As we've written in our recent Essentials of Machine HMI reporting, the foundational component of any machine automation solution is the human-machine interface (HMI). Local HMIs range widely in sophistication — and price — depending primarily on how much interaction and information exchange is required between the human operator and the machine itself.
A relatively simple, unconnected machine might need only a few hardwired lights and pushbuttons. At the other end of the spectrum, a fully functional industrially hardened PC could be required. In between these two extremes, we find a range of microprocessor-based operator panels or operator interface terminals (OITs) that provide a configurable graphical operator display and interface in a more compact, less expensive package than a typical industrial PC. In short, the need for increased application flexibility and the need to handle more complex information management tasks will typically drive the machine designer to more capable solutions.
In a recent Control Design audience study on HMI and related components, we learned that 65% of respondents indicated the operator interface hardware installed on their machines was a graphical display with touchscreen. That was followed by graphical display with keyboard or other input device (21%), then text-based display with integral input keys (4%), and discrete panel switches and lights only (1%).
For all but the simplest of applications, increased functional and performance requirements drive machine OEMs away from simple status indicator lights and toward increasingly sophisticated HMIs equipped with graphical displays. On the human input side, with the exception of a few critical buttons (for emergency machine shutdown, for example) discrete switches, too, give way to configurable input keys which, in turn, are yielding to integrated touchscreens.
Nevertheless, on many levels, there's a need for discrete input devices, as this roundup demonstrates.
|Less Is More
A3U 22 mm, flat-surface, pushbutton switches have a ribbon-cable connector for less assembly, less wiring and less chance of errors. 50 mm body length reduces board height to save space under a panel. There are lighted and non-lighted pushbutton versions with a range of pushbutton colors.
Omron Automation and Safety
|Sweet Little 16
LB series of 16 mm miniature switches include illuminated selectors, lever selectors, dome pilot lights, lever switches and buzzer models. Illuminated selectors and dome pilot lights are available in green, red, white, amber, yellow and blue. The switches have a 5 A operating current and are available with a choice of SPDT, DPDT and 3PDT contact. All provide an IP65 degree of protection.
Turn to Safety
|Installation a Snap
OMPBD7 22-mm pilot devices offer modular assembly and interchangeability. A toolless mounting latch mates the front element with the contact blocks and other back-of-panel components. The mounting latch is available in a plastic and metal design. The latches install with a click and are removed by pushing a rotating collar to the right.
40-mm emergency stop buttons mount to flat surfaces without disassembling or individual wiring. They come with a non-illuminated base in four styles: standard, illuminated actuator; lockable actuator and an illuminated lockable actuator; or in an illuminated base with a standard or a lockable actuator. Push-to-stop, twist-to-release or pull-to-release actuator and direct (positive) opening operation is compliant with ANSI B11.19, ANSI NFPA79, ISO 13850 and IEC/EN 60204-1.
|Rock On, Rock Off
789 Series DIN-rail mount switch modules are 17.5 mm wide with rocker switches. 789-800 provides automatic and hand modes to switch a device/machine between PLC-driven operation and manual mode for troubleshooting, etc. 789-801 on/off rocker switch lets users manually control typical accessories within a control cabinet.
|See More Lights
SW44895 quad lamp, pushbutton SPST to DPDT switch assembly options include rubber dust boot for panel protection and enlarged lens cap to match industry standard sizes. Performance specifications include life capability of 100,000 minimum actuations. Ratings are 2.0 A resistive, 0.5 A inductive.
Without a Wire
Switches and More
|See the Buzz
With polycarbonate/ABS housings, 22.5-mm panel-mount continuous-tone, electrical buzzers have LED indicators with red or yellow lenses. Two-wire, high-intensity LED 29-mm diameter beacons are available in panel-mount styles, or on a M20 threaded base for use with limit and cable-operated switches.
|Light ‘em Up
LP6US LED surface-mount lights in blue, red, yellow and clear have six LEDs with 33 flash patterns for use in environments -40 to 149 °F. Up to four lights can be synchronized to form a larger warning system. These lights are rated for 10-30 Vdc operation, and are CA Title 13 compliant and SAE J595 certified.
You Light Up My Panel
|Marks the Spot
MetalliCard metal markers labeling system provides an in-house print capability on aluminum or stainless-steel marker plates for pushbutton and control panel identification. Installation options include self-adhesive, riveted markers, attached with plate holders. Pushbutton holders work with 22 mm pushbuttons from various manufacturers.
Preassembled and ready to install or assembled-to-order control stations include a heavy-duty, cast aluminum enclosure that's assembled with 22 or 30 mm pushbuttons. Use up to two contact blocks with the illuminated operators or up to four contact blocks with the non-illuminated operators. This enclosure can be modified to accept any non-illuminated 30 mm operator or pilot light as well.
|C the Light
C22 pushbutton family has operator and contact blocks together in one housing. The 22-mm design provides the same pressable area as 30 mm buttons. It includes LED illuminated pushbuttons and pilot lights, twist-to-release emergency stops, selector switches, and comes in flat and extended non-illuminated versions.
E-Box low-profile housing for single control components at detached or remote locations includes bottom and top parts, contact module with contact block, and an e-stop actuator. Choose gold contacts for 35 V, and 100 mA maximum or silver for 250 V and 4 A maximum, which is available with two normally closed contacts, or one normally closed and one normally open.
RafiX 22 FS+ products include illuminable pushbuttons with a protruding or flat baffle, selection/key/mushroom-type pushbutton switches, and e-stop buttons, signal indicators, potentiometer actuators and USB feedthrough. All actuation products have IP65 or higher rating.
Signaling solutions for machinery control panels include Series P22D LED pilot light, choice of continuous On or 1 Hz blinking. It installs in standard 22.5-mm cutouts, and has a width of 1.1 in. outside diameter. Lens colors include white, amber, red, blue, green, in voltages of 12, 24, 115 or 230 Vac/dc.