Build a servo robot arm

Build a 4-servo desktop arm from a kit, give the servos their own power, steer it live with four knobs, then teach it a sequence of poses and play them back.

Time2–3 weekends

Parts₹1,756–1,916

Servos centred on their own power19 wires, 7 actions · read it below
Arm assembled at the centre8 actions
Safe angle limits found6 actions
Live control with four knobs15 wires, 6 actions
Record and play back4 wires, 6 actions
Pick and place on its own6 actions

Start this build

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Before you start

Tools: Laptop with the Arduino IDE, Multimeter, Small cross-head (Phillips) screwdriver, Small spanner or pliers for M3 nuts, An eraser and a cup for the final test
Skills: A first servo project. No soldering, unless your knobs have solder tabs. Steps 1, 3, 4 and 5 use code (or Get the code).
Safety: Low voltage at the arm: 5 V servos, fed from a 12 V plug-in adapter. Use a closed, shop-bought adapter and never open it. The joints and the gripper pinch: keep fingers clear while it's powered, and unplug the adapter if a servo buzzes or grinds.
Prices: Checked 2026-10, with a clone Uno and 4 SG90 servos; 4 MG90S metal-gear servos give the top figure. The arm kit comes without servos or a board. An original Uno adds about ₹1,950

Step 1 of 6

Servos centred on their own power

The four servos run from their own 5 V supply with a shared ground, and all sit at 90° before any of them goes into the arm.

Build it

Task 01 of 07

Look at a servo's three wires: brown is −, red is +, orange is the signal. Put a piece of tape on each servo and write B (base), S (shoulder), E (elbow) or G (gripper) on it.

Check: Four labelled servos, no horns fitted yet.

Steps
Wires · 2
Steps
Wires · 17
Steps

You need

Arduino Uno R3 and USB cable
4 × SG90 or MG90S micro servos (SG90 is safest here: four MG90S can stall at about 2.8 A, near the 5 V converter's limit)
12 V 2 A plug-in adapter (5.5 mm barrel plug)
DC barrel jack to screw terminal adapter (female)
Buck converter module, 6–24 V in, 5 V 3 A out
1000 µF 25 V electrolytic capacitor
830-point breadboard and jumper wires (male-to-male and male-to-female)

DC jack −
DC jack +
Breadboard top − rail
Breadboard top + rail
Uno pin 3
Uno pin 5
Uno pin 6
Uno pin 9
Uno GND

Buck converter IN−
Buck converter IN+
Buck converter OUT−
Buck converter OUT+
Capacitor − (striped side)
Capacitor + (long leg)
Base servo − (brown)
Base servo + (red)
Base servo signal (orange)
Shoulder servo − (brown)
Shoulder servo + (red)
Shoulder servo signal (orange)
Elbow servo − (brown)
Elbow servo + (red)
Elbow servo signal (orange)
Gripper servo − (brown)
Gripper servo + (red)
Gripper servo signal (orange)

Serial monitor

9600 baud

Expect to see

All four servos centred: not seen yetAll four servos are at 90. Fit the horns now.

Get the codeThe full sketch comes with the build.

Build a servo robot arm

Parts list

Servos centred on their own power

Build it

Serial monitor