week12 add content

content/WeeklyAssignments/week12.md

@@ -9,6 +9,25 @@ weight = 12
 
 ### Summary
 
+This week, I tested the addition of a sensor for my final project. I'm not
+sure exactly which sensors will be used, but it's to anticipate the measuring
+and setup.
+
+The result is shown below for the VMA320 sensor.
+
+<div class="row">
+  <div class="col-md-6 align-self-center" markdown="1" >
+    <img src = "./img/week12/SetupVMA320.jpg" alt = "SetupVMA320"
+class="mx-auto d-block">
+  </div>
+  <div class="col-md-6 align-self-center" markdown="1" >
+    <center>
+        <video width=95% controls muted loop>
+            <source src="./vid/week12/SensingTemp.mp4" type=video/mp4>
+        </video>
+    </center>
+  </div>
+</div>
 
 
 ***
@@ -26,8 +45,153 @@ that you have designed and read it.
 
 ***
 
-## Measuring High Voltage Output
-
 ## Probe Input Device
 
 This part was done in group and is accessible on the [group page](https://fabacademy.org/2024/labs/ulb/group-assignments/week12/).
+
+## Adding Input Device to my Board
+
+### Contexte of the Week
+
+This week I want to work on my project. It's more about being able to control
+plasma generation. I'll need to measure certain information, such as the
+temperature of the plasma reactor, or the amount of CO2 leaving the reactor
+(if the reactor is an open system).
+
+So I'm going to try and retrieve temperature information using two different
+temperature sensors: VMA320, and VMA324.
+
+These are two analog temperature sensors using a thermistor, a resistor that
+varies as a function of temperature.
+
+### Adding Temperature Sensor
+
+Adding one of these sensors is very simple. You need to supply the sensor with a
+DC voltage (3.3V or 5V). Then recover the output voltage with a final Pin. A
+temperature sensor using a thermistor works like a resistive divider. A schematic
+of the divider is shown below, in which we supply the divider with DC voltage Vin,
+and recover the output voltage Va, the voltage across the thermistor.
+
+The electronic diagram taken from the documentation is also shown below.
+
+<div class="row">
+  <div class="col-md-6 align-self-center" markdown="1" >
+    <img src = "./img/week12/Scheme.jpg" alt = "Oscillo1"
+class="mx-auto d-block">
+  </div>
+  <div class="col-md-6 align-self-center" markdown="1" >
+      <img src = "./img/week12/ResistifDiv.jpg" alt = "Oscillo2"
+class="mx-auto d-block" >
+  </div>
+</div>
+
+The setup, quite simple, is done separately from the board because it was
+a bit complicated to do due to a design problem (I wanted to display the
+temperature on an OLED screen but I didn't have enough inputs available).
+
+This setup can be seen below for the two sensors used.
+
+<div class="row">
+  <div class="col-md-6 align-self-center" markdown="1" >
+    <img src = "./img/week12/SetupVMA320.jpg" alt = "SetupVMA320"
+class="mx-auto d-block">
+  </div>
+  <div class="col-md-6 align-self-center" markdown="1" >
+      <img src = "./img/week12/SetupVMA324.jpg" alt = "SetupVMA324"
+class="mx-auto d-block" >
+  </div>
+</div>
+
+### From Analog Signal to Temperature
+
+I'll have to translate the sensor input signal into temperature in the code.
+To do this, I need to know how thermistors work. It turns out that by knowing
+the resistive value of the thermistor, we can know the temperature. You also
+need to know the manufacturer's reference point, in this case 25°C.
+
+The Steinhart-Hart relationship describes the relationship between resistance
+and temperature. It is given below.
+
+<img src = "./img/week12/SHlaw.jpg" alt = "SHrelation"
+class="mx-auto d-block" width =30% >
+
+This law integrates the parameters A, B and C, which are purely empirical and
+depend on each thermistor.
+
+A simpler version is possible and can be used over a smaller temperature range,
+incorporating only parameter B and a reference temperature and resistance value.
+This is what I'm going to use here.
+
+<img src = "./img/week12/SHlaw_Simplified.jpg" alt = "SHrelationSimple"
+class="mx-auto d-block" width =20% >
+
+### Programming Temp Sensor
+
+So I program the sensor using an adc object to read the sensor's analog
+value, which I transform directly into a voltage.
+
+With this voltage I can find out the resistance of the thermistor using ohm
+law and the reference provided by the sensor datasheet. Then I use the Steinhart-Hart
+relationship to obtain the absolute temperature and transform it into °C.
+
+```python
+import machine
+import ssd1306
+import time
+import math
+
+# Define the pins used
+ANALOG_PIN = 26
+
+# Define ref
+vRef = 5
+tRef = 25
+rRef = 10000
+
+# Define Steinhart-Hart parameters
+B = 3950
+
+# Initialize the OLED screen
+i2c = machine.I2C(1, scl=machine.Pin(7), sda=machine.Pin(6))
+oled = ssd1306.SSD1306_I2C(128, 64, i2c)
+
+# Function to read temperature from analog input
+def read_temperature(pin):
+    # Read analog value
+    adc = machine.ADC(pin)
+    value = adc.read_u16()
+    
+    # Convert analog value to voltage
+    voltage = value / 65535 * vRef  # Voltage in volts
+    
+    # Use the Steinhart-Hart formula to convert voltage to temperature
+    resistance = (vRef / (vRef - voltage)) * rRef # Resistance in ohms
+    temperature_kelvin = tRef + 1 / (1 / (273.15 + tRef) + 1 / B * math.log(resistance / rRef) )  # Temperature in Kelvin
+    temperature_celsius = temperature_kelvin - 273.15  # Temperature in degrees Celsius
+    return temperature_celsius
+
+while True:
+    # Read temperature
+    temperature = read_temperature(ANALOG_PIN)
+
+    # Clear the OLED screen
+    oled.fill(0)
+    
+    # Display temperature on the OLED screen
+    oled.text("Temp: {:.2f} C".format(temperature), 0, 0)
+    oled.show()
+    
+    # Wait for a few seconds before measuring again
+    time.sleep(0.1)
+```
+
+### Testing with My PCB
+
+I finally tested the sensors by touching the thermistor to provide heat.
+One of these tests can be seen in the video below.
+
+<center>
+    <video width=50% controls muted loop>
+    <source src="./vid/week12/SensingTemp.mp4" type=video/mp4>
+    </video>
+</center>

content/WeeklyAssignments/week8.md

@@ -440,21 +440,74 @@ Here's what I did:
 
 #### Coding the Python Programm
 
-Now it's time to code the program that will control the MOSFETs using PWMs.
-The code is fairly simple and uses only the machine library.
+Now it's time to code the program that will control the MOSFETs.
 
-*Add code*
+I thought it was going to be simple using the PWM objects in the machine library.
+It turned out to be more complicated than expected, as the PWMs work synchronously.
+In other words, it's not possible to delay the start of one pwm relative to another
+(between two output pins). So I have to go for "manual" control using the
+RP2040's PIO.
+I therefore work with a state machine, associating it with a function called square,
+which generates desynchronized square signs on two output pins. The square
+program is an assembler program.
 
-#### Testing & Measuring Signals
+```python
+from machine import Pin
+from rp2 import PIO, StateMachine, asm_pio
 
-For the tests, I decided to take a step-by-step approach, first testing the
-microcontroller outputs alone, and then testing the microcontroller on the board
+# Parameters
+frequency = 30_000
+count_TOT = 40
+FirstPin = 26
+
+# PIO function - PWM generation 
+@asm_pio(set_init=(PIO.OUT_LOW,PIO.OUT_LOW))
+def square():
+    set(pins, 0b0000)  [1]   # Deadtime
+    set(pins, 0b00001) [19]  # HalfPeriod
+    set(pins, 0b0000)  [1]   # Deadtime
+    set(pins, 0b00010) [19]  # HalfPeriod
+
+# Création d'une StateMachine pour générer les signaux en phase et en opposition de phase
+sm = StateMachine(0, square, freq= count_TOT * frequency, set_base=Pin(FirstPin))
+
+# Activation de la StateMachine
+sm.active(1)
+```
+
+So there are 4 assembler steps: two outputs off, one on, two off, and the other on.
+
+The frequency at which the state machine must run is that of the signal
+frequency multiplied by the number of steps in the square code.
+
+### Testing & Measuring Signals
+
+For the tests, I test the microcontroller on the board
 and measuring the signals at various points.
 
-##### Microcontroller Alone
+The measurement setup includes an oscilloscope and a test bench.
+
+<img src = "./img/week8/TestSetup.jpg" alt = "TestSetup"
+class="mx-auto d-block" width = 50% >
+
+And with the oscilloscope I look at different places to see what the
+signal looks like. I get signs that correspond to what is expected.
 
-*Add results*
+<div class="row">
+  <div class="col-md-6 align-self-center" markdown="1" >
+    <img src = "./img/week8/Oscillo_1.jpg" alt = "Oscillo1"
+class="mx-auto d-block">
+  </div>
+  <div class="col-md-6 align-self-center" markdown="1" >
+      <img src = "./img/week8/Oscillo_2.jpg" alt = "Oscillo2"
+class="mx-auto d-block" >
+  </div>
+</div>
 
-##### MiconController on Board
+Here you can see the two square signs at the microcontroller output, as well as
+the signs at the gates driver output (higher voltage). The shape of the gate
+driver signal is expected, given that the signal is high-frequency, and the
+gate driver rise time is noticeable.
 
-*Add results*
+A design error stopped me from testing further. I'll test this again in a
+future iteration, as it's for my final project.