Sensors
HC-SR04 Ultrasonic Distance Sensor
৳140
Measures distance from 2 cm to about 400 cm by timing an ultrasonic echo, with roughly 3 mm resolution. The standard obstacle sensor.
Send a 10 microsecond pulse on the trigger pin, then measure how long the echo pin stays high — the round-trip time converts directly to distance. Works in complete darkness, which is where infrared sensors fail.
What you can build
- Obstacle avoidance for robots
- Car parking assistants and reversing alarms
- Water tank level measurement from above the surface
Not sure it will work? Test your circuit free in Tekko Sim — on your phone, in Bangla or English.
| Category | Sensors |
| Model no. | HC-SR04 |
| Availability | In stock |
| In stock | 10 pcs |
| Delivery | Cash on Delivery, nationwide Bangladesh |
| Measuring Range | 2–400 cm |
| Resolution | roughly 3 mm |
| Operating Voltage | 5V DC |
| Operating Current | about 15 mA |
| Ultrasonic Frequency | 40 kHz |
| Measuring Angle | roughly 15 degrees |
| Trigger Input | 10 microsecond TTL pulse |
Questions about the HC-SR04 Ultrasonic Distance Sensor
How do I read the HC-SR04 in Arduino code?
Send a 10 microsecond HIGH pulse on the trigger pin, then use pulseIn on the echo pin to measure how long it stays high. Distance in centimetres is that time in microseconds divided by 58, because sound covers the round trip at roughly 58 microseconds per centimetre.
Why do I get random or zero readings?
Usually the target. Soft, angled or very small surfaces scatter the pulse instead of reflecting it back. The sensor also needs a short gap between readings — poll it no faster than about every 60 milliseconds — and it cannot measure closer than 2 cm.
Does it work with a 3.3V ESP32?
Power it from 5V, but the echo pin outputs 5V and must not go straight into an ESP32 GPIO. Drop it with a two-resistor divider first.
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