Semester in Review
A look back at what we've learned and charts for the seas ahead.
Captain's Log: Key Learnings
Robots are Awesome
They can explore the deep seas, navigate dangerous terrain, and help us scale our human capabilities!
Robots are Complicated
It's not just magic; it's a complex integration of many moving parts working in harmony.
Inventories are Important
Knowing what you have, what you need, and where it is can make or break a mission. A good pirate always tracks their loot!
The Four Systems
A robot isn't just one thing. It is made up of:
- Mechanical Systems: The chassis, wheels, and gears (The Body).
- Electrical Systems: Batteries, wires, and drivers (The Energy).
- Computer Systems: The code and logic (The Brain).
- The Task: The specific mission they are going to accomplish!
Power Systems Lab
Calculating the energy needed to fuel the beast.
The Formula
P = V × I
Power (Watts) = Voltage (Volts) × Current (Amps)
Example: 12V × 5A = 60 Watts
Component Power Audit
| Component | Voltage (V) | Current (A) | Power (W) |
|---|---|---|---|
| Motors (4x @ 0.67A Stall) | 12 V | ~2.7 A | 32.2 W |
| Raspberry Pi | 12 V (Supply) | ~3.0 A | 36.0 W |
| Camera | 5 V | ~1.5 A | 7.5 W |
| Servos (3x) | 5 V | ~2.0 A | 10.0 W |
| ESP32 | 5 V | ~1.0 A | 5.0 W |
| Ultrasonic Sensor | 5 V | 0.5 A | 2.5 W |
| OLED Screen | 5 V | 0.5 A | 2.5 W |
| Buzzer | 5 V | 0.02 A | 0.1 W |
| ESTIMATED PEAK TOTAL | ~95.8 W |
* Note: This is peak power. Average usage likely 50-70% of this.
Battery Sizing 🔋
To determine the right battery, we verify the Voltage and calculate the Capacity needed.
1. Voltage Match
We have 12V motors and a 12V Pi standard. Our battery MUST be roughly 12V.
- 3S LiPo: 11.1V (Nominal) - 12.6V (Charged). Good Match
- 4S LiPo: 14.8V (Nominal). Requires Step-Down (Buck Converter) to safer 12V.
- 12V Lead Acid: Heavy, but 12V.
2. Current Draw (C-Rating)
Our peak current is roughly ~12.5 Amps (Sum of Amps column adjusted for voltage conversion).
A standard LiPo battery can easily handle 20A+ continuous discharge. Ensure your battery wiring is rated for this!
Captain's Recommendation
Current Configuration (Chosen):
3x 18650 Li-Ion Cells (2.55Ah each) in Series (3S).
- Voltage: ~11.1V Nominal (12.6V Max) ✓ Perfect
- Capacity: 2.55 Ah (2550 mAh)
- Total Energy: ~28.3 Watt-hours
- Max Current Draw: ~8.7 Amps (At Peak)
💡 Are they enough? YES!
The Math: Your robot needs about 8.7 Amps at peak. Most 18650 cells can handle 10-20 Amps easily.
Runtime: You have 2.55 Ah of fuel. Using 8.7 Amps continuously would last ~17 mins. Since you aren't always stalling the motors, expect 30-45 mins of playtime!