Arduino Wiring Questions

ok we are setting up our electronics, and have a couple questions. We are looking at this document here.

This shows a thermistor, are we best off using a thermister or a thermocouple? If it is a thermocouple where do I find information on this?

This also shows a dc motor driver for a dc motor, but i am pretty sure the setup uses a stepper motor with a stepper motor driver, where do I see the provisions for this?

The opto endstops report to the stepper driver boards then to the PIC, is this just a thought and through operation, or do the driver boards condition the signal? We are using different stepper drivers as we couldn't get the ones specifically for this project.

I am getting the feeling I am looking at the wrong schematic

Thanks in advance.

A few things have changed and so the schematic is out of date. You have to figure out each of these on its own as it seems the generation 2 stuff is not being updated much.

You can use a stepper motor driver instead of a DC motor driver for the extruder. The PWM pin on the DC motor driver becomes the STEP pin on the stepper motor driver. DIR becomes DIRECTION. MIN and MAX are not used for the extruder and don't need to be connected to anything. ENABLE is used, and must be assigned a pin in the firmware in pins.h; this is how the firmware knows you are using a stepper and not a DC motor.

The signal on the opto endstops can skip the stepper driver board and go straight to the Arduino, they just pass through. I believe the reason these are on the stepper driver board is to give you a nice connector with GND, signal and +5.

I've got no experience with a thermocouple so I can't comment on your first question.

Edited 1 time(s). Last edit at 12/14/2009 03:21PM by mccoyn.

excellent thanks. Does anyone know about the thermocouple?

from what I've read, the thermocouple is the best approach. thermistors seem to be very finicky to get an accurate reading from, and even the best ones are only rated to 300c so they run extremely close to their maximum rating (even if your heater is set to 220c, the nature of bang-bang control means the thermistor may see peaks of over 300c. PID should help with this)

I have a max6675 coming for my mendel. max6675 is a digital thermocouple receiver that gives the temperature between 0c and 1024c in 0.25c increments over SPI. it's cheaper than the ad595 (locally anyway), and means even less of the temperature path is analog.