Pick and Place – SOLENOID VALVE DESIGN AND CONTROL

By: Tyler Jones (Manufacturing) and Kevin Ruelas (Electronics)

The above Figure 1 and Figure 2 schematics show the solenoid circuit simulated in LTSpice. The circuit on the left shows that when the arduino pin is set to high the circuit turns on allowing the current to flow through drain and source to the solenoid valve. The circuit on the right shows that when the arduino is set to low, there is no current flowing through the drain and source to the solenoid.

This creates an electronically controlled switch, and can be programmed to turn the pump on when picking a part, and off when placing a part. This is vital to the pick and place control system because it needs to be able to switch on using power from the Me Adapter board of +5V, to control a larger voltage of +11.7V from the Me Uno header pins. The IRF 530 MOSFET switches the gate voltage of +4.7V to the source drain voltage of +11.7V This voltage can is now large enough to drive a current to the solenoid and turn it on and off.n The diode is placed from power across to the solenoid as a flyback diode. This means that the cathode points toward the positive power rail. The diode is a 1N4001 1 amp diode. The sole purpose of the flyback diode is to prevent the unwanted voltage spike that can be created in the inductive solenoid coil. The IRF 530 MOSFET was chosen based on the datasheet values that it can handle lower logic level voltages to turn on, and can channel about 20V across the source drain channel. This is more than enough to handle our 12V source drain voltage The +4.7V control voltage from the arduino is programmed to correspond to the following values.

CODE SENT	$9 (GCODE)	$10 (GCODE)
ARDUINO PIN	+4.7V (HIGH)	+0V (LOW)
IRF 530 MOSFET	ON	OFF
SOLENOID	ON	OFF
SUCTION PUMP	ON	OFF
ACTION	PICK	PLACE

 The solenoid was tested using an ammeter in series with the Drain of the MOSFET and wire of the solenoid. The current draw shown in Figure 3 through the MOSFET into the load was about 410mA. The turn on current needed to excite the coil in the solenoid was found to be about 310mA. This means that the solenoids resistance value can be modeled most accurately as an inductive coil load in series with a resistive load. The total resistance of the solenoid based on current draw was an operating range of about 24-35 ohms. The circuit works as designed and tested.

The tested circuit shown above was translated into a custom soldered PCB, in order to have the wires and components secured to a fixed location within the electronics housing. The PCB board will be mounted on standoffs inside the electronics housing.