Automatic Soap Dispenser

Overview

An automatic soap dispenser detects a hand placed beneath its infrared sensor and pumps a measured dose of soap or hand sanitizer without contact, a hygienic and convenient solution widely installed in public restrooms, restaurants, hospitals, and schools. The device eliminates the germs spread by touching a soap dispenser pump handle shared with hundreds of people daily. The core is a sensitive Infrared Sensor Module with an infrared LED and phototransistor that detect the presence of a hand, triggering a Pump Motor and Pump Head to deliver a precise 0.5–1.2 mL squirt. Battery-powered and refillable, each unit serves 20–50 people per refill cycle, depending on traffic.

The Housing Assembly is a compact wall-mount case with the sensor window at the top and a soap nozzle at the bottom. The Infrared Sensor Module emits a 950 nm infrared light and waits for reflection; when a hand appears within 10–20 cm, the reflected light triggers the Control Board, which energizes the Pump Motor. The motor is a small 3–6V DC unit geared down to ~60–100 RPM, driving a Pump Head with a peristaltic action. Peristaltic pumping works by sequentially squeezing flexible tubing to create a one-way flow: as the rotor lobe moves around, it pinches the inlet tubing first (drawing from the Soap Reservoir), then the outlet tubing (pushing liquid out), creating a precise volumetric pump with no moving seals. A Solenoid Check Valve integrated check valve prevents backflow. The Battery Pack holds four AA cells (6V), powering the motor and sensor amplifier for weeks or months before replacement.

How it works

A user approaches the sink and places their wet or dry hand directly below the dispenser within the 10–20 cm detection zone. The infrared emitter beams out a steady 950 nm signal, and the receiver measures the reflection strength. If the reflection is above the threshold (indicating a hand), the Control Board microcontroller pulses the Pump Motor for ~500 ms. The motor drives the peristaltic rotor, which compresses the inlet tube (drawing soap from the tank), then the rotor continues and compresses the outlet tube (pushing the soap out the nozzle into the user's palm). One motor pulse delivers ~1 mL of soap, enough for a full hand wash. The user rubs their hands together under the sensor; a typical hand-washing takes 15–20 seconds, and the dispenser will trigger 1–2 more times if the user places their hands back under the sensor. At the end of the wash, the user moves away and the dispenser stands ready for the next person. When the tank runs low (often indicated by a visual float window on the side), a facility manager removes the refill cartridge and snaps in a fresh 400–1,000 mL bottle of soap or sanitizer, a 10-second swap. Advanced models include foam pumps for gel hand sanitizers, adjustable dose volume (for cost control), and sensor sensitivity tuning. Battery life is typically 3–6 months at moderate traffic (50–100 activations/day), making these highly economical for high-traffic facilities.