Enclosure controller

As mentioned in an earlier post I have a plan to add an Arduino Uno based controller for enclosure. Its responsibility is to monitor temperature, control ventilation fan speed and switch on the main relay. It also has a simple 1602 LCD display shield for temperature and other information. At the moment I haven't planned any use for the keys of the display shield.

So far I have been testing the design on a breadboard in order to get temperature reading and relay control working. I have plenty of 100k Ohm NTC 3950 thermistors so I used one to measure temperature using voltage divider circuit and Steinhart–Hart equation in the Arduino code. There are plenty of examples online how to wire this up.

The main relay is an automotive 40A relay with integrated fuse socket. The funny thing was it actually came with a 30A fuse. That should be enough, though. In order to energise the coil of the relay I used BC548 NPN transistor. I also added 1N4148 as a flyback diode.

Adding a PWM controlled 12V should be straightforward. I will use BC548 or BC639 but I might add a capacitor to smooth out the fan control. After I have that sorted out on the breadboard I'll solder everything together.

Polarity matters

I was reorganising the cabling after I installed the cooling fans next to the hot end. I checked there were no loose ends and everything seemed to be fine. But as soon as I turned the PSU on there was a faint popping sound and no lights on the LCD. I managed to connect wires from PSU to RAMPS wrong way and that instantly fried RAMPS.

Looks like the LCD and MEGA are okay though, I was able to turn them on with USB power and use different features on the controller. However, none of the steppers move and the hot end wont warm up. Just to make sure I decided to order new RAMPS, MEGA and stepper drivers again. This will mean couple weeks pause with printing but I'll use that to design and build an enclosure for the printer.

Printrun issues with USB connection and OS X

I spent quite some time trying to get Printrun to connect my RAMPS board. The fix was to set the baud rate lower with #define BAUDRATE 115200 both in Marlin Configuration.h and in Pronterface user interface.

The screenshot below shows necessary details:

But the while I was testing some models there were long pauses in the print. Those were long enough to clog the hot end as the heating was on but no filament was pushed through. After couple attempts I started to use SD-card reader on the LCD display unit.

Marlin firmware

In order to get Arduino Mega clone and RAMPS board to function properly I need to install a firmware to Arduino. There are several choices but I decided to start with Marlin. It seems to be actively maintained and has good support.

I downloaded release version 1.0.2 and started to work with the configuration file. I did not modify too many settings at this point. I only selected correct motherboard settings and enabled LCD support. After uploading the firmware I disconnected Arduino and pressed the RAMPS board on it. I also hooked up the LCD screen cables and powered everything up. The LCD lit up and the menu was operational so I guess it works ok.