Simple Liquid Dispenser For Bottling Plants

The Simple Liquid Dispenser operates through an integrated analog and digital control system designed around the ATtiny85A microcontroller. Power management begins at the input terminals, where a 7805 5V voltage regulator (IC1) steps down an external power supply to provide a stable 5-volt rail for the low-voltage logic circuitry, supported by necessary filtering capacitors. The ATtiny85 microcontroller monitors user inputs from push buttons (S1 and S2) to initiate dispensing cycles and provides visual feedback using a common-cathode bi-colour LED (BICO1) to indicate system states. To measure the dispensed liquid, the system relies on a YF-S201 liquid flow sensor, which outputs pulses proportional to the volume of liquid passing through it. Once the microcontroller counts the correct number of pulses corresponding to a precise volume, it alters its output state. Because the ATtiny85's output pins cannot directly drive high-power inductive loads, the control signal is sent to a BD139 NPN transistor (T1). This transistor acts as a solid-state switch to control the normally-closed solenoid valve, opening the valve to let liquid flow and closing it immediately when the target volume is reached.