAX31855 and the pin assignments to Analog 10 and 12

I have the Max hooked up as follows

Vin -- AUX-2 5V
GND -- AUX-2 GND
DO -- AUX-3 MISO
CS -- AUX-2 A10
CLK -- AUX-3 SCK

I am only trying to get one to work first then I thought I would parallel the common pins and use AUX-2 A12 for the other CS on thermocouple 2.

So far it doesn't give a reading, does anyone have information about how this is done?

RAyWB

Think you fried the devices....

refer MAX31855 Datasheet :

https://cdn-shop.adafruit.com/datasheets/MAX31855.pdf<br/><br/>They are not useable on 5V Systems ....

3ghendricks

Okay I will try the other one with 3.3, the back of the board even says, "Vin: 3-5VDC" There is a pin that says 3.3 I'll just voltage divide down to that one.

Any ideas on pin configuration in the firmware?

RAyWB

ok, i saw different types of the breakout board , some with the level shifting , some without, but both sold as 3-5V :-(

so may be you can send a link with picture of the board.

configuration in Configuration.h

search for:

#define SUPPORT_MAX31855 (should not be commented)

sensortype should be set to 102

as far as i can see the max 31855 support uses Hardware SPI , so on ramps it would be aux3 , cs to pin53

(just took a look to development code) so may be you check cs on 53 first , seems only 1 of the 31855 supported

3ghendricks

It's an Adafruit MAX31855, I have the LCD on the AUX3 ports, will this interfere? That's why I was wondering if AUX2 could maybe be used.

http://imgur.com/a/5Q4ju

RAyWB

so on the adafruit board level shifting is done, no problem.
take care, 3v pin on this board is OUTPUT. don´t use it.

aux 3 is occupied by sd-card...
mosi,miso and clk can be used multiple(on avr), cs not
so just don´t plug in the sd, use pin53 for cs and just see what happens