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Four-Wheel RC Car Wiring

ESP32Intermediate2 hours
Photo of Four-Wheel RC Car Wiring

Schematik

Last updated July 17, 2026

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Build a WiFi-controlled four-wheel RC car powered by an ESP32 microcontroller. This project combines a LiPo battery, buck-boost converter, L9110S motor driver, and four geared DC motors to create a nimble platform that responds to web commands over a local access point.

The guide provides a complete wiring diagram showing power distribution, motor driver connections, and decoupling capacitor placement for clean operation. Builders will receive a parts list, step-by-step assembly instructions, and ready-to-flash firmware that hosts a web interface for forward, backward, left, and right control.

Wiring diagram

Wiring diagram for Four-Wheel RC Car Wiring

Gather all the parts

QtyComponent
1

LiPo 3.7V 1000mAh Battery

3.7 V protected 1S

Single-cell LiPo pack, nominal 3.7 V, 1000 mAh. Default rechargeable choice for portable ESP32 / Pico projects. Pair with a TP4056 charger for safe USB recharging.

1

Main SPST power switch

SPST

Single-pole single-throw main switch between LiPo positive and the switched motor/logic supply node.

1

3.3v Buck Boost

3.3 V, ≥1 A

TI TPS63030/TPS63031 high-efficiency single-inductor buck-boost converter family with 1A switches. Used to hold a regulated rail when battery voltage crosses above and below the target output.

1

L9110S dual-channel DC motor driver module

dual H-bridge

Dual H-bridge module. Channel A drives both left motors in parallel; channel B drives both right motors in parallel. Motor supply is the switched 1S LiPo rail; logic inputs use 3.3 V ESP32 GPIO.

1

Left-front 3–6 V geared DC motor

3–6 V geared DC

Tiny brushed geared DC drive motor; wired in parallel with the left-rear motor on L9110S channel A.

1

Left-rear 3–6 V geared DC motor

3–6 V geared DC

Tiny brushed geared DC drive motor; wired in parallel with the left-front motor on L9110S channel A.

1

Right-front 3–6 V geared DC motor

3–6 V geared DC

Tiny brushed geared DC drive motor; wired in parallel with the right-rear motor on L9110S channel B.

1

Right-rear 3–6 V geared DC motor

3–6 V geared DC

Tiny brushed geared DC drive motor; wired in parallel with the right-front motor on L9110S channel B.

1

470 µF electrolytic motor-supply capacitor

470 µF, ≥6.3 V electrolytic

Polarized bulk capacitor placed physically close to the L9110S VCC and GND pins to absorb motor transients.

1

100 nF ESP32 decoupling capacitor

100 nF ceramic

Ceramic decoupling capacitor across the regulated 3.3 V ESP32 supply, fitted close to the board power pins.

1

100 nF left-front motor suppression capacitor

100 nF ceramic

Ceramic capacitor directly across left-front motor terminals to reduce brush noise.

1

100 nF left-rear motor suppression capacitor

100 nF ceramic

Ceramic capacitor directly across left-rear motor terminals to reduce brush noise.

1

100 nF right-front motor suppression capacitor

100 nF ceramic

Ceramic capacitor directly across right-front motor terminals to reduce brush noise.

1

100 nF right-rear motor suppression capacitor

100 nF ceramic

Ceramic capacitor directly across right-rear motor terminals to reduce brush noise.

Assemble it in 6 steps

1. Prepare the power wiring

With the LiPo disconnected, wire battery +V (red, marked +) to the IN terminal of power_switch. Wire power_switch OUT as the switched-LiPo-positive junction. From this same OUT junction, run one wire to l9110s_1 VCC and one wire to buckboost_3v3 VIN. Wire lipo_1s GND (black, marked −), buckboost_3v3 GND, l9110s_1 GND, and the ESP32 GND pin into one common-ground junction.

  • Use heavier, short wire for the battery, switch, driver VCC, and ground paths because motor current flows there.
  • A star-like common-ground junction near the L9110S/battery return helps reduce motor noise.
  • Observe LiPo polarity. A reversed LiPo can destroy the converter and driver.
  • Do not connect the raw LiPo positive lead directly to the LOLIN S2 Mini 3V3 pin.
  • This parts list has no charging circuit: charge the protected LiPo only with a proper single-cell LiPo charger, disconnected from the car if the charger requires it.

2. Set and connect the 3.3 V converter

Before connecting the ESP32, power the switched input from the LiPo and use a multimeter to set buckboost_3v3 VOUT to exactly 3.3 V. Switch power off, then connect VOUT to the LOLIN S2 Mini 3V3 pin and leave its GND connected to the common-ground junction from step 1. Fit esp_decoupling_cap directly between the ESP32 3V3 and GND pins.

  • Keep the 100 nF ceramic capacitor leads very short.
  • If the chosen converter has an EN pin that must be driven high, follow its module markings; many modules already tie EN high.
  • Check 3.3 V with a meter before the ESP32 is attached. Never feed more than 3.3 V into its 3V3 pin.

3. Add driver supply filtering and logic wiring

Fit motor_bulk_cap close to l9110s_1: capacitor + to L9110S VCC and capacitor − to common ground. Observe its stripe-marked negative lead. Connect LOLIN S2 Mini GPIO9 to L9110S A-IA, GPIO10 to A-IB, GPIO11 to B-IA, and GPIO12 to B-IB. The driver and ESP32 grounds must remain common.

  • Keep the four GPIO control wires away from motor wires where possible.
  • The 470 µF electrolytic should be rated at least 6.3 V; 10 V or higher is also suitable.
  • The 470 µF capacitor is polarized: its negative-striped lead goes only to GND.
  • Do not use GPIO9–GPIO12 for another function in this build.

4. Wire channel A to both left motors

Make a parallel pair from L9110S channel A: connect A-OUT1 to left_front_motor M+ and left_rear_motor M+. Connect A-OUT2 to left_front_motor M− and left_rear_motor M−. Solder lf_motor_cap directly across the left-front motor terminals and lr_motor_cap directly across the left-rear motor terminals.

  • The two branch junctions at A-OUT1 and A-OUT2 are the required parallel connection for the left side.
  • Place each 100 nF capacitor physically on its motor terminals, not back at the driver.
  • The combined stall current of the left-front and left-rear motors must remain within the L9110S channel-current rating. Do not estimate from running current alone; use stall-current data or measure it.

5. Wire channel B to both right motors

Make a parallel pair from L9110S channel B: connect B-OUT1 to right_front_motor M+ and right_rear_motor M+. Connect B-OUT2 to right_front_motor M− and right_rear_motor M−. Solder rf_motor_cap across the right-front motor terminals and rr_motor_cap across the right-rear motor terminals.

  • Keep left and right motor-pair wiring similar in length and thickness.
  • Secure motor leads so vibration cannot fatigue the solder joints.
  • The combined stall current of the right-front and right-rear motors must remain within the L9110S channel-current rating. If either pair overloads the driver, use lower-current motors or a higher-current driver.

6. Check rotation and operate the car

Raise the car so all wheels are clear, turn on power, and use Schematik’s Deploy button to flash the firmware. On a phone, join Wi‑Fi network S2-RC-Car using password drivecar, then open http://192.168.4.1. Press Forward briefly. If one wheel turns opposite to the other wheel on the same side, switch off power and reverse only that motor’s two wires; keep its 100 nF capacitor across its two terminals.

  • Test while the wheels are off the bench first.
  • If forward/reverse is swapped for all four wheels, swap the forward/reverse logic in firmware rather than rewiring every motor.
  • Keep fingers, loose wires, and clothing clear of spinning wheels.
  • Stop immediately if the L9110S becomes very hot, the battery protection trips, or the ESP32 resets when accelerating.

Review all connections

1. Connections between "lipo_1s" and "ESP32"

Functionlipo_1sESP32
power+V → Main SPST power switch INEXT
groundGNDGND

2. Connections between "power_switch" and "ESP32"

Functionpower_switchESP32
powerOUT → L9110S dual-channel DC motor driver module VCCEXT
powerOUT → 3.3v Buck Boost VINEXT

3. Connections between "buckboost_3v3" and "ESP32"

Functionbuckboost_3v3ESP32
groundGNDGND
powerVOUT3V3

4. Connections between "l9110s_1" and "ESP32"

Functionl9110s_1ESP32
groundGNDGND
digitalA-IAGPIO 9
digitalA-IBGPIO 10
digitalB-IAGPIO 11
digitalB-IBGPIO 12
dataA-OUT1 → Left-front 3–6 V geared DC motor M+EXT
dataA-OUT2 → Left-front 3–6 V geared DC motor M-EXT
dataA-OUT1 → Left-rear 3–6 V geared DC motor M+EXT
dataA-OUT2 → Left-rear 3–6 V geared DC motor M-EXT
dataB-OUT1 → Right-front 3–6 V geared DC motor M+EXT
dataB-OUT2 → Right-front 3–6 V geared DC motor M-EXT
dataB-OUT1 → Right-rear 3–6 V geared DC motor M+EXT
dataB-OUT2 → Right-rear 3–6 V geared DC motor M-EXT

5. Connections between "motor_bulk_cap" and "ESP32"

Functionmotor_bulk_capESP32
power+ → L9110S dual-channel DC motor driver module VCCEXT
ground-GND

6. Connections between "esp_decoupling_cap" and "ESP32"

Functionesp_decoupling_capESP32
power13V3
ground2GND

7. Connections between "lf_motor_cap" and "ESP32"

Functionlf_motor_capESP32
data1 → Left-front 3–6 V geared DC motor M+EXT
data2 → Left-front 3–6 V geared DC motor M-EXT

8. Connections between "lr_motor_cap" and "ESP32"

Functionlr_motor_capESP32
data1 → Left-rear 3–6 V geared DC motor M+EXT
data2 → Left-rear 3–6 V geared DC motor M-EXT

9. Connections between "rf_motor_cap" and "ESP32"

Functionrf_motor_capESP32
data1 → Right-front 3–6 V geared DC motor M+EXT
data2 → Right-front 3–6 V geared DC motor M-EXT

10. Connections between "rr_motor_cap" and "ESP32"

Functionrr_motor_capESP32
data1 → Right-rear 3–6 V geared DC motor M+EXT
data2 → Right-rear 3–6 V geared DC motor M-EXT

Deploy the firmware

firmware.cppOpen in Schematik
#include <Arduino.h>
#include <WiFi.h>
#include <WebServer.h>

#define LEFT_IA_PIN 9
#define LEFT_IB_PIN 10
#define RIGHT_IA_PIN 11
#define RIGHT_IB_PIN 12


// Forward declarations
void stopCar();
void setLeft(bool forward);
void setRight(bool forward);
void handleCommand();
void handleRoot();

const char *AP_SSID = "S2-RC-Car";
const char *AP_PASSWORD = "drivecar";

WebServer server(80);

void stopCar() {
  digitalWrite(LEFT_IA_PIN, LOW);
  digitalWrite(LEFT_IB_PIN, LOW);
  digitalWrite(RIGHT_IA_PIN, LOW);
  digitalWrite(RIGHT_IB_PIN, LOW);
}

void setLeft(bool forward) {
  digitalWrite(LEFT_IA_PIN, forward ? HIGH : LOW);
  digitalWrite(LEFT_IB_PIN, forward ? LOW : HIGH);
}

void setRight(bool forward) {
  digitalWrite(RIGHT_IA_PIN, forward ? HIGH : LOW);
  digitalWrite(RIGHT_IB_PIN, forward ? LOW : HIGH);
}

void handleCommand() {
  String command = server.arg("c");

  if (command == "forward") {
    setLeft(true);
    setRight(true);
  } else if (command == "back") {
    setLeft(false);
    setRight(false);
  } else if (command == "left") {
    setLeft(false);
    setRight(true);
  } else if (command == "right") {
    setLeft(true);
    setRight(false);
  } else {
    stopCar();
  }

  server.send(200, "text/plain", "OK");
}

void handleRoot() {
  const char page[] = R"rawliteral(
<!doctype html><html><head><meta name="viewport" content="width=device-width,initial-scale=1">
<style>body{font-family:sans-serif;text-align:center;background:#151515;color:#fff;margin:0;padding:24px}button{width:120px;height:68px;margin:7px;font-size:20px;border:0;border-radius:10px;background:#2574d9;color:#fff}button.stop{background:#c93636}</style>
</head><body><h2>ESP32-S2 RC Car</h2><p>Hold a direction button to drive; releasing it stops the car.</p>
<div><button data-c="forward">Forward</button></div><div><button data-c="left">Left</button><button data-c="right">Right</button></div><div><button data-c="back">Reverse</button></div><div><button class="stop" data-c="stop">STOP</button></div>
<script>document.querySelectorAll('button').forEach(b=>{const go=()=>fetch('/cmd?c='+b.dataset.c);b.onpointerdown=go;b.onpointerup=()=>fetch('/cmd?c=stop');b.onpointerleave=()=>fetch('/cmd?c=stop');b.onpointercancel=()=>fetch('/cmd?c=stop');});</script>
</body></html>
)rawliteral";
  server.send(200, "text/html", page);
}

void setup() {
  pinMode(LEFT_IA_PIN, OUTPUT);
  pinMode(LEFT_IB_PIN, OUTPUT);
  pinMode(RIGHT_IA_PIN, OUTPUT);
  pinMode(RIGHT_IB_PIN, OUTPUT);
  stopCar();

  WiFi.mode(WIFI_AP);
  WiFi.softAP(AP_SSID, AP_PASSWORD);

  server.on("/", HTTP_GET, handleRoot);
  server.on("/cmd", HTTP_GET, handleCommand);
  server.begin();
}

void loop() {
  server.handleClient();
}

Download project files

stlschematikCAR.stl166 KBstlwheels.stl479 KB

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