MiCroController-baSed autoMatiC FluSh SySteM
UMAR SUNIL K
n manual flush systems, the user presses a button, which opens a flush valve allowing mains-pressure water to flow into the bowl, or sometimes the user presses directly a flush lever (a handle connected to a flushometer). The valve contains a pneumatic mechanism that closes it afterapresettime. Today, manual flush system has been replaced with a sensor-operated system that automatically flushes the fixturewhentheuserdeparts. The microcontroller-based automaticflushsystempresentedhereuses aninfraredsensortodetectauserapproachingthefixture,thenitwaitsunParts List Semiconductor:
Resistors (all ¼-watt, ±5% carbon):
IC1 IC2 IC3 T1 IRX1 D1-D5 LED1-LED5 IRLED1, IRLED2 R1,R11-R14 R2 R3-R8 R9 R10 R15 Capacitors:
- 7805,5Vregulator - AT89C2051 microcontroller - CD4050hexnon invertingbuffer - BC548npntransistor - TSOP1738IRreceiver module - 1N4007rectifierdiode – 5mmLED – IRLED
Fig. 1: Installation of the automatic flush system
- 330-ohm - 220-ohm - 10-kilo-ohm - 4.7-kilo-ohm - 150-ohm - 1.2-kilo-ohm - 1000µF,25Velectrolytic - 10µF,16Velectrolytic - 22pFceramicdisk - 230VACprimaryto 7.5V,300mAsecondary transformer - 6V,1C/Orelay - On/offswitch - Push-to-onswitch - 6Vbattery - Solenoid(operated with6V)
C1 C2,C3 C4,C5 X1 RL1 S1,S2 S3 BATT.
tiltheuserdeparts.Asolenoidisused to actuate the flush from a 6V power supplywithbatterybackupinsidethe unitthatalsopowersthesensorcircuit. Thisflushsystemisfullycontrolledby amicrocontroller.Italsoflushesbefore the person departs if the person is presentformorethanthepresettime (5minutes). Installationofthismicrocontrollerbasedautomaticflushsystemisshown inFig.1.TheIRtransmitterLEDand the IR receiver modules are mounted side by side such that when the user approaches the mechanism, the IR receivermodulereceivestheIRsignal reflected off the person. A solenoid operated water valve is used in the system.
Fig. 2 shows the circuit of the microcontroller-based flush control system.
It is built around Atmel 89C2051 microcontrollerthatcontrolstheprocess ofautomaticallyflushingthetoilet. The AT89C2051 is an 8-bit microcontroller with 2 kB of flash-based program memory, 128 bytes of RAM, 15 input/output lines, two 16-bit timers/counters, on-chip oscillator and clock circuitry. A 6MHz crystal is used for providing clock. Port pins P1.0 through P1.4 of the microcontrollerareconnectedtobuffersN1 throughN5ofCD4050via10-kilo-ohm pull-upresistors,respectively. All the input/output (I/O) pins are reset to ‘1’ as soon as RST (pin 9) goes high on pressing switch S3. Holding the RST pin high for two machine cycles while the oscillator is running resets the device. Power-onreset is achieved by capacitor C2 and resistorR9. Pin12(P1.0)ofmicrocontrollerIC2 w w w. e f y m ag . co m
6 8 • d e c e m b e r 2 0 0 6 • e l e c t ro n i c s f o r yo u
provides the 38kHz c l o c k f r e q u e n c y , whichisbufferedby N1 to drive the two parallel IR-LEDs. These IR-LEDs act astheinfraredsignal transmitter. Resistor R10 limits the current through the LEDs.PortpinsP1.1, P1.2, P1.3 and P1.4 are used for indicationofstandby,alert, active and flush, respectively. Port pin P1.4alsodrivesrelay RL1throughtransistorT1.DiodeD5acts as a free-wheeling diode. The solenoid coil operated off 6V is connected to the...