Pilot devices are at the center of the human-machine interface in an industrial environment. Pilot devices primarily consist of pushbuttons, selector switches, and indicating lights. They can be used in nearly any application but are most commonly used in commercial and industrial applications due to price, appearance, and heavy-duty construction. When an operator needs to check the status or make some changes to industrial equipment, it is very common to use a pilot device.
NEMA vs IEC
NEMA pilot devices are typically installed in a 30mm punchout hole, so they are frequently called 30mm pilot devices. They are typically supplied pre-assembled with the contacts already attached, though the contact configurations can generally be changed in the field if you need different contacts.
IEC pilot devices are typically installed in a 22mm punchout hole and are commonly referred to as 22mm pilot devices. They are much more commonly sold modularly, where you can buy the operator separately from the contacts. Springer Controls offers them separately or with the contacts included, depending on your preference.
Contacts are usually not interchangeable between product lines, so it is important to ensure you get the right contacts for your pilot device. Springer Controls can help to ensure you are getting the right parts.
Pushbuttons
Pushbuttons are used in so many applications it would be impossible to describe them all. Pressing the button causes the state of the contacts to change. A Normally Open contact would close allowing electricity to flow through while the button is pressed…or a normally closed contact would open, stopping the flow of electricity through the contact. Pushbuttons can be fitted with multiple contacts to perform a variety of functions.
Flush (left) and Extended (right) Pushbuttons
Pushbuttons have different styles to make the buttons easier to identify and make it easier or more difficult for the operator to press the button. Easier to press makes it safer in emergency situations, while more difficult to press helps to prevent accidental operation
Flush buttons require more precise finger placement, while extended buttons are easier to press.
Color coding helps the operator quickly identify the button’s function. Buttons can also be illuminated to provide backlighting for darker environments.
Most industrial buttons are MOMENTARY in operation, meaning that the contacts are only switched when the operator presses the button. When the button is released, it pops back out via a spring, and the contacts return to their normal state (normally open or closed). Maintained buttons are available but generally used for special purposes because it can be difficult for an operator to look at a maintained button and determine if it is pressed.
Mushroom Head Push Buttons
Mushroom head push buttons are designed to be easy for the operator to press. They often have larger heads and no bezel, so they can be activated by the whole hand instead of just a finger. For this reason, they are very commonly used for emergency stop buttons. While some mushroom push buttons have momentary operation, it is much more common for these to be maintained. This means that the operator must take another action to “un-press” or reset the button position once pressed. It could be a twist (twist release) or require the operator to pull the button out (push-pull). Some may even require a key to release. This is because if there is an emergency situation, you may want some control over who can reset the button.
Twist Release (left) and Key Release (right) Pushbuttons
Selector Switches
Selector switches are rotated instead of pressing like a pushbutton. The rotating piece has raised portions that activate the contacts. Selector switches can provide a range of benefits, including:
- Can have multiple positions (2, 3, 4 and 5 positions) to perform several functions in the same space as a pushbutton
- Operator can visually see what position the switch is in
- Cams / Plungers can selectively activate the contacts differently to perform different functions
The photos below show two different types of selector switch handles…knob versus lever.
Knob (left) and Lever (right) Selector Switch Handles
Pilot Lights
Pilot lights are simple indicator lights. If a machine is operating, a green light can indicate that it is on. A green light can also indicate an area is safe for an operator to enter. Red lights can indicate warnings or faults. Yellow, blue, or white lights can indicate a variety of functions. With a push button or selector switch, the voltage is unimportant as the contacts are typically rated for higher voltage than you would typically apply anyway. We have to power an LED with a pilot light, which could require a specific voltage or a tight voltage range. Typically, 24V, 120V, or 240V, but other options are available. Specifying the voltage you will supply when specifying a pilot light is important.
Pilot Lights
Double Pushbubttons
There are double pushbuttons available for common opposable functions like On/Off or Start/Stop. These provide 2 buttons (and can even add a small pilot light) into a single 22mm punchout, saving assembly time and space on the control panel. These will typically require 2 contacts, usually a normally open contact for On and a normally closed contact for Off.
Double Pushbuttons
This is just an overview of the wide range of pilot devices available for interfacing with electrical controls. Contact Springer Controls for more details and assistance in selecting the right pilot device for your requirements.