Final Project Development - The Notes

Tasks:
To complete the final project and tracking the progress:

• What tasks have been completed? And what tasks remain?
• What has worked? And what hasn't?
• What questions need to be resolved?
• What have been learned?

 

What tasks have been completed? And what tasks remain?

Tasks completed:

1. Found 1 old 3D Printer (Fab box - Solidoodle).




2. Purchased the relay module and line sensor.




3. Found PVC pipes and elbow from SP project store (left over from other project group).




4. Designed and milled ATmega 328P micro-controller board (modified from hello.arduino.328P)




5. Laser cut and coloured the rotating disk plate.




6. 3D printed the housing for relay module, tapered stoppers for line sensors and filament spool, brackets for filaments, etc.

 

Tasks to be completed:

1. Writing the programing sketch in Arduino IDE.
2. Testing the functionality of the "Inspector for 3D Printer" system.
3. Final packaging, documentation and presentation to everyone.

 

What has worked? And what hasn't?

1. Line sensor and relay module are tested working with Arduino UNO.
2. Self-made ATmega 328 micro-controller board is having error, ie. unable to burn bootloader.

 

What questions need to be resolved?

How to solve the bootloader issue?

 

What have been learned?

Alot had been learnt while in the progress to complete the task, ei. from self-reading, peers and "gurus". For examples, selection the right components/methods for a task (Where shall I position my relay module? on the AC side or DC side of the 3D printer; what is the better method to be used as an input to give signal to activate relay module? Weight sensor, IR sensor, Laser sensor.), trouble-shooting the sketch program, etc.

 

Notes Taken during the Development Process

Reflectance Line Sensor
Specifications:

• Operating voltage: 5.0 V
• Supply current: 25 mA
• Output format: digital I/O compatible
• Optimal sensing distance: 0.125" (3 mm)
• Maximum recommended sensing distance: 0.375" (9.5 mm)

The reflectance sensor has single infrared LED and a phototransistor pair. The phototransistor uses a capacitor discharge circuit that allows a digital I/O line on a microcontroller to take an analog reading of reflected IR by measuring the discharge time of the capacitor. Shorter capacitor discharge time is an indication of greater reflection.
The LED current-limiting resistor is set to deliver approximately 20-25 mA to the LED when VIN is 5 V. The current requirement can be met by some microcontroller I/O lines, allowing the sensor to be powered up and down through an I/O line to conserve power. The following shows the functional circuit diagram of the line sensor. More information can be found from this link.

Arduino library for the Pololu QTR reflectance sensors can be downloaded here. Unzipped the folder and place it at Arduino's libraries in local C:\ drive.

1-Channel Relay Module
Specifications:

• Control Voltage: 5V DC
• High Input voltage trigger
• On-board LED to indicate the working status
• Max. Control Capacity: 10A@250VAC or 10A@30VDC

A Relay is a digital switch to control higher voltages and currents than the normal boards does. When inputs a logic voltage, the relay will switch to allow current to flow or cutoff, depending on the wiring. A Relay usually consists of a coil, 1 common terminal, 1 normally closed terminal and one normally open terminal. When the coil is energized, the common terminal and the normally open terminal will have continuity. More information can be found from this link.

Power Supply for the 3D Printer
Specifications:

• Input voltage: 100-240VAC
• Input current: 2.5A
• Frequency: 50/60Hz
• Output voltage: 12VDC
• Output current: 10A

To decide wether the relay should be installed at the inlet or the outlet of the power supply. After some discussion and consultation with colleagues, the relay is placed at the outlet since it is DC (Direct Current) and has a much lower voltage. Thus, it is safer to install and also easier to find a relay.

 

The followings were the references read.

• QTR Application Note.
• Relay Module.