Electronics
Controller
I want a 32-bits controller board for the printer. One on which I can choose my own motor driver boards. I found RAMPS-FD 1.0, a cheap RAMPS-based board that can be piggybacked on a 32 bits Arduino Due board. You can not use a normal RAMPS board with an Arduino Due, because the Due runs on 3.3 instead of 5 volt. After buying the RAMPS-FD I found out that this 1.0/1.2 version of the board is not safe to use. More information here:http://reprap.org/wiki/RAMPS-FD. Because now that I have the Arduino Due, I started looking for another board that piggybacks the Arduino Due. I found the RADDS (RepRap Arduino-Due Driver Shield) 1.5 board.
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| Figure 2: RADSS wiring |
Power supply unit (PSU)
Because of the heated bed, a beefy PSU is needed that can provided enough amps. I choose a 24 volt, 15 ampere LED strip PSU (360 Watt). 24 Volt because it does heat up the hotend and bed faster. Connect the PSU to the two print screw terminals of the RADDS board in the upper right en left corner, see figure 2.
Mounting the PSU to the frame
Looking for a way to mount the PSU, I came across these brackets on thingiverse to mount the PSU inside the base triangle, underneath the heated bed. After printing the brackets and mounting the PSU I found out that there is not much room left. I started looking for designs that keep the PSU on the outside of the printer frame. These brackets were just what I was looking for. Too bad they did not fit my PSU. I designed a parametric version of these brackets using OpenSCAD. You can create your own version of it in Thingiverse Costumizer.
To wire the PSU to mains I found a PSU inlet and switch on thingiverse that I liked, but it needed some adjustments. Luckily the OpenSCAD files were provided, so I was able to do that. The good thing about this mains inlet unit, is that it also contains a switch and a fuse.
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| The PSU mounted to the Z-tower of the frame |
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| Closeup for the PSU mounted to the frame |
Wiring the PSU to mains and adding a switch and fuse
To wire the PSU to mains I found a PSU inlet and switch on thingiverse that I liked, but it needed some adjustments. Luckily the OpenSCAD files were provided, so I was able to do that. The good thing about this mains inlet unit, is that it also contains a switch and a fuse. |
| PSU inlet and switch |
Endstops
Normally closed
I have the wires mounted such that the circuit is closed when the switch is not pressed. Pressing the switch opens the circuit. The advantage of this solution is that in the event of a broken wire/connection the motor won't move, because the controller detects an open circuit. When I had chosen the other option, in case of a broken circuit, the motor would run, but won't stop at the endstop switch. My switch has the outer most connections for normally closed. |
| Figure 4: endstop switch on endstop holder |
Endstop wiring
Connect the endstop wires to the controller board between Signal and GND. Make sure to enable the pull up resistors on the controller board. In the drawing below you find the position of the X, Y and Z endstops. Connect to X, Y and Z-max on the controller board. |
| Figure 5: position of the X, Y and Z-endstop. |
Endstop configuration in the firmware
I use Repetier firmware. The endstops can be configured using the Repetier webpage: |
| Figure 6: Repetier endstop configuration. Click to enlarge. |
Endstop tesing
After everything is connected and the firmware uploaded, the endstops can be tested:- Connect to the printer (using Proterface for example)
- Send M119 command.
- Firmware should report back status "0" or "open".
- Engage the endstop by pressing the switch.
- Send M119 again.
- Firmware should report "1" or "triggered" or "closed".
Crosstalk
Twist the endstop wires (as well as the motor wires) to reduce crosstalk. Crosstalk can cause false readings of the endstop data.Resouces:
http://reprap.org/wiki/Endstophttp://reprap.org/wiki/G-code#M119:_Get_Endstop_Status
Motors
X,Y and Z motor
I bought Wantai 42byghw811 stepper motors at RepRapWorld.The order of connecting the wires for the Wantai motors is (figure 7):
- Black
- Green
- Blue
- Red
Microstep configuration
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| Figure 7: connecting the X, Y and Z stepper motor |
Extruder motor
Motor drivers
My Prusa I2 has motor drivers based on the A4988 chip. This board has a maximum microstepping resolution of 1/16-step.
For this printer I bought stepper drivers based on the DRV8825 chip. That has a maximum microstepping resolution of 1/32-step.
Note that the X, Y and Z stepper driver boards have to be mounted with the potentiometer on the left for the A4988 based boards, and on the right for the DRV8825 based boards.
The board for the extruder has to be paced 180 degrees rotated on the RAMPS FD.
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| Figure 8: steppers divers based on DRV8825 chip |
Cooling
All extruder outputs (D9, D10 and D11) on the RAMPS FD are inverted in the firmware. That is why you cannot use them easily for a cooling fan. Use the extra MOSFET outputs (D12 and D2 for that purpose).
More information in these posts:
http://forums.reprap.org/read.php?267,459760
https://github.com/repetier/Repetier-Firmware/issues/277
Hotend fan
The hotend always needs to be on. So connect it PSU.Object fan
The object fan needs to be on for materials like PLA, except for the first layer. This fan needs to be managed be the controller board.http://reprap.org/wiki/G-code#M106:_Fan_On
M106 Set Fan Speed to S and start <PWM Value[S 0-255]>
M107 Turn Fan off
firmware:
#define FAN_BOARD_PIN -1
#define FAN_BOARD_PIN -1
#define FAN_BOARD_PIN 10
Fan for the controller board
For now I don't have a fan for the controller board itself. The motor driver board get hot, I have read that this is normal.
