When Your Servo Motor Starts Acting Weird — How to Tell if It's Broken

🧠 The Situation

A new robotics enthusiast got a kit with two continuous rotation servos. When they plugged both into a microcontroller:

• Servo #1 just made a humming sound when commanded — but didn't move
• Servo #2 didn't move at first — but when plugged in alone, it worked perfectly
• When both were connected, only Servo #2 moved
• By hand, Servo #1 spun way more freely than Servo #2 — about 60% easier to turn

So… was one of the servos broken? Could it be fixed?

⚙ Understanding How a Servo Works

Let's start with the basics. Think of a servo as a smart motor that knows where it is.

Inside, it has:

1. A motor (the muscle)
2. A gearbox (to make it strong)
3. A sensor (to tell it its position)
4. A controller (to match what you tell it to do)

Most hobby servos — like the ones you use with Arduino — get a special pulse signal:

• A 1.5 ms pulse tells it "stay in the center"
• A shorter or longer pulse makes it turn one way or the other

In a continuous rotation servo, that feedback is removed so it spins freely, with pulse width controlling speed and direction instead of position.

🧩 The Clues

Now, back to the humming and lack of movement.

Experienced roboticists on forums pointed out that servos usually fail in two main ways:

In this case, the humming and easy hand rotation meant the gears were probably jammed or stripped.

🧰 The Fix

The community suggested opening up the servo carefully.

When the user did — they found jammed gears inside! 😅

They simply:

Lesson learned: Sometimes it's not an electrical issue at all, just a mechanical jam.

⚠ When Servos Really Die

If your servo exhibits any of these symptoms, it's likely gone for good:

• 🔥 Smells like burnt plastic
• ☁️ Emits a tiny puff of smoke
• 🔇 Stops responding even after checking all connections
• 🔌 Causes power brownouts for other devices when connected

Note: Most hobby servos ($10–$30) aren't worth repairing unless they're high-end ($100+).

🔍 Troubleshooting Flowchart

Does your servo respond to commands?
│
├─ No response at all?
│  ├─ Check power and signal connections first
│  ├─ Try a different servo socket (might be an Arduino pin issue)
│  └─ If still nothing → Likely dead (motor/electronics failed)
│
├─ Humming but not moving?
│  ├─ Turn it by hand — does it spin freely?
│  ├─ If YES (easy to turn) → Jammed gears (try disassembly)
│  └─ If NO (hard to turn) → Stuck gearbox or bearing failure
│
└─ Moving but erratically?
   ├─ Check for loose internal parts
   ├─ Verify servo signal pulse is correct (1.0–2.0 ms)
   └─ May be a stripped gear tooth or worn bearing

💡 Key Takeaways

✅ A humming servo that spins easily by hand = likely gear issue (fixable!)
✅ A completely dead servo = likely motor or electronics failure (retire it)
✅ Always try disassembly inspection before throwing it away
✅ Don't force servos under heavy continuous load — they can burn out
✅ Continuous rotation servos are tougher than position-feedback servos for heavy work

💬 Prevention Tips

• Avoid stalling your servo (motor pushing hard against resistance)
• Don't exceed recommended voltage or current draw
• Keep servos cool — they generate heat under heavy load
• Use quality servo arms and horns that won't strip
• Store servos in dry conditions (avoid moisture)

🧾 Final Thoughts

Sometimes, your robot's "broken" servo isn't dead—it's just stuck.

A little patience, a screwdriver, and some curiosity might save you a replacement.

Robotics, like life, is all about learning to listen when things hum instead of move. 😉

Based on a real discussion from Robotics Stack Exchange 🤖

#Robotics #ServoMotors #Troubleshooting #Repair #EngineeringSimplified