Wireless Solenoid Control

Traditionally when using pneumatics, a technician is required to toggle a lever on a pneumatic valve. This poses a problem when the effect needs to be in a location that a technician cannot. One solution would be to operate the actuator remotely by running air tubing from the actuator all the way off stage to the valve. While this may be an option for a stationary unit, running air tubing to a rolling unit from offstage is not a viable option. The next option would be to use electronic solenoid valves and implement wireless control. The following describes how to build such a system.

At the heart of the system is an Arduino Ethernet, which is an easy to use microcontroller board. The PC communicates wirelessly with the Arduino through the use of a WiFi router. When the operator clicks a button on the computer screen, the corresponding solenoid is switched resulting in the actuation of a pneumatic cylinder.

The entire system can be easily sourced from internet retailers for less than $150 (table 1). Once constructed, the system can be an off the shelf solution for future shows. Most solenoid valves operate at 24VDC so either two 12V batteries in series or a 24V AC adapter is required. The 12V DC-DC converter from Automation Direct is only necessary if you choose to run the system on battery power. The DC-DC converter is used to provide the wireless router that connects to the Arduino with regulated power for smooth operation. Alternatively, you can source everything except for the DC-DC converter from your local Radioshack for a slightly higher price.

There are a number of optional items that can be incorporated into this project to make it a more durable and professional looking piece of hardware. I used a 7”x5”x3” ABS plastic enclosure from Radioshack to protect the electronics (figure 3). I also used a removable screw terminal header for the solenoid and power connections.

The software package that I developed for this project contains two parts and can be downloaded from rybitski.com. These files are provided free of charge for non-commercial use. The first part is the firmware for the Arduino and the second part is a visual basic GUI program for Windows. The Arduino Ethernet does not have a built in USB host so a USB Serial Light Adapter is required to upload the program to the board. Depending on where you purchase your Arduino from, the USB adapter may not be included. This is an inexpensive adapter made by Arduino that can be sourced from Amazon for $15. To start construction – grab a soldering iron, resistors, diodes, Darlington transistors (TIP 120), and PC board.

• Follow the pseudo-schematic in figure 1 for the connections. It is important to note the orientation of the diodes as these are directional components. The diodes are used to prevent surges in voltage produced by the switching on and off of the solenoid coil from damaging the transistors (figure 2).

• The Arduino requires an input of 7-12VDC to the “Vin” pin to operate; this is a separate requirement from the 24VDC that the solenoids need. Pay careful attention to your power connection; if you mix it up you may overpower the Arduino and have to purchase a new one.

• If you choose to use the DC-DC converter (figure 4), take the 12V from that and connect it to the Arduino, otherwise you will need a power adapter.

• Using the Arduino IDE, upload “solenoid_control.ino” to your Arduino Ethernet.

• Open and install “PC_control.exe” which is located in the software package. This program runs on Windows XP or higher and requires a wireless card to operate.

• Make sure that your Arduino and router are powered up and running.

• Using the wireless connection manager within Windows, connect to the wireless router that is connected to your Arduino. Note that Windows may say “no internet” once you connect; this is normal and not a concern.

• Click the connect button within the Solenoid Control program and then click any of the effect buttons to ensure everything is working properly.

A challenge that was presented for PCPA’s 2013 production of Mary Poppins was the moving effects of the kitchen scene. The idea was to power the effects with pneumatic actuators. This posed a problem since the multipurpose unit had to be rolled on and off stage. To solve this problem, the wireless computer controlled system was developed allowing an operator to easily navigate and control the system with the click of a mouse. Wireless control of pneumatic effects is a challenge that is presented for many shows. This relatively low cost and easy to use device proved to be reliable and versatile. During PCPA’s 49 performance run of Mary Poppins, there were no issues with the solenoid controller. Unlike most devices created specifically for a show, this one can be used for future productions.

 

Solenoid Control Software