Making Sense Volume 1

8/11/2019 Making Sense Volume 1

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Making SenseVolume 1 – Insight for Engineers



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Table of Contents

Top Three Reed Switch No-No’s

3

Specifications versus Applications

4

Reed Switch Customization

5

Wisdom from the Design Journey

6

A New Solution to an Old Application

8

Making Sense Author Profiles

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Top Three Reed Switch No-No’sAuthor: Lawrence McClure

The reed switch: A simple electro‐mechanical device with a contact

area and two to three leads that, when the correct magnetic or

electrical force is applied, facilitates continuity through the switch.

Although simple in nature and application, we engineers sometimes

can get a little creative when it comes to the correct application of this device. Below are three

common “no‐no’s” that can help you get the best performance out of your reed switch.

No‐No #1: Treating a reed switch like a resistor

Whenever the reed switch leads are manipulated in any way, it can affect the magnetic properties of

the switch. For example, you cannot bend or cut the leads and expect to get the same magnetic

properties of the switch as when the leads are straight or at standard length. The switch is designed

with specific properties. It is recommended that any custom modifications, such as bending or cutting,

be done by the manufacturer, who can make sure that the resultant magnetic effect is understood

and that the hermeticity is maintained in the process.

No‐No #2: Dropping the reed switch or smacking it on a table

As obvious as it may sound, dropping the reed switch or even banging it up against a table‐‐as we’re

tempted to do when the switch is not operating as expected‐‐is not a very good idea. Due to the

properties within

the

hermetic

seal,

the

internal

workings

of

the

switch

are

highly

sensitive,

especially

in the smaller switches. If the switch does not work, replace it. Don’t break it.

No‐No #3: Overloading the reed switch

Again, it may seem self ‐evident, yet it occurs from time to time that a switch specified to a certain

load is pushed a little too far over the edge. The electrical specifications on the switch have been

tested and approved so for instance, loading a 250‐mA switch with 3 amps might not provide the

results that you are looking for.

I hope

these

fundamental

facts

about

reed

switch

application

will

prove

to

help

you

in

future

projects

and potentially save a lot of time on R&D and troubleshooting.

For more information about Reed Switch Basics, check out our Application Notes. Or, if you have other

questions about reed switch functionality, just ask. We’re here to help!



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Specifications versus ApplicationsAuthor: Zack McGillIt is challenging to create a general specification sheet for a product that exhibits application‐

dependent performance.

HSI

spec

sheets

are

meant

to

provide

users

with

useful

information

about

the expected performance of standard products. In most cases our reed switches are more capable

than the spec sheet ratings suggest, but safety factors are necessary to guarantee compliance across a

broad range of applications.

Let’s say that you are looking at a small Form‐C switch with rhodium contacts rated at 3W, 120V DC,

and 0.25A. Can you switch this reed at 120V DC and 0.25A and expect 10 million operations? No. The

effective load on this switch would be 30W…more than 10 times the maximum power rating! The

switch can be operated at max voltage, or max current, but not at the same time.

You are searching for a sensor that will operate at 0.5” and release at 1”. The spec sheet provides the

dimensions, electrical ratings, operation direction, and actuator part number, but you would like to

use a different actuator and you aren’t sure yet about the approach direction. The operational

information is specific to the actuator being used in the manner and orientation listed. An actuator

(magnet) can be purchased with a host of different parameters that affect the operational range of

the switch (size, shape, material, Gauss strength, field direction, etc.).

So what do you do if your application doesn’t exactly “fit” the spec sheet for one of our standard

products? Just give us a call or shoot us an e‐mail and we would be glad to provide specific application

assistance. That

switch

can

probably

handle

the

heavy

load

without

failure

if you

operate

it

at

a

reasonable rate and only need it to last for 100k cycles. If you need it to handle that load and still

reach 10 million cycles, we can provide a larger

switch, customize the Rhodium thickness to provide

a higher power rating, or provide you with a

tungsten contact switch. That sensor may work just

fine with your current actuator approaching from

the side instead of end‐on, but the operate and

release distances will differ from the spec sheet

listings. We

can

tune

a standard

product

or

custom

engineer a new sensor for your specific application.

HSI has the technical expertise to answer your

questions and multiple product lines to meet your application needs. Custom reed switches and

proximity sensors are what we do…better than anyone in the industry.



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Reed Switch CustomizationAuthor: Mark MandrellEach switch and sensor that we manufacture has its own particular characteristics, and how you

handle one

may

not

be

the

same

as

the

other.

Knowing

how

to

correctly

manipulate

a switch

is

very

critical to the proper operation of that device for its intended purpose. Many times we have

customers contact us with questions as to why they are experiencing problems when they are not

getting the results that they are expecting, or when damage to the switch occurs..

A reed switch may just look like a piece of glass with leads protruding from it, but really it is a very

intensely engineered special device that works in an amazing way,

and the methods used to customize it for your particular

application are very critical. The stresses induced at the time of

modification can

damage

or

severely

change

the

performance

from its original design function. A simple bend of a lead without

the correct gripping method can be all it takes for that device to

not work as it is intended, and this can lead to great frustration for

our customers.

With 45 years of leading the way in custom design and

applications for this industry, we here at HSI have engineered solutions to these production,

modification and testing processes. And let me tell you, we face new modification challenges every

day! To put it in the words of my great grandmother, “It’s like being a goose and waking up in a new

world every

day.”

This

has

been

my

experience

with

all

the

customer

applications

I’ve

seen

through

the years. It’s crazy (amazing?) to think about how many places and ways that our customers can

dream up of where and how to use our products; our customers put us to the test in a new way every

day!

When it comes to the tooling required to make necessary modifications to a product‐‐whether they

are requested by a customer for a specific application, or whether it is a requirement for the switch to

work precisely in one of our custom proximity sensors‐‐you can’t just go out and purchase it. We have

a fully equipped precision machine shop in‐house, along with machinist that have a combined

experience of

over

60

years,

and

we

design

and

manufacture

all

of

our

own

equipment

to

be

able

to

meet these special needs. From the machines that produce the switches, to the benders, the cutters,

the fixtures to perform the welding functions, the potting of the proximity sensors and the testing, we

do it all.

Please let us utilize our knowledge and ability to meet the unique needs that your project demands.

Our experience and expertise can save a lot of unnecessary frustration, damaged product, and the

most important project commodity of all that can never be regained, TIME!



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Wisdom from the Design JourneyAuthor: Eddie Shearer

In my

years

of

work

with

product

design

at

HSI

Sensing

I have

been

involved

with

many

projects

that

went very smoothly and also several that did not. Is there a key characteristic that largely determines

on which side of that fence a new project will land? I believe that there is.

In the broadest possible terms the phase at which we enter the project has the biggest impact on the

effectiveness of the solution we can provide. Ideally we want to be part of the design discussion from

the very beginning. We want to help with establishing the electrical circuit and also with the physical

constraints. Choices about component layout and material type greatly affect the outcome for

magnetically‐based switching and/or sensing solutions.

I do understand that many of the projects that reach my desk are retrofit applications. Someone (who

usually does not work at the company anymore) used a different solution originally, and now, for

whatever reason, need us to keep the same geometry but use a reed switch. Most of the time we can

still provide a solution in these difficult situations, but that is an article for another day.

Today I am talking about the design projects that are basically starting from a blank page. The

customer knows what they want the end result to do, but still they don’t call us right away. I can only

surmise that they oversimplify the reed switch. A reed switch is just a piece of glass with some

magnetically sensitive blades right? How hard can that be? They will go shopping online to find the

smallest switch

available

without

checking

the electrical ratings for that switch. They

end up allowing room for a small switch

but need the load capabilities of one five

or ten times the size.

I have seen occasions where customers

allowed space for a switch and a magnet

but didn’t understand the relationship

between the

two,

so

they

designed

the

magnet to deliver magnetism to the switch

in an inefficient way. By the time they are

able to test and realize it doesn’t work as

they planned, other things have been put

into place that prevent moving the magnet

and/or switch to make it work correctly.

There have been times when the designer did a great job picking the correct switch and providing a





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A New Solution to an Old ApplicationAuthor: David Posey

The world is full of mechanisms, machines and devices with moving

parts. Many of these "old" pieces of equipment or technology have

mechanical switches converting mechanical motions into electrical

signals. Often those mechanical switches get dirty, the contacts have

aged, or there are new requirements for environmental safety or

switch longevity or performance. There is always a fear that it will be

very difficult to replicate the exact performance of the old mechanical arrangement with a new

sensing method ‐‐ "difficult" can mean too expensive, too time intensive, or that the expertise doesn't

exist to make a fail‐safe transition.

Time and time again HSI Sensing is consulted to convert a specific mechanical motion into an electrical

signal. Most of the time we are assisting, guiding, or providing the full service for our customers to

convert the mechanical motion into an electrical signal. The pushback that sometimes occurs comes

from the perception that reed switch technology is not as capable as the old mechanical switches. This

often is true; however, we always ask “what signal are you actually switching?” The previously

employed mechanical switches are often rated 3, 5, or 10 amps switching capability. But in the new

application ‐‐ now typically signalling a computerized control system ‐‐ the rating is often below 0.1

amp. Hermetically sealed switches are very capable in these signal applications.

Mechanical switches are also activated by levers that sometimes move very small amounts. With the

correct type of magnet, polarity, switch type (engineered for close differential), and shielding, the

same motion can be achieved with reed switches fabricated into a proximity sensor. Now the sensor is

working in a "non‐contact" method. In other words, mechanical switches need a lever to move or a

button to be pushed, requiring physical contact that is also a method for wear. The reed switch‐based

proximity sensor has no need of physical contact.

Typical mechanical switches can be built with one or two sets of contacts. Reed switch‐based

proximity sensors can have one, two, three, or more sets of contacts in one proximity sensor housing.

If redundancy

is

needed

for

multiple

independent

signals,

this

type

of

assembly

should

be

considered.

Some may say reed switch technology is ancient ‐‐ it was invented in 1930s and 1940s. That is correct.

But the use of reed switches in various applications is far and wide. They are cost efficient in

manufacturing, simple to apply, require no power consumption to operate, and are hermetically

sealed for long life. Difficulty or simplicity is based on the knowledge of the application and how to

apply the technology. HSI Sensing has many years of experience in solving conversion of mechanical

motion to electrical signal. Contact us to see how we can help your conversion.



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Making Sense Author Profiles

David Posey, Chief Technology OfficerDavid didn’t invent the reed switch. But he spent 30 years perfecting it. He's

engineered solutions for pacemakers, jumbo jets, and for products like

submarines and the space station that push the boundaries of where we go

and what we do next. No one else in the world has seen all he’s seen, and

no one else loves putting that experience to work for you more than he

does.

Eddie Shearer, Product Development EngineerA mechanical engineer and 13‐year veteran at HSI Sensing, Eddie

understands that no two customer's challenges are alike, and he views the

task of custom engineering as a creative process.

"We start with a problem," he says. "At the end of the process we're holding

a device that solves that problem. It's the most rewarding thing I do."

Lawrence McClure, Product Design EngineerLawrence thrives on the intensity it takes to solve a customer's problem

without backing down, and he enjoys the process of using his mind and his

hands in tandem to engineer solutions to real‐world design challenges.

"The most rewarding thing to me is finishing a project," he says. "It's seeing

an idea come to life that started with just a sketch."

Zack McGill, Product Quality EngineerLike most engineers, Zack is a creative problem solver, and he loves putting

that skill to work for our customers. He believes when you push a product to

new limits and find new ways, everybody wins.

"You'd be surprised what a reed switch is capable of if given the chance," he

says. "We might even make it dance."



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Mark Mandrell, Senior Designer/Technical AdvisorMark was privileged to begin his 22‐year journey with HSI by learning

directly from its founder, Bill Posey, and experiencing first‐hand many

experiments and ground‐breaking products.

"It would be nice if you could open up a book and find that kind of

knowledge," he says. "I take great pride in being able to pass that

knowledge on in order to meet our customers’ needs."

Documents

Making Sense Volume 1