PMI Design Guide for EngineersThe Ultimate Resource for Panel Mount Indicators
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Panel Mount Indicator Design Guide
Status indicators are all around us in everyday life. So much that the average person — or even a seasoned engineer — may not appreciate how much we rely on status indicators every day. The operation status of a device can be communicated using light pipes, panel mount indicators (PMIs), capacitive touch buttons, or some other form of light. And in many cases, the light is combined with icons or text to enhance the user experience.
It’s not all about looks and cool, sleek interfaces, either. The European Union’s equivalent of OSHA cited HMI design as an emerging risk due to the increased dependence on technology in the workplace. Translation: HMI design has the power to influence safety and outcomes. Effective status indication can:
- Enhance the end-user experience
- Prevent workplace accidents
- Improve operator reaction times
- Provide reliable indication for years
Fortunately, human-machine interfaces and control panels can be designed for optimal indication, whether they use PMIs, light pipes, or other illuminated communication signals.
This guide covers the key decisions designers and engineers must make to ensure their interfaces use the appropriate PMIs for the job. Whether you’ve been working with panel mount indicators for one year or 20, here’s a handy resource to help ensure you make informed indicator decisions early on in the design process. The sooner the right PMI is specified, the fewer compromises will need to be made later when the design is set and tooling is completed.
Common questions about panel mount indicator
What’s a Panel Mount Indicator (PMI)?
A panel mount indicator is a type of status indicator attached directly to a device’s operator panel rather than the machine’s inner workings. A panel mount indicator may also be known as a:
- Pilot light
- Indicator light
- Status indicator
Panel mount indicators go above and beyond communicating on or off status. These indicators are used in many industries to communicate operating and warning status to end-users. They can be powered with a range of lighting technologies — from LED panel mount indicators to neon or even incandescent PMIs.
Which industries use PMIs?
The short answer is, almost all of them. While you may think about the pilot light on your coffee maker or a power button on a conveyor belt at a warehouse, PMIs are used in devices of all sizes and industries, including:
Food and Beverage
What do PMIs look like?
While PMIs can be customized in many ways to suit the application and the industry, they are all typically made up of:
PMIs can range from 2V up to 250VAC, depending on the application and design requirements.
how is the PMI connected to the power source? Wire leads, screw terminals, solder terminals, or tabs that conduct electricity are used, depending on the design.
the plastic or metal piece of the indicator that encases the lamp.
the bulb used in the PMI, whether LED, incandescent, or neon.
the color of the lamp itself. Standard colors are yellow, red, blue, green, white and orange, with amber and violet options available in some indicators. Panel mount indicators can also be bi-color or tri-color.
the lens can come in various shapes and colors to provide the desired aesthetics and viewing angle for proper operation.
- Dome – lens is rounded at the top and provides the widest viewing angle
- High-dome – lens extends prominently above the control panel and is rounded at the top
- Semi-dome – mid-range viewing angle compared to dome or flat
- Flat – flush with the panel for more targeted light
- Hi-hat – lens extends well beyond the surface of the HMI while maintaining a flat shape
a bezel is an optional ring or sleeve that encases the lamp. Using a bezel can be purely aesthetic, or increase contrast between the bezel and LED to improve visibility. Bezels can also add a layer of protection from dust and moisture. Bezels are typically made of plastic or stainless steel and available in multiple finishes, styles, and colors.
Bezel color will be dictated by the type of material used. Common colors are:
- White – plastic or metal PMIs
- Black – plastic or metal PMIs
- Silver – stainless / aluminum PMIs only
like the name implies, a movable “snap” allows the PMI to be easily assembled to the panel without any additional tools or hardware.
Snap-fit with D mounting
a D-shaped mounting hole on the panel helps secure the snap-fit PMI to prevent rotation that could impact performance due to vibration. This option is easy to install without additional hardware.
the PMI is secured with the help of friction as the LED housing and panel are pressed together. The interference allowance will determine the tightness of the seal.
What’s the difference between a panel mount indicator and a light pipe?
How much does a PMI typically cost?
- Materials used
- Working environment / moisture protection
- Device design
- Number of indicators used
- Lens type
- Power needed
- Terminal type
- Additional hardware
On average, engineers can expect to pay $1 to $6 per unit for a very basic PMI. On the other hand, those with additional features or customization can run $20 each or more. Consulting with an experienced team of experts can help you compare several options to find the ideal solution for your needs and budget.
Benefits of Using Panel Mount Indicators
Several standard options available to meet most needs
Easy to customize
Cost-effective installation + assembly
Reliable, uniform illumination
Lighting Technology Used in PMIs
Average Operating Life
- Incandescent – 1,500 Hours 3% 3%
- Neon – 25,000 Hours 25% 25%
- LED – 100,000 Hours 100% 100%
LED PMI Retrofits Deliver a Win-Win
Manual electric motor starter
- Up to 50% savings in energy consumption
- An LED lamp that lasts 4x longer than its neon predecessor
- Streamlined production with snap-fit design
- High visibility for enhanced operator safety
- Upgrading an existing motor starter unit with a custom PMI instead of a new product design
- Significant energy savings
- Switching to wire leads instead of tabbed terminals that kept breaking during high-vibration environment
- Elimination of maintenance and warranty claims from tabbed terminal
- Fast, tool-free assembly
What to Consider When Choosing a PMI
Moisture and Dust Protection
Operating and Storage Temperatures
- Hexnuts or additional hardware to help secure the device in place
- Threaded housing
- D mounting hole prevents rotation
- Lens shape
- Lens texture
- Lamp intensity
Think only industrial applications use PMIs? Think again. Panel mount indicators can be found in a range of industries, including:
we modified our 1092 Series to create a high-voltage PMI (250V) to help one commercial grill manufacturer save on production costs by eliminating the need for an additional 12V power converter.
- Put yourself in the user’s shoes
- Conduct usability testing
- Keep it as simple as possible
- Factor in human error
Learn more about designing for the user experience (UX) here.
- Simplicity: Intuitive operation drives safe operation
- Design footprint: How many indicators are needed? How much room do you have? What’s the budget?
- Branding/aesthetics: Should the colors complement the established brand?
- Working environment:
- User experience: Will the operator be standing across the room? Seated? How will they use the device in the real world?
- Operator knowledge: There’s a good chance some of the other machines an operator would use already exist with visual vocabulary your end-users already understand. Or, there may be other colors they have already gotten used to, such as the colors of a traffic light. Common examples include:
Separate PMIs for Every Function
One Indicator, Multiple Colors
One Indicator, Multiple Functions
- Pulsing blue (slow) – during set up, while the device is connecting to Bluetooth
- Blinking blue (fast) – while the app is open near the Whistle tracker or during a family trip, transferring data via Bluetooth
- Blinking red or amber/orange – tracker’s battery is very low and needs to be charged
- Solid amber/orange – tracker is charging
- Solid green – tracker is fully charged
- Blinking green – tracker is updating location (during Track or Locate)