ELECTRONIC CIRCUIT

The spool valve acts only at 230V AC. But the controlling of various valves is done with the help of the microprocessor which output only the 5V DC. The 5V DC is connected to the 230V AC supply with the help of electronic circuit.

The electronic circuit consists of
    1. Transistor ( SL 100 )
    2. Relay ( 12V )
    3. Diode ( 1n 4007 )
    4. 12V DC power supply
    5. 230V AC power supply
        
In the electronic circuit common emitter mode NPN transistor used. The collector is connected to the  +12V power supply through the solenoid coil A, B of relay R4 (i.e.) connected in series with transistor. The emitter is connected to common ground. In the switch part of relay is connected to the phase of 230V AC and D is connected to one wire of the valve and the other wire is connected to neutral of AC power supply.

WORKING

        The input is given to the base of the transistor through the 1k resistors. when a voltage is applied to the base the transistor, the conventional current flow from the collector to emitter via the solenoid coil of the relay, the coil get magnetized and make the switch CD to get contact ( that is switch is on ). So the AC 230V flows through the solenoid coil of valve and the direction of the flow of air is get changed in other direction, which is connected to the cylinder. So whenever the voltage is given to the base of the transistor there is flow in current to the valve and the direction of flow of air is get changed.

ELECTRONIC CIRCUIT