BLZphotos
BS2-Solenoid-Circuit-crop
The push button in the diagram is the manual water valve control for purging the line (momentary switch, normally open), otherwise the valve only opens when the microcontroller sends out a positive pulse on its output pin to activate the transistor switch and allow current to flow through the solenoid. A diode is placed across the solenoid power lines to prevent damage to the transistor from reverse voltage generated from the inductive load when the power is turned off. This recirculates it back into the solenoid coil instead of into the transistor.
BS2-Solenoid-Circuit-crop
The push button in the diagram is the manual water valve control for purging the line (momentary switch, normally open), otherwise the valve only opens when the microcontroller sends out a positive pulse on its output pin to activate the transistor switch and allow current to flow through the solenoid. A diode is placed across the solenoid power lines to prevent damage to the transistor from reverse voltage generated from the inductive load when the power is turned off. This recirculates it back into the solenoid coil instead of into the transistor.