#Exercise_10

13/04/2016

Assignment

Measure something: add a sensor to a microcontroller board that you have designed and read it.

Design the controller board for the final project

For the assignment I decided to design the first prototype of the controller board that I will use for my final project. So I organized the two exercise, input and output devices together.

To control the pellet extruder I will need a ceramic heater cartridge in order to heat the noozle, a thermocouple to control the temperature, a thermistor or a temperature sensor to mesure the ambient temperature, a DC geared motor for the extrusion and a solenoid valve to cool the extruded material.

• 1 X Thermocouple J type
• 1 X Thermistor
• 3 X Ceramic heater cartridge 24V 40W
• 1 X DC geared motor 24V 5Nm Torque
• 1 X Solenoid valve
• 1 X Power supply 24V 15A
• IC1 AD594 Amplifier
• MICRO ATMEGA328P-AU
• Q1 16Mhz Crystal
• C1, C2 18pF
• C3, C4 100nF
• R1-R8 10K
• R8, R9 0ohm
• Q2-Q5 IRF3710S N-FET 100V 57A
• Q7 IOR
• D1-D5 DIODE 1N4001
• 7 X Screw terminal
• 1 X MTA02-156 male connector
• 1 X RJ45 female connector
• 1 X SMD male header 5X2 connector

Board: I decided to usa an ATMEGA328P-AU insted of using the Attiny44, because I will need a lot of PWM ports and the hardware serial, in order to allow the comunication between the robot and the control board.

To control the nozzle temperature I will use a thermocouple to allow a very accurate measurement; so I have installed the AD594 in order to read the data from the thermocouple type J.

To heating the nozzle I use 3 Ceramic heater cartridge, so I will need 3 mosfet to allow the control of the heating and other two to control the DC geared motr and the Solenoid valve.

Board: on the board I have used a couple of through hole components, and soldered bending the feet.

The ISP connector have 10 pins becouse I have added the RX an TX in order to allow the serial communication, that will used to communicate with the robot, but to make easier the wiring I have installed an RJ45 connector too. The robot core and the extruder control board will be 7m distant.

Milling: milling the board was pretty tricky, because the 328P-AU have a very tiny footprint, the pads are very close each oder (only 0,25mm). To mill the board I have used the same process described in the electronics production module.

Soldering: the board have a couple of wires on the bottom layer in order to connect the via. I have soldered all the screw connectors on the bottom layer.

As I immagin solder the 328P-AU was tricky too and took some times.

Some Problems: the first connection to the computer has not been a success, because I'm not been able to program the board. After a debug with the multimeter I discovered a short under the ISP connector; So I fix it cutting some tracks and soldering a couple of wires.

Input testing usign the serial communication, we can see the temperature increase using a lighter near the thermocouple.

Input testing usign the Arduino serial plotter, we can see the temperature increase on the chart using a lighter near the thermocouple.

					//define the thermoc. pin
					#define TC_1 A4
					
					void setup() {
					  //initializa the serial port
					  Serial.begin(9600);
					}
					
					void loop() {
					  //read the analago pin
					  int sensorValue = analogRead(TC_1);
					  //convert the voltage to temperature
					  float voltage = sensorValue * (5.0 / 1023.0) * 100.0;
					  //print the temperature on the serial monitor
					  Serial.println(voltage);
					  //wait a second
					  delay(1000);
					}