3D Printer (RepRap) Monitor - Part 2 - HW Configuration

There are two variants of the RepRap Monitor with each being configurable in a number of manners.   The first of the two variants is a small PCB where the expectation is that a relay would be mounted off the board somewhere.  The second variant has room on the board for a relay and also provides a bypass switch that disables the shutdown function (assuming a switched power supply is connected).

The design for both PCBs is flexible in terms of power management strategy.  The primary configuration the PCBs are designed to handle entails that an ATX power supply is connected and the relay controls the switch circuit.   Obviously any power supply that provides a switch circuit would work.   The relay can also be used to control A/C power to the D/C power supply or the relay circuit could be used between the D/C power supply and the RepRap Controller (using two relays of appropriate capacity). 

Below is a picture of the larger PCB (with relay on the board) mounted on top of my Prusa I3's electronics stack.   In this implementation the gas and temperature sensors are surface mounted on the back of the PCB.   This places the temperature sensor at the very top of the electronics stack and the gas sensor a little higher.   The temperature sensor is focused on the controller but the gas sensor will react to issues from either the electronics stack or the print area.  The buzzer is mounted on the printer frame.

Here is a smaller PCB mounted on my Prusa I3 just above the electronics stack with the relay just below the monitor PCB.  The two sensors are on a stalk that is attached to the top of the printer controller.  The gas sensor is at the top of the stalk while the temperature sensor is inside the lower part of the stalk closer to the electronics.

The above pictures illustrate the two different PCBs as well as two strategies that can be used for mounting either PCB (remote sensors or surface mounted sensors).   Obviously there are a large number of other alternatives that can be employed to match a given configuration.  I will make the designs for mounts shown available (Sketchup).  These are designed to fit on a RAMPS board that is mounted vertically.

More in Part III

3D Printer (RepRap) Monitor - Part 1 - Introduction

My wife and I were sitting together in my office recently and as usual the 3D Printer was churning away.  Much to our surprise, and this has not happened before or since, the electronics stack started to smoke quite actively!  It turns out that one of the fuses at the top of the board had blown.  Puzzling as they are supposed to be self-resetting and they are not supposed to smoke to the point of flames!   It did NOT reset and it DID smoke!

In any case this was a little worrying, even without my wife sitting next to it!  I got an extra smoke alarm and installed it in the office but wanted to go a step further.   That step further was to design and build a circuit that would power down the printer on detecting heat or smoke.

Above is a picture of a prototype with all the components in place on the board itself.   I have chosen to use headers for the sensors, buzzer, LEDs, and the Arduino Nano though all or some of these components could be soldered directly to the board.   The sensors, reset switch, buzzer, and LEDs could also be mounted elsewhere with wiring back to the board.   It all depends on the implementation that is desired.

From the bottom right, and moving around counter clockwise, here are the elements of the circuit:

1. Pullup resistor for the temperature sensor
2. DHT-11 temperature sensor
3. Reset switch
4. Audible alarm buzzer
5. Green LED (behind buzzer)
6. Pullup resistor for the Green LED
7. Red LED (behind buzzer)
8. Pullup resistor for the Red LED
9. Relay
10. Arduino Nano
11. RS-232 monitoring connection
12. Relay connector (in my case triggers an ATX power supply but could switch A/C power with the right relay)
13. Gas sensor (I used the MQ-2 for smoke but other MQ sensors could be used for other types of gas in other applications)
14. Power connector 

More in Part II

Prusa I3 Improvements/Modifications

I have listed some of the modifications and improvements that I have added to my Prusa I3 but wanted to have a complete list at this point.   The things that I have mentioned before included the following:

• Filament roller
• Fan mount
• Heated bed adjusters
• Z-axis adjuster
• Flexible cord for x-axis servo
• Single board computer as controller (WiP)
• Screw panel for hot end replacement

Some other things that I have done either since the above of that I had not mentioned previously:

1. Improved fan mount - now have two small fans on the mount with one directed at the cooling fins on the extruder and the other on the print
2. Cooling fan for electronics stack with a master on/off switch.
3. Tie-down to heavy platform for stability.
4. Tensioner on the x-axis (downloaded from Thingiverse)
5. Tensioner on the y-axis (crafted myself)
6. Monitor to detect smoke or heat from the electronics and power down the printer (and sound an alarm)
7. Cork insulation under the heated bed
8. Cork insulator pad for top of heated bed (used when I rarely print with ABS or the heated bed takes forever to get to target temperature)
9. Forward frame tensioner to help eliminate some vibration artifacts in my prints.
10. Heated bed riser as the arms of the heated bed supports were dragging on the printer frame (downloaded from Thingiverse).

Photos are on the way for the things with no links.

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#2

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#5

#6 - Sensors

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#6 - Controller