The schematic has been arranged automatically. Flux can redraw it to be more readable, with components placed in related groups and wires drawn more legibly. This takes about 10-60 mins.
Project Specification
Status: Finalized for PCB layout and manufacturing validation
Project Overview
Chakra Brain is a rugged, serviceable 100 × 100 mm, two-layer through-hole carrier PCB for a student robotics kit. It sockets one ESP32 DevKitC-VE, two Pololu #713 TB6612FNG dual motor-driver carriers, and one Pololu #5719 S9V11E2A adjustable buck-boost module.
Approved Architecture
Board: exactly 100 × 100 mm, Standard 2 Layer, conventional drilled through-hole vias.
Four M3 3.2 mm NPTH mounting holes, one near each corner.
Two independent external power inputs with common ground:
J11: regulated 5 V logic input, pin 1 positive and pin 2 GND.
J10: nominal 8 V motor input, pin 1 positive and pin 2 GND.
No onboard battery connector, master-switch loop, RJ45 jack, LEDs, magnetics, or shield terminals.
All carrier-board discretes and connectors are through-hole. SMT internal to socketed modules is permitted.
Power Tree
Diagram
The Pololu #5719 module is adjusted to 5.0 V before U1 is installed. Its VIN and EN are tied to J11 pin 1; VOUT feeds 5V0. The module accepts 5 V input while regulating 5 V output and is rated about 1.7 A continuous under typical near-equal input/output conditions after startup.
Motor Control and Ports
U2 drives M1 and M2; U3 drives M3 and M4.
M1 / J3: U2 AO1 → contact 3, U2 AO2 → contact 4.
M2 / J4: U2 BO1 → contact 3, U2 BO2 → contact 4.
M3 / J5: U3 AO1 → contact 3, U3 AO2 → contact 4.
M4 / J6: U3 BO1 → contact 3, U3 BO2 → contact 4.
On every 6P6C jack, contacts 1, 2, 5, and 6 are intentionally NC.
Custom jack footprint is controlled by the user drawing: two staggered rows of three signal holes, 1.27 mm adjacent-column pitch, 2.54 mm row separation, and two mechanical holes on 12 mm centers. Numbering is viewed from the component side.
Remote Breakout
J2 is only a bare 1 × 8, 2.54 mm through-hole socket/header:
F1: through-hole Littelfuse MINI blade holder populated with a 5 A fuse; protects the approximately 4 A aggregate continuous motor branch while allowing brief startup pulses.
Q1: through-hole FQP47P06 P-channel MOSFET for whole-board motor-input reverse-polarity protection. Drain faces fused input and source faces the protected motor rail.
R1: 100 kΩ through-hole gate-to-source resistor for Q1.
D4: through-hole P4KE10A TVS across the protected motor rail; 8.55 V stand-off, 9.5–10.5 V breakdown class.
C1/C3: 330 µF, 16 V radial bulk capacitors local to U2/U3 VMOT.
C5: 470 µF, 10 V radial bulk capacitor on 5V0 for ESP32 and breakout load transients.
C7: 10 µF, 10 V radial bulk capacitor on the ESP32 3.3 V breakout rail.
The Pololu TB6612 carriers already include supply filtering and motor-supply reverse protection. The carrier-level VM bulk capacitors are retained for wiring inductance and simultaneous motor transients; redundant small decouplers are not added.
Electrical Limits
TB6612 carrier recommendation: 4.5–13.5 V motor supply and 2.7–5.5 V logic supply.
Each TB6612 channel is about 1 A continuous. The advertised 3 A value is a brief peak, not a 2 A continuous rating.
Motor connectors are rated 1.5 A and should not be treated as suitable for sustained currents above that rating.
Recommended external supplies: regulated 5 V / 2 A logic source and nominal 8 V / 5 A motor source with wiring sized for the fuse.
PCB Layout Requirements
Motor jacks and both power terminals at accessible edges.
ESP32 antenna at an outer edge with no copper or components beneath/in front of the antenna region.
U2/U3 near their paired motor connectors.
Motor power/protection grouped separately from logic and remote analog breakout paths.
Wide copper for the 8 V trunk, common motor return, and motor outputs; normal signal widths for GPIO.
Bottom-layer GND fill or equivalent continuous return where routing permits.
Clear top silkscreen: 5V POWER, 8V MOTOR, +/−, M1–M4, socket/module orientation, and pin 1.
Manufacturing
Primarily through-hole hand assembly; all carrier discretes are through-hole.
Standard FR-4 prototype process, 1 oz copper minimum, standard drilled vias.
Modules are installed in female sockets after their orientation and output adjustment are verified.