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bigtreetech / BIGTREETECH-OCTOPUS-Pro

This is OCTOPUS Pro open source material
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MAX31865 Reference Resistor #2

Open UrufuShinjiro opened 2 years ago

UrufuShinjiro commented 2 years ago

The value for the MAX31865 Reference Resistor is not noted as far as I can see, this is a needed value for configuration. Is it the standard 430 resistor or something else?

GadgetAngel commented 2 years ago

The value for the MAX31865 Reference Resistor is not noted as far as I can see, this is a needed value for configuration. Is it the standard 430 resistor or something else?

On page 19 of the Bigtreetech User guide (https://github.com/bigtreetech/BIGTREETECH-OCTOPUS-Pro/blob/main/BTT_Octopus_pro_EN.pdf) it states the following:

The PT100 amplifier supports 2,3 and 4 wire connections to the board. However, the DIP switch needs to be configured for the setup that you are using.

and farther done the page you will find a table which shows the proper configuration for the PT100/PT1000 DIP switch. The user guide also states the following:

Select the connection arrangement for your thermistor according to the table below. Bear in mind that you will still need to configure your firmware using the correct sense resistor values which will be 430 Ohms for the PT100 and 4300 Ohms for the PT1000.

Once you set the PT100/PT1000 DIP switch properly the appropriate Sense Resistor will automatically be used. But it is your responsibility to setup your firmware and tell your firmware which sense Reference Resistor is being used.

So if you set the PT100/PT1000 DIP switch to a setting that uses a PT100, then a 430 Ohm Reference Sense Resistor will be in the circuit. But If you choose a DIP switch setting that uses a PT1000, then a 4300 Ohm Reference Sense Resistor will be in the circuit.