Electronic Hose Timer

Overview

An electronic hose timer screws onto a garden spigot (faucet) and gates water to the downstream hose on an automatic schedule. The simplest models are battery-powered timers that open a Solenoid Valve Assembly at a set time each day for a set duration, then close the valve to cut water flow. More advanced units offer multiple on/off schedules per day, weekday/weekend differentiation, and interval-based watering (e.g., 10 minutes of watering every 8 hours). The operator enters the program once at setup, and the timer remembers it via battery-backed memory.

This is useful for properties where the owner is away, for vegetable gardens that require frequent shallow watering, and for holiday-home irrigation. A single timer costs USD 25–60 and saves electricity (no pump) and manual labour (no hand-watering).

How it works

The 4 AA batteries in the Battery Holder are wired in series, producing nominally 6 V DC (4.5–6.0 V depending on cell chemistry and remaining charge). A Voltage Regulator steps this down to a stable 5 V for logic and 6 V for the solenoid coil.

The Real-Time Clock, a battery-backed real-time clock IC (e.g., DS3231), keeps accurate time even when the timer is powered off (as long as a backup cell is present). The Microcontroller, typically an 8-bit or 16-bit ARM Cortex-M microcontroller, reads time and date from the RTC and compares them against user-programmed schedule entries stored in non-volatile flash memory.

The operator uses the Control Keypad (usually 3–6 tactile buttons) to navigate a menu displayed on the LCD Display. They set the day of the week, start time, duration, and frequency (once daily, multiple times, or interval). When the microcontroller detects that current time matches a scheduled start time, it energizes the Relay (or directly switches the Solenoid Coil on low-power designs), applying 6 V to the solenoid's electromagnetic coil.

The magnetic field pulls the Solenoid Plunger upward, which presses against the Poppet Spring, compressing it and lifting the poppet valve seat inside the Valve Body. Water pressure from the spigot immediately flows through the opened valve and out the Outlet Fitting to the connected hose.

The microcontroller counts elapsed time using its internal timer. When the programmed duration expires (e.g., 15 minutes), the software de-energizes the relay, cutting power to the solenoid coil. The magnetic field collapses, the Poppet Spring pushes the plunger down, and the poppet reseats against the valve body, shutting off water flow. The timer then waits for the next scheduled start time.

An Inlet Screen Filter blocks sediment and debris from entering the valve, protecting the solenoid needle and poppet seat from jamming. The screen must be rinsed or replaced periodically (typically annually) if water quality is poor.

Battery life is typically 6–12 months. The high-efficiency microcontroller and intermittent solenoid duty cycle (the solenoid is only powered during the on duration, not continuously) keep current draw very low, typically 10–50 mA when running, and nearly zero when in sleep/standby mode waiting for the next schedule trigger. When batteries are depleted, the timer loses time and stops switching. Replacement is straightforward: the user pops open the battery door, swaps in four fresh AAs, re-enters the weekly schedule, and the timer is ready to operate for another year.