how to make maths working model on prime numbers using led lights

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In this video, we show how to make an amazing Maths Working Model that identifies Prime Numbers and Non-Prime Numbers using LED lights, metal nails, and a simple touch-probe switch.
When you touch the probe to any number, the Green LED glows for Prime numbers and Red LED glows for Non-Prime numbers.

1) MATERIALS REQUIRED

Electronics

  • 9V Battery
  • 2 LED bulb caps OR bright 5V LEDs
    • 1 Green
    • 1 Red
  • 2 × 220Ω resistors (for LEDs)
  • nails
  • Wires (red & black)

Mechanical

  • Chart board / cardboard sheet
  • Foam sheet for border
  • Metal nails (one nail per number)
  • Hot glue gun
  • Wooden probe (thin bamboo stick)
  • A piece of copper wire to wrap at probe tip (acts as touch conductor)

2) BASIC WORKING PRINCIPLE

The probe carries +9 volts.
Each nail is connected to a diode that leads either to:

✔ Green LED driver → if number is prime

✔ Red LED driver → if number is not prime

Touching probe to a nail sends +9V through the correct diode → transistor → correct LED lights up.

4) BOARD MAKING STEPS (Exactly like picture)

STEP 1 — Prepare display board

  • Take a chart board or cardboard.
  • Wrap with black paper for clean background.
  • Add blue foam sheet border like image.
  • Divide into two columns

STEP 2 — Fix number plates

  • Cut small white rectangles
  • Outline with pink sketch (same as your picture)
  • Write numbers (94, 89, 37, 99, 53… etc.).
  • Paste them in two vertical rows.

STEP 3 — Insert nails

  • Make holes next to each number label
  • Insert nails so only the metal head is visible
  • Hammer gently so they stay firm
  • Inside the board, connect wires to each nail

These nails become touch switches.

STEP D — Connect all NON-PRIME nails

Nail → Diode → BR (base of RED transistor)

Non-prime numbers in picture:
11, 62, 81, 83, 78, 67, 100, etc.

These → connect to red base node (BR)

6) PROBE MAKING (Important)

  • Take a bamboo stick
  • Wrap copper wire at the tip (only 1–2 cm exposed)
  • Connect wire from tip → +5V supply
  • Insulate entire stick except tip
  • This is your metal touch probe

Now whenever probe touches a nail → that nail gets +5V.

7) FINAL ASSEMBLY

✔ Glue wires neatly
✔ Add a base stand (foam board + cardboard)
✔ Add labels:

PRIME NUMBERS
NOT A PRIME NUMBERS
Math’s Project Prime Numbers

✔ Hide electronic parts inside the base

8) TESTING

  1. Power the circuit with 5V.
  2. Touch probe to a prime nail → Only green light turns ON.
  3. Touch probe to a non-prime nail → Only red light turns ON.
  4. No light?
    • Check diode direction
    • Check base resistor
    • Check transistor pins (C-B-E)

https://www.youtube.com/@howtofunda

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