Shashank Rover: a Chandrayaan-inspired Moon Rover (Space Contest Instructable)

Welcome to the Shashank Rover project! Homage to ISRO’s Chandrayaan mission, channeling the spirit of Pragyan while staying builder-friendly. Shashank Rover features tank-like wheels with protective overcovers, an expressive OLED screen "eye," Bluetooth control, and a servo-operated robotic arm. This project celebrates space exploration and robotics, perfect for makers who want to bring a bit of the cosmos to their desktop.

Why Chandrayaan inspiration? Pragyan’s compact 0.9 × 0.75 × 0.85 m form factor, slow and deliberate mobility (~1 cm/s), stereo navcams, and south-pole mission goals embody efficient design and purposeful exploration—values echoed in Shashank’s simplicity and clarity of function.

Electronics

1. 2 × Arduino Nano (or Nano Every)
2. 1 × 0.96" I2C OLED (SSD1306) for “eyes”
3. 2 × DRV8833 motor drivers (each handles 2 motors; total 4 motors)
4. 1 × Micro servo (SG90 or metal gear micro servo for “hand”)
5. 1 × HC-05 Bluetooth module (or HM-10 BLE alternative)
6. 4 × N20 metal gear motors (e.g., 6V 200–300 RPM for desktop use)
7. 4 × N20-compatible wheels (rubber tires)
8. 1 × 2S 7.4V LiPo (with switch) + 5V buck converter (3A recommended) OR 2×18650 with BMS and 5V buck
9. Perforated protoboard, breadboard/jumpers, headers, wiring
10. On/off switch, LEDs for status (optional)
11. Piezo buzzer (optional)

Hardware and Fabrication

1. 5 mm sunboard/foamboard or 3 mm acrylic for chassis
2. Top canopy and tank-like wheel overcovers (foamboard or 3D printed if preferred)
3. M2.5/M3 screws and stand-offs, tiny screws for motor clamps
4. Hot glue, super glue, double-sided tape
5. Small hinges for servo hand linkage (or 3D printed bracket)
6. Cutting tools, soldering iron, wire stripper

Software

1. Arduino IDE with libraries: Servo.h, Adafruit GFX + Adafruit SSD1306 (or U8g2), SoftwareSerial (if needed)
2. Android Bluetooth RC Car app by ANDI.co (or any serial BT joystick app)
3. Optional: Autodesk Fusion 360 for chassis CAD to qualify for Autodesk Design & Make Award

Design Highlights (Pragyan-inspired)

1. Low-profile body with forward “sensor bar” look. OLED replaces navcams for animated eye expressions, nodding to Pragyan’s stereo cameras and situational awareness.​
2. Tank-like wheel overcovers tribute to dust mitigation covers and iconic rover silhouettes.
3. Front micro-servo “hand” for simple “scoop/gesture” demos, aligning with rover manipulation metaphors (not a true regolith sampler).
4. Split-brain architecture: One Nano for motion + servo timing; second Nano dedicated to OLED animations and UI—mirroring the reliability-first separation of concerns seen in real missions.

1. Base plate
2. Cut a 100 × 70 mm base from 5 mm sunboard. Mark mounting for four N20 motors at corners (inboard by ~8–10 mm).
3. Add side rails (100 × 20 mm) to stiffen the base.
4. Upper deck and canopy
5. Mid-deck (90 × 60 mm) for electronics.
6. Canopy (90 × 60 mm) with a front aperture for the OLED “eye.” Leave ventilation slots.
7. Add standoffs between base and mid-deck for wire clearance.
8. Wheel overcovers
9. Cut two long side overcovers (100 × 35 mm). Arch cutouts over wheels; leave 5–7 mm clearance above tire.
10. Glue to side rails. Ensure wheel removal is still possible.
11. Servo hand mount
12. Front-center bracket for micro servo horn to extend a simple arm or scoop.
13. Reinforce with small L-brackets or layered foamboard.

Tip: Keep CG low by placing battery on the bottom deck; drivers and Nanos on mid-deck; OLED and servo forward.

1. Mount 4×N20 motors so left pair share a common axis and right pair share the opposite axis to enable skid steering.
2. Use wheel hubs designed for N20 shafts; add a dab of threadlocker on set screws.
3. Check freewheel clearance against overcovers; adjust overcover cutouts as needed.
4. Route motor wires inward to DRV8833 boards on mid-deck.

Why 4-wheel skid-steer? Simple, robust, and evokes tracked rover dynamics at desktop scale while remaining builder-friendly.

Power

1. Battery → main switch → 5V buck converter → logic rail (Nanos, OLED, servo).
2. DRV8833 VMOT can take 5–10.8 V; for uniformity, feed ~7.4 V from 2S LiPo to VMOT and 5V to logic (check your driver revision).
3. Common ground across everything.

Microcontrollers

1. Nano A: Motion + Servo
2. Controls both DRV8833 drivers (4 motors) and the servo hand.
3. Receives Bluetooth serial commands from HC-05.
4. Nano B: Display
5. Drives OLED animations (eyes, status icons).
6. Optional serial input from Nano A for status cues.

Modules and Buses

1. HC-05 to Nano A via Serial (hardware or SoftwareSerial on pins 10/11).
2. OLED to Nano B via I2C (A4 SDA, A5 SCL on classic Nano).
3. Optionally link Nano A TX to Nano B RX for sending simple status chars.

DRV8833 (x2)

1. Driver 1 controls Left Front (M1) and Left Rear (M2).
2. Driver 2 controls Right Front (M3) and Right Rear (M4).
3. For each channel: AIN1/AIN2 (or BIN1/BIN2) to Nano A PWM-capable pins; AO1/AO2 to motor leads.
4. EN pins may be tied high or controlled for braking; consult board pinout.

Bluetooth HC-05

1. VCC 5V, GND common.
2. TXD → Nano A RX, RXD ← Nano A TX (use voltage divider on HC-05 RX if required).
3. Pairing default PIN 1234/0000.

Servo

1. 5V and GND to logic rail, signal to a PWM pin (e.g., D9 or D10) on Nano A.

OLED

1. VCC 5V (or 3.3V per module), GND, SDA → A4, SCL → A5 on Nano B.

Power discipline

1. Use a 3A buck for servo current spikes.
2. Add 100 µF–470 µF electrolytic near drivers and 10 µF near each Nano.
3. Verify common ground across battery negative, buck negative, drivers, and both Nanos.

Separating motion control from display ensures jitter-free PWM for motors/servo while maintaining smooth 30–60 fps OLED eye animations. This improves responsiveness and resembles the subsystem segregation in real exploration systems.

Bluetooth command map (example):

1. ‘F’ forward, ‘B’ back, ‘L’ left, ‘R’ right, ‘S’ stop
2. ‘1’..‘9’ speed levels, ‘q’ max
3. ‘W’/‘w’ servo sweep up/down
4. ‘G’/‘I’ gentle arc turns

Sketch outline:

1. Define motor pins for AIN1/AIN2/BIN1/BIN2 across two DRV8833 boards.
2. Implement setMotor(channel, speed, dir).
3. Parse Serial.read() for commands and set speeds accordingly.
4. Servo write for hand gestures; include timed sweeps.

A reference motor/servo control structure similar to the attached robot’s sample is appropriate for fast iteration, with fixes to duplicate-case issues and consistent mapping.

1. Use Adafruit SSD1306 + GFX or U8g2 to render:
2. Idle blinking eyes
3. “Scan” animation bars
4. Arrow/chevron when moving forward/back
5. Status icons (BT connected, battery, stop)
6. Optionally read a status byte from Nano A (via serial) to switch expressions dynamically.

Pseudoflow:

1. Setup I2C display; draw eyes as two rounded rectangles or circles.
2. Timer-based blink every 3–6 seconds.
3. If move command active, animate pupils or add motion lines.
4. Minimal frame buffers to keep FPS stable.

1. Fix drivers to mid-deck using stand-offs; route motor leads neatly.
2. Mount OLED behind canopy aperture; add light baffle to improve contrast.
3. Secure HC-05 where antenna is unobstructed.
4. Place battery low and central; ensure easy access to charging lead.
5. Verify wheel free-rotation; check overcover clearances while turning.

1. Pair HC-05 (PIN 1234/0000) via phone.
2. Use “Bluetooth RC Car” by ANDI.co to send basic F/B/L/R/S and speed keys, or a joystick layout if supported.
3. Test:
4. Low-speed crawl forward/back.
5. Left/right skid turns.
6. Servo hand actuation.
7. OLED animations responding to states.

If drift occurs, calibrate motor polarity and PWM curves; consider deadband and ramping. For smoother starts, implement acceleration ramps in code.

Shashank Rover is a creative tribute to space exploration and ISRO’s Pragyan rover. It combines simple robotics techniques with space mission inspiration for a classroom or desktop project that’s both educational and fun.