Week 9 Assignment

OUTPUT DEVICES

This weeks assigmenat was to test output devices using different development boards so i stared with the neo pixel led that attached with my board,and i wanted to build something related to my project i tried to build a mosfet driver that i will used to test a spark generator

Group Assignment Week 9

Group Assignment

WS2812

WS2812 is a type of addressable RGB LED (Light Emitting Diode) commonly used in various lighting and display applications. These LEDs are often referred to as NeoPixels, a trademarked name by Adafruit, one of the leading manufacturers of WS2812-based products. The WS2812 LED integrates the LED die, control circuitry, and a communication interface into a single package, making it easy to control individual LEDs or groups of LEDs with a microcontroller or other digital control devices. Each WS2812 LED has a built-in shift register, which allows it to receive data serially and pass on the data to the next LED in the chain. One of the key features of WS2812 LEDs is their ability to be individually addressed, meaning that each LED in a chain can be assigned a unique color and brightness. This makes them ideal for applications such as LED matrix displays, decorative lighting, and wearable electronics. WS2812 LEDs communicate using a simple serial protocol, typically using a single data line to transmit color and brightness information to each LED in the chain. The communication protocol requires precise timing to ensure accurate data transmission, and there are various libraries and software tools available to simplify the process of controlling WS2812 LEDs with microcontrollers

sws2812 datasheet

WS2812 LIGHTUP

So i used a basic programme to light up and run a animation on the single led

this is the sketch that i used for the WS2812B individual addressable led

    
    #include Adafruit_NeoPixel.h

      // Pin connected to the NeoPixels (WS2812B)
      #define LED_PIN 15
      
      // Number of NeoPixels
      #define LED_COUNT 1
      
      // Create NeoPixel object
      Adafruit_NeoPixel strip(LED_COUNT, LED_PIN, NEO_GRB + NEO_KHZ800);
      
      void setup() {
        // Initialize NeoPixel strip
        strip.begin();
        strip.show(); // Initialize all pixels to 'off'
      }
      
      void loop() {
        // Cycle through different colors
        rainbow(20); // Change colors every 20ms
      }
      
      // Function to cycle through rainbow colors
      void rainbow(uint8_t wait) {
        for (uint16_t i = 0; i < 256; i++) {
          uint32_t color = Wheel((i + strip.numPixels()) & 255);
          for (int j = 0; j < strip.numPixels(); j++) {
            strip.setPixelColor(j, color);
          }
          strip.show();
          delay(wait);
        }
      }
      
      // Input a value 0 to 255 to get a color value.
      // The colors are a transition r - g - b - back to r.
      uint32_t Wheel(byte WheelPos) {
        WheelPos = 255 - WheelPos;
        if (WheelPos < 85) {
          return strip.Color(255 - WheelPos * 3, 0, WheelPos * 3);
        }
        if (WheelPos < 170) {
          WheelPos -= 85;
          return strip.Color(0, WheelPos * 3, 255 - WheelPos * 3);
        }
        WheelPos -= 170;
        return strip.Color(WheelPos * 3, 255 - WheelPos * 3, 0);
      }
      

  

HOW DOES THE CODE WORK

• #include Adafruit_NeoPixel.h: This line includes the Adafruit NeoPixel library, which provides functions to control WS2812B LEDs.
• #define LED_PIN 15: This line defines the pin to which the data line of the WS2812B LED strip is connected. In this case, it's pin 15.
• #define LED_COUNT 1: This line defines the number of LEDs in the LED strip. In this case, there is only one LED.
• Adafruit_NeoPixel strip(LED_COUNT, LED_PIN, NEO_GRB + NEO_KHZ800): This line creates a NeoPixel object named strip. It initializes the object with the number of LEDs (LED_COUNT), the pin connected to the LEDs (LED_PIN), and the color order and communication speed (NEO_GRB + NEO_KHZ800). Here, NEO_GRB specifies the color order (red, green, blue), and NEO_KHZ800 specifies the communication frequency (800 KHz).
• void setup(): This function is called once when the Arduino board starts up. It initializes the NeoPixel strip.
• strip.begin(): This line initializes the NeoPixel strip.
• strip.show(): This line sends the initial color data to all pixels in the strip, turning them off initially.
• void loop(): This function is called repeatedly in a loop after the setup() function. It contains the main code logic.
• rainbow(20): This line calls the rainbow() function with a delay of 20 milliseconds. This function changes the color of the LED strip in a rainbow pattern.
• void rainbow(uint8_t wait): This function defines the rainbow effect. It cycles through different colors of the rainbow with a delay specified by the wait parameter.
• for (uint16_t i = 0; i < 256; i++) { ... }: This loop iterates through 256 color values to create the rainbow effect.
• uint32_t color = Wheel((i + strip.numPixels()) & 255): This line calculates the color for the current position in the rainbow using the Wheel() function.
• strip.setPixelColor(j, color): This line sets the color of each pixel in the strip to the calculated color.
• strip.show(): This line updates the LED strip with the new color data.
• delay(wait): This line pauses the execution for the specified delay time.
• uint32_t Wheel(byte WheelPos): This function calculates the color for a given position in the rainbow. It takes a value between 0 and 255 and returns a corresponding color value. The colors transition from red to green to blue and back to red.

MOSFET DRIVER

as i was planning to build a mosfet driver as a part of my testing towards my final project i want to build a spark generator

MOSFET

A MOSFET, or Metal-Oxide-Semiconductor Field-Effect Transistor, is a type of transistor used for amplifying or switching electronic signals. It belongs to the family of field-effect transistors (FETs) and is widely used in various electronic circuits due to its high input impedance, fast switching speed, and low power consumption. MOSFETs consist of three terminals: the source (S), the drain (D), and the gate (G). The conductivity between the source and drain terminals is controlled by the voltage applied to the gate terminal. Depending on the type of MOSFET, this control can be accomplished by either applying a voltage (enhancement mode) or removing a voltage (depletion mode) at the gate terminal.

N-channel MOSFET (NMOS): In an NMOS transistor, the majority charge carriers (electrons) flow from the source to the drain when a positive voltage is applied to the gate terminal with respect to the source terminal. NMOS transistors are commonly used in digital circuits.

P-channel MOSFET (PMOS): In a PMOS transistor, the majority charge carriers (holes) flow from the drain to the source when a negative voltage is applied to the gate terminal with respect to the source terminal. PMOS transistors are often used in complementary metal-oxide-semiconductor (CMOS) logic circuits.

IMPORTENT SPECIFICATION

• Id(Package Limited): This is the maximum theoretical drain current for the package. You absolutely can’t exceed this value, but it does not mean you can actually drive a load at that current. The MOSFET will almost always burn up from heat before this spec is reached. So it must be taken with a grain of salt. The IRFS7530 has an Id of 240A, so we are good there.
• Vgs: Maximum voltage applied to the gate with respect to the source. It is ±20V for our MOSFET, and we are using a voltage of 12V, so we are not near the limit.
• Vdss: The voltage difference from the drain to the source can’t exceed, which is 60V in this case, well within our safe range.
• Rds(on): The maximum expected resistance from drain to source, at a given gate voltage. We find that the MOSFET has a worst-case Rds(on) of 1m4. Figure 6 shows a graph commonly found on MOSFET datasheets. We can see that the Rds(on) flattens out and has its the minimum value above ~8V. This is expected from a non-logic-level MOSFET and acceptable when driven at 12V.


Rds(on) vs Vgs at different temperatures

• RthetaJA (Junction-to-Ambient): This is the thermal resistance from the die junction to the outside of the package to ambient air. This will be specified with a specific amount of copper on the PCB.
• Qg: As previously mentioned, this is the total charge required to inject to the gate to fully turn the MOSFET "on". This takes into account the gate-to-source charge, gate-to-drain-charge, as well as any other internal parasitics. This is the easiest spec to use to calculate the maximum "theoretical" switching speed of the MOSFET.

BASIC MOSFET CIRCUITRY

N-channel MOSFET Circuit with PWM Control

• Identify MOSFET Pins:
  Identify the pins of your N-channel MOSFET. It typically has three pins: Drain (D), Source (S), and Gate (G).
• Connect Drain Pin:
  • Connect the Drain (D) pin of the MOSFET to the positive terminal of your power supply (+12V in this example).
• Add Resistor R1:
  • Place a resistor (R1) between the Gate (G) pin and the positive terminal of your power supply. This resistor helps limit the current flowing into the gate of the MOSFET and prevents it from getting damaged. A common value for this resistor is 10kΩ.
• Connect Load:
  • Connect your load (such as an LED) between the Source (S) pin of the MOSFET and the ground (GND). This is where the controlled current will flow through.
• Add Resistor R2:
  • Place a resistor (R2) between the Gate (G) pin and the Source (S) pin of the MOSFET. This resistor helps discharge the gate-source capacitance of the MOSFET when turning it off. A common value for this resistor is 1kΩ.
• Connect PWM Signal:
  • Connect the PWM signal source (e.g., from a microcontroller) to the Gate (G) pin of the MOSFET. This signal will control the MOSFET's switching using PWM.
• Complete Circuit:
  • Connect the negative terminal of your power supply to the ground (GND) and complete the circuit.
• Operation:
  • Apply a PWM signal to the Gate (G) pin of the MOSFET to control its switching and the average current flowing through the load.
  • The duty cycle of the PWM signal determines the average voltage applied to the Gate, thereby controlling the MOSFET's on-time and off-time.

  DESIGNING THE PCB

  Then i started with design a dedicated pcb that will used a at tiny 412 as a pwm driver that wil send pwm signals to the mosfet controlling the sparks, i fired up ki cad and started with the basic schematic i choose a n type mosfet with a SOT23 package and additional passive components is given below as bom, then i proceed with the pcb lay out and arranging the components and the i used the free route tool to route the pcb

  download Schematic from here

  then i procceed to get the the gerber files and then used our own fablabs gerber to png converts and got the necessary png files for milling, then i proceed to the modola milling machine and milled the pcb

  MISTAKES

  As I was working on designing the MOSFET driver circuit, I realized I overlooked a crucial aspect in the PCB layout phase. Specifically, I failed to add extra thickness to the pads and traces connected to the MOSFET pins. MOSFETs are often used in applications where they need to handle relatively high currents. However, I didn't take into account the need for thicker traces and pads to accommodate these high currents. By neglecting to add extra thickness, I risked several issues. Firstly, the thinner traces might not be able to handle the current flowing through them, leading to excessive heating and potential failure. Moreover, thinner pads might not provide a robust solder connection, further exacerbating the reliability concerns. Additionally, MOSFETs can generate significant heat during operation, especially if they're switching high currents rapidly. Thicker copper traces around the MOSFET pads would have helped dissipate this heat more effectively, preventing overheating and potential damage to the components. In hindsight, it's clear that adding extra thickness to the pads and traces should have been a priority during the design phase. It's a lesson learned for future projects, and moving forward, I'll be sure to pay closer attention to these critical details to ensure the reliability and performance of my PCB designs.

  

  ASSEMBLY

  i milled the pcb and got hold of the components iam yet to assemble the pcb