Electronics/WeevilEye

From Sequoia Fabrica

Weevil Eye[edit | edit source]

The monthly soldering class at Sequoia Fabrica is done with a beginner soldering kit called Weevil Eye. See the PDF for the full datasheet.

Weevil Eye Soldering Kit Instructions[edit | edit source]

Welcome to the Sequoia Fabrica's soldering kit class! In this guide, we will walk you through each step to assemble your Weevil Eye kit. This project is great for beginners and will help you get comfortable with soldering and understanding basic electronic components.

Safety Guidance[edit | edit source]

  • Work Area: Ensure you have a clean, well-ventilated workspace.
  • Safety Gear: Wear safety goggles to protect your eyes from flying wires (as they are being cut), fumes, and potential molten solder splashes.
  • Soldering Iron: Always place the soldering iron on a stand when not in use. Keep it away from flammable materials.
  • Solder Fumes: Avoid inhaling solder fumes by working in a well-ventilated area or using a fume extractor.
  • Burns: Be cautious as the soldering iron tip is extremely hot. Never touch the tip and avoid accidental contact with your skin.
  • Wash Hands: Once the class is over be sure to watch you hands after handling solder. Do no touch your eyes or face while handling solder.

Components Overview[edit | edit source]

  • PCB (Printed Circuit Board): The board where all components are soldered.
  • Resistors: Control the flow of electric current.
  • LEDs (Light Emitting Diodes): Emit light when current passes through.
  • Battery Holder: Holds the battery that powers the circuit.
  • Transistor: Acts as a switch or amplifier in the circuit.
  • Photoresistor (LDR): Changes resistance based on the intensity of light it is exposed to.

Step-by-Step Assembly[edit | edit source]

Step 1: Get your Tools and Supplies

  • Soldering iron
  • Stand for soldering iron
  • Solder wire
  • Cleaning steel ball
  • Wire cutter
  • Tweezers
  • Heat resistant mat
  • Safety glasses
  • Weevil Eye soldering kit

Follow these steps to get ready to start on the project.

  1. Gather tools and supplies.
  2. Ensure collar on solder iron is tightened.
  3. Wear eye protection.
  4. Place the stand for your solder iron.
  5. Plug in the solder iron and put onto holder.
  6. Wait a moment for the iron to heat up.
  7. Test melting a bit of solder on the tip of the iron.
Tools and supplies

Step 2: Identify Components[edit | edit source]

Before you start soldering, identify all the components and their placements on the PCB. Refer to the labels on the PCB for guidance. It is marked to guide you.

  1. Take the components out of the bag on the mat at your workstation.
  2. Place your components on the heat resistant mat in the boxes at the top of the mat to prevent them rolling away.
Step 2
Components

Step 3: Solder the Resistors[edit | edit source]

See that the PCB has 2 spaces marked 220 and one with 47K. Compare your 3 resistors to identify the 2 matching resistors. A resistor can be positioned either way.

  1. Identify the Resistors: You should have resistors with color bands indicating their resistance value (47K, 220 ohms, etc.).
  2. Place the Resistors: Insert the resistor leads into the corresponding holes on the PCB.
  3. Solder the Resistors: Turn the PCB over and solder the leads. Ensure a good solder joint by heating both the pad and the lead, then apply solder.
  4. Clear excess wires: Safely cut away the excess wire. (eye protection is recommended)
  5. Check connections: Check if separate solder rings are connected and use solder sucker as needed to clear excess solder.
Step 3
Resistors

Step 4: Solder the LEDs[edit | edit source]

The PCB has a flat side for the circle around the LED solder rings. The flat side is the negative side. The short wire goes on the flat side while the positive goes into the other.

  1. Identify the LEDs: Note the longer leg (anode) and shorter leg (cathode). The longer leg goes into the positive hole marked on the PCB.
  2. Place the LEDs: Insert the LEDs into the PCB. Ensure the correct orientation.
  3. Solder the LEDs: Solder the leads and trim the excess.
Step 4
LEDs

Step 5: Solder the Transistor[edit | edit source]

  1. Identify the Transistor: It has three leads and may have a flat side for orientation.
  2. Place the Transistor: Insert it into the PCB, ensuring the flat side aligns with the PCB marking.
  3. Solder the Transistor: Solder the leads and trim the excess.
Transistor
Transistor

Step 6: Solder the Photoresistor (LDR)[edit | edit source]

  1. Identify the Photoresistor: This component changes resistance based on light.
  2. Place the Photoresistor: Insert it into the PCB.
  3. Solder the Photoresistor: Solder the leads and trim the excess.
Photoresitor
Photoresitor

Step 7: Solder the Battery Holder[edit | edit source]

  1. Identify the Battery Holder: This holds the coin cell battery.
  2. Place the Battery Holder: Insert it into the PCB, ensuring correct orientation.
  3. Solder the Battery Holder: Solder the leads securely to the PCB.
Battery Holder
Battery Holder

Step 8: Final Check[edit | edit source]

  1. Inspect Solder Joints: Ensure all solder joints are shiny and free of cold solder joints (dull or cracked).
  2. Check Component Placement: Verify all components are correctly placed and oriented.
Step 8
Final Check

Step 9: Insert the Battery[edit | edit source]

  1. Insert the Coin Cell Battery: Ensure the correct polarity, with the positive side facing up.
  2. Test the Circuit: The LEDs should light up when the battery is inserted.

Congratulations! You have successfully assembled your Weevil Eye soldering kit. Enjoy your new creation and the basics of electronics and soldering!

Step 9
Insert Battery

Step 10: Join the Online Community

  1. Join Open Circuit SF on Discord to stay in touch.
  2. Take a photo of your project and post it in the soldering channel to show off your work.
  3. Share what you'd like to do next with Sequoia Fabrica.

Important: Be sure to wash your hands to clean off any lead-based solder.

Step 10
Join the Community

Weevil Eye Circuit on a Breadboard[edit | edit source]


The Weevil Eye circuit on the breadboard has a light-sensitive circuit that uses a photoresistor (LDR) and a transistor to control LEDs based on ambient light levels. Here is an explanation of the connections and components:

  1. Battery Holder (CR2020): Supplies power to the circuit. The positive terminal is connected to the positive rail of the breadboard, and the negative terminal is connected to the negative rail.
  2. Transistor (NPN, probably a 2N3904): The transistor acts as a switch to control the LEDs based on the input from the photoresistor. The three pins of the transistor are:
    • Collector (C): Connected to the negative lead of the LEDs.
    • Base (B): Connected to the photoresistor through a current-limiting resistor (usually 4.7k ohms).
    • Emitter (E): Connected to the negative rail of the breadboard (ground).
  3. Photoresistor (LDR): Senses ambient light. One lead is connected to the positive rail of the breadboard, and the other lead is connected to the base of the transistor through a current-limiting resistor.
  4. LEDs: The positive lead of each LED is connected to the positive rail of the breadboard through current-limiting resistors (usually 220 ohms), and the negative lead is connected to the collector of the transistor.

Connections:

  1. Transistor Base to Photoresistor:
    • The photoresistor is connected to the positive rail and the base of the transistor through a current-limiting resistor. When light falls on the photoresistor, its resistance changes, affecting the current flowing to the base of the transistor.
  2. Transistor Collector to LEDs:
    • The collector of the transistor is connected to the negative lead of the LEDs. When the transistor is turned on, current flows from the positive rail through the LEDs and the collector-emitter path of the transistor to ground, lighting up the LEDs.
  3. Transistor Emitter to Ground:
    • The emitter of the transistor is connected to the ground rail of the breadboard. This completes the circuit for the current flowing through the LEDs and the transistor.

Explanation of Connections:

  • Base (B): The base of the transistor receives a small current from the photoresistor. The amount of current depends on the light level falling on the photoresistor.
  • Collector (C): The collector is connected to the LEDs, which will light up when the transistor is turned on.
  • Emitter (E): The emitter is connected to ground, completing the circuit.

In summary, when light levels are high, the resistance of the photoresistor decreases, allowing more current to flow to the base of the transistor. This turns the transistor on, allowing current to flow from the positive rail through the LEDs, lighting them up. When light levels are low, the resistance of the photoresistor increases, reducing the current to the base of the transistor, turning it off, and the LEDs remain off.

Weevil Eye on Breadboard
Weevil Eye on Breadboard