• Fits Sensor: HC-SR04 (standard 45×20 mm face with 2 transducers)
• Fits Servo: SG90 (horn + screws)
• Assembly: Attach HC-SR04 to bracket face (screws/nuts); fix bracket to SG90 horn; secure horn to servo.
• Orientation: Keep transducers level; route wires to avoid fouling the horn.
• Standoffs: Use spacers if the sensor PCB touches horn screws.

Use thread-locker sparingly on metal screws. Do not overtighten into plastic.

Power the SG90 from a separate 5–6 V rail. HC-SR04 runs at 5 V; add a divider on ECHO for 3.3 V MCUs.

Scan with SG90 + HC-SR04

#include <Servo.h>
Servo pan;
const int SERVO_PIN=9, TRIG=6, ECHO=5;

long pingUS(){
  digitalWrite(TRIG, LOW); delayMicroseconds(3);
  digitalWrite(TRIG, HIGH); delayMicroseconds(10);
  digitalWrite(TRIG, LOW);
  return pulseIn(ECHO, HIGH, 30000UL); // 30 ms timeout
}

void setup(){
  Serial.begin(115200);
  pinMode(TRIG, OUTPUT); pinMode(ECHO, INPUT);
  pan.attach(SERVO_PIN);
  pan.write(90); delay(500);
}

void loop(){
  for(int a=30; a<=150; a+=5){
    pan.write(a);
    delay(180);
    long us = pingUS();
    float cm = us ? us/58.0 : -1;
    Serial.print("A:");Serial.print(a);
    Serial.print("  cm:");Serial.println(cm, 1);
  }
  for(int a=150; a>=30; a-=5){
    pan.write(a);
    delay(180);
    long us = pingUS();
    float cm = us ? us/58.0 : -1;
    Serial.print("A:");Serial.print(a);
    Serial.print("  cm:");Serial.println(cm, 1);
  }
}

Note: Adjust sweep limits (30–150°) to avoid cable strain and mechanical stops.

Use pigpio for stable servo pulses and precise echo timing. Level-shift HC-SR04 ECHO to 3.3 V.

Scan with pigpio

# sudo apt install pigpio python3-pigpio
# sudo systemctl start pigpiod
import time, pigpio

PIN_SERVO=18   # hardware PWM
PIN_TRIG=23
PIN_ECHO=24

pi = pigpio.pi()
pi.set_mode(PIN_TRIG, pigpio.OUTPUT)
pi.set_mode(PIN_ECHO, pigpio.INPUT)

def set_servo_deg(deg):
    deg = max(0, min(180, deg))
    us = int(500 + (deg/180.0)*2000)  # 500–2500 µs
    pi.set_servo_pulsewidth(PIN_SERVO, us)

def ping_us():
    pi.gpio_trigger(PIN_TRIG, 10, 1)
    t0 = time.time()
    while pi.read(PIN_ECHO)==0:
        if time.time()-t0>0.03: return 0
    start = time.time()
    while pi.read(PIN_ECHO)==1:
        if time.time()-start>0.03: return 0
    end = time.time()
    return (end-start)*1e6

try:
    for a in list(range(30,151,5)) + list(range(150,29,-5)):
        set_servo_deg(a); time.sleep(0.18)
        us = ping_us()
        cm = us/58.0 if us else -1
        print(f"A:{a}  cm:{cm:.1f}")
finally:
    pi.set_servo_pulsewidth(PIN_SERVO, 0); pi.stop()

• Power: Use a separate 5–6 V supply for the servo; tie grounds with the Pi.
• Cable relief: Leave slack at center; avoid twisting during sweeps.

ESP32 example (Arduino core). Level-shift HC-SR04 ECHO to 3.3 V. Power the servo from a separate 5–6 V rail; share GNDs.

ESP32: Pan + Ping Scan

#include <Arduino.h>

const int PIN_SERVO = 17;
const int PIN_TRIG  = 5;
const int PIN_ECHO  = 18;

const int CH = 0, FREQ = 50, RES = 16;
uint32_t degToDuty(int deg){
  deg = constrain(deg, 0, 180);
  float us = 500 + (deg/180.0f)*2000.0f;
  return (uint32_t)(us * FREQ * (1 << RES) / 1000000.0f);
}

long pingUS(){
  digitalWrite(PIN_TRIG, LOW); delayMicroseconds(3);
  digitalWrite(PIN_TRIG, HIGH); delayMicroseconds(10);
  digitalWrite(PIN_TRIG, LOW);
  return pulseIn(PIN_ECHO, HIGH, 30000UL);
}

void setup(){
  Serial.begin(115200);
  pinMode(PIN_TRIG, OUTPUT); pinMode(PIN_ECHO, INPUT);
  ledcSetup(CH, FREQ, RES); ledcAttachPin(PIN_SERVO, CH);
  ledcWrite(CH, degToDuty(90)); delay(500);
}
void loop(){
  for(int a=30;a<=150;a+=5){
    ledcWrite(CH, degToDuty(a)); delay(180);
    long us = pingUS(); float cm = us ? us/58.0f : -1;
    Serial.printf("A:%d  cm:%.1f\n", a, cm);
  }
  for(int a=150;a>=30;a-=5){
    ledcWrite(CH, degToDuty(a)); delay(180);
    long us = pingUS(); float cm = us ? us/58.0f : -1;
    Serial.printf("A:%d  cm:%.1f\n", a, cm);
  }
}

ESP-IDF: Use ledc PWM and rmt/capture for echo timing.

No driver is needed for the bracket itself. If you connect a USB-serial bridge for debugging:

• CH341 Driver (GitHub)

Arduino

• Arduino Project Hub
• Arduino Playground
• Arduino IDE Download
• Install Arduino Libraries

Raspberry Pi

• Raspberry Pi Projects
• GPIO Zero Docs
• Raspberry Pi Docs
• Raspberry Pi Software
• Pi Getting Started

Espressif

• ESP-IDF Programming Guide
• Espressif Technical Docs
• ESP-IDF GitHub
• PlatformIO + ESP-IDF
• Arduino Core for ESP32

Drivers / Other

• CH341 Driver (GitHub)

Note: Exact hole spacing and hardware may vary by batch; check your kit contents.

Important Notice For educational, prototype, experimental, laboratory and R&D use only. (non-RoHS)

WEEE

Not subject to WEEE marking; obligations apply to final equipment.

Manufacturer

Little Muffins Things Limited
166 River Heights, 90 High Street
London E15 2GQ
littlemuffinsthings.com

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