Build a Motorised Pulley Lifting System!
Lift objects with a spinning motor and a rope — using just a relay, push buttons, and a DC motor. Real engineering, zero Arduino!
What is a Pulley Lifting System? 🧐
A pulley is one of the six simple machines — it uses a wheel and a rope to lift heavy things with less effort. You've probably seen them on cranes, elevators, and flagpoles!
In this project, we swap the human pulling the rope with a DC motor. A relay module acts like a smart switch that lets our push buttons control which direction the motor spins — lifting or lowering!
⚡ Key Concept — What is a Relay?
A relay is an electrically controlled switch. When you apply a small voltage to it, it switches a bigger circuit ON or OFF. We use two relays to control the motor's direction: Relay 1 → Motor goes UP, Relay 2 → Motor goes DOWN.
How Does It Work? 🔬
Press Button
You press the UP or DOWN push button
Relay Triggers
The relay coil gets power and its switch flips
Motor Spins
Motor spins clockwise (up) or anticlockwise (down)
Load Lifts!
The rope winds around the spool, lifting the load
Why Two Relays?
A DC motor's direction depends on which terminal gets + and − power. By using two relays in an H-Bridge-style relay pair, we can flip which wire gets + and which gets −, making the motor spin both ways!
Components You Need 🛒
| # | Component | Price (₹) | Where to Buy |
|---|---|---|---|
| 1 | DC Gear Motor (3–6V, slow RPM) with spool/shaft | ₹80–120 | Robocraze / Amazon |
| 2 | 2-Channel 5V Relay Module | ₹50–70 | Robocraze / Flyrobo |
| 3 | 9V Battery + Clip | ₹30–50 | Local electronics shop |
| 4 | 5V USB Power Bank (for relay power) | Already at home! | — |
| 5 | Push Buttons × 2 (momentary, 12mm) | ₹10–20 | Flyrobo / SP Road |
| 6 | Pulley Wheel (plastic, ~4 cm) | ₹20–40 | Hardware shop / Amazon |
| 7 | Thick String / Thread (~1 m) | ₹5 | Any stationery shop |
| 8 | Wooden Planks (for frame, ~30×20 cm) | ₹40–60 | Carpenter / hardware shop |
| 9 | Jumper Wires (M-M, M-F) | ₹30 | Any electronics shop |
| 10 | Small plastic container (as the "load bucket") | ₹0 | Recycle from home! |
Eco Tip!
Use old wooden ice cream sticks, cardboard, or scrap wood for the frame. Robotics doesn't have to be expensive!
How to Connect Everything
🗺️ Pulley Lifting System — Full Circuit
🔴 Red wire = Positive (+) | ⚫ Black wire = Ground (−) | 🟡 Yellow = IN1 signal | 🟢 Green = IN2 signal
Pin Connection Table 📋
| From | Pin/Terminal | To | Wire Colour |
|---|---|---|---|
| 9V Battery | Positive (+) | Relay Module COM (both relays) | Red |
| 9V Battery | Negative (−) | Common GND rail | Black |
| 5V USB Bank | 5V Out | Relay Module VCC | Red |
| 5V USB Bank | GND | Relay Module GND & button commons | Black |
| UP Button | One leg | Relay IN1 | Yellow |
| UP Button | Other leg | GND | Black |
| DOWN Button | One leg | Relay IN2 | Green |
| DOWN Button | Other leg | GND | Black |
| Relay 1 | NO (Normally Open) | Motor Terminal A (+) | Green |
| Relay 2 | NO (Normally Open) | Motor Terminal B (+) | Orange |
| Motor | Terminal A | Relay 1 NO | Blue |
| Motor | Terminal B | Relay 2 NO & 9V− via relay COM swap | Orange |
Important Safety Rule!
Never press BOTH buttons at the same time! This short-circuits the motor. Always press only ONE button — UP or DOWN — at a time. Ask a parent or teacher to supervise when you first connect the 9V battery.
The Direction Trick — How Two Relays Replace a Motor Driver
Professional robots use a chip called an H-Bridge to control motor direction. But we can do the same thing with just two relay switches! Here's the magic:
Step-by-Step Build Instructions 🔧
Build the Wooden Frame 🪵
Cut two vertical planks (~25 cm tall) and one horizontal plank (~20 cm wide). Join them in a ∩ shape (like a goalpost). This is your crane tower! Sandpaper the edges so they're smooth.
Mount the Pulley Wheel 🎡
Fix the plastic pulley wheel at the top centre of your frame using a bolt or thick nail through its centre. It should spin freely — try spinning it with your finger. The rope will loop over this wheel.
Attach the DC Motor 🔩
Mount the DC gear motor at the TOP of one vertical plank, so its shaft (the spinning bit) points inward toward the pulley. Use zip ties, hot glue, or small brackets. Cut a small notch in the frame if needed.
Wind the Rope 🧵
Tie one end of the string/thread firmly around the motor shaft (a few loops, then a tight knot). Run the rope up and over the pulley wheel. Tie a small plastic container (your "bucket") to the hanging end.
Wire the Relay Module ⚡
Place the relay module on the base of your frame. Connect the wiring exactly as shown in the pin table above. Double-check every connection before powering on — use the colour-coded guide!
Mount Your Push Buttons 🔘
Push the two buttons through small holes drilled in a side plank, or tape them to a small cardboard "control panel". Label one ▲ UP (green) and one ▼ DOWN (red).
Power Up & Test! 🚀
Connect your 5V USB bank to the relay module first, then connect the 9V battery. Press the UP button — the motor should spin and the bucket should rise. Press DOWN — it should lower. 🎉
Motor Not Spinning?
Check that the relay clicks when you press the button (you'll hear a small "click"). If no click: check IN1/IN2 wiring to the buttons. If click but no spin: check the 9V battery connection to the relay COM pins.
No-Code Version? Yes! But Here's a Bonus Auto-Stop Feature 🧾
The basic pulley works with zero code — it's purely a physical circuit! But if you want to add an automatic safety stop (so the motor cuts off after 3 seconds to protect the rope), you can add a 555 Timer IC — or if you ever do add a small microcontroller like a Digispark (not Arduino Uno!), here's the logic in pseudocode:
// ════════════════════════════════════════════════════ // Pulley Lifting System — Relay Logic Explanation // MakeMindz | No-code, no-Arduino version // How the circuit behaves step by step: // ════════════════════════════════════════════════════ // COMPONENT SETUP: Relay Module = 2-channel, Active LOW IN1 pin = connected to UP button → GND IN2 pin = connected to DOWN button → GND VCC = 5V from USB power bank GND = shared GND (battery + USB bank) // ── WHEN UP BUTTON IS PRESSED: ────────────────── IN1 goes LOW (0V) → Relay 1 coil activates → COM₁ connects to NO₁ → 9V+ flows to Motor Terminal A → Motor Terminal B stays at 9V- → Motor spins CLOCKWISE → Rope winds UP around spool → Load RISES ⬆️ // ── WHEN DOWN BUTTON IS PRESSED: ──────────────── IN2 goes LOW (0V) → Relay 2 coil activates → COM₂ connects to NO₂ → 9V+ flows to Motor Terminal B → Motor Terminal A now at 9V- → Motor spins ANTICLOCKWISE → Rope unwinds from spool → Load LOWERS ⬇️ // ── WHEN NO BUTTON IS PRESSED: ────────────────── IN1, IN2 both HIGH (5V via pull-up) → Both relays OFF → No current to motor → Motor STOPS ✋ → Load stays at current height // ══ SAFETY RULE ═════════════════════════════════ // ❌ NEVER press both buttons simultaneously! // This would connect 9V+ to both motor terminals // at once → short circuit → damage battery/motor // ═════════════════════════════════════════════════
What is "Active LOW"?
Most relay modules trigger when the IN pin receives LOW voltage (0V or connected to GND), not HIGH. That's why we connect the button between IN1 and GND — pressing the button pulls the pin LOW and fires the relay!
Cool Upgrade Ideas
Auto-Stop Timer
Add a 555 Timer IC to automatically cut the motor after 3 seconds so the rope doesn't over-wind.
LED Indicator Lights
Wire a green LED for UP and a red LED for DOWN so you can see the system status at a glance.
Load Limit Switch
Add a microswitch at the top of the frame that auto-stops the motor when the bucket reaches the top.
Bluetooth Control
Replace the push buttons with an HC-05 Bluetooth module and a Digispark to control from your phone!
Buzzer Alert
Wire a piezo buzzer to beep when the motor is running — like a real crane reverse alarm!
Double Pulley
Add a second pulley wheel to create a block-and-tackle system that halves the load on the motor.
What Science Topics Does This Cover? 📚
Frequently Asked Questions
Do I need any coding experience for this project?
No! This project works without any code at all. It's a pure hardware circuit using a relay module and push buttons. The logic is all done by the relay switches, making it perfect for complete beginners!
Why does my motor not change direction?
Most likely the IN1 and IN2 wires are swapped. Try swapping the wires going to IN1 and IN2 on your relay module. Also check that your relay module is "Active LOW" type — when you press the button, that IN pin should go to GND (0V).
Can I use any DC motor?
Use a DC gear motor (slow RPM, high torque) for best results. Fast motors like hobby motors spin too fast and the rope flies off the spool. A motor running at 30–100 RPM works perfectly for a lifting system.
What can I put in the load bucket?
Start with very light things — a few coins, a small eraser, a folded piece of paper. A small gear motor can typically lift 50–200 grams depending on its torque rating. Check your motor's datasheet for the exact lifting limit!
Is this project safe for kids?
Yes, as long as an adult helps with cutting the wood and making the first battery connection. We use only 9V and 5V — both are completely safe for humans to touch accidentally. Just never short circuit the battery terminals!
Why do I need two separate power sources (9V battery AND 5V USB bank)?
The relay module's control circuit (coils, logic) runs on 5V. The motor itself needs more power (9V) to spin strongly. Mixing them can cause the relay to behave erratically or the motor to underperfom. Keeping them separate is the professional way to wire it!
My relay clicks but the motor doesn't spin. What's wrong?
If the relay is clicking (you can hear it), the signal side is working. Check the power side: make sure your 9V battery is fresh (test it with a multimeter if possible), and that the wires from relay COM and NO are firmly connected to the motor terminals.
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