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Why is Micro Switch called a micro switch
Probably because the first producer was the American company called
Micro Switch. And as these products were
very popular, the name micro switch became a generic trademark for all producers.
The company Micro Switch was acquired by Honeywell in 1950. And Honeywell
registered the trademark Micro Switch. Other manufacturers
used the name Snap-Action Switch or Basic Switch.
But the question still remains why the founder of the company, Mr. Schulte,
decided to name his company Micro Switch?
Because they switched micro-amps? Probably not since in 1937 the micro-amps did
not even exist. Because of their miniature dimensions?
Probably yes, at that time they could be considered tiny.
And what exactly is that micro switch?
It is an electric switch (patented in 1932) that is actuated by very little
physical force. Switching happens at specific positions of the actuator (not like other
switches). Relatively small movement at the actuator button produces a relatively large
movement at the electrical contacts, which occurs at high speed (regardless of the speed
of actuation). Typical durability is from 1 to 10 millions of cycles. This durability is
a natural consequence of the design.
Micro switches are not operated by person; it is always some moving part of the
equipment. Common applications are detection (e.g. jammed paper in photocopier, the
presence of material or product). Other application can be a limit switch (for control
of machine tools) or door switch (e.g. fridge).
And which one do we love the most?
We like the Marquardt micro switches. the most. Why? Because it is that
Marquardt that produces electronic keys for Mercedes, Volkswagen and other premium cars
and that Marquardt that produces switches for blue Bosch electric tools. That’s why.
Marquardt has a nice range of micro switches. Three basic sizes - miniature
(Series 1005 and 1080, width about 28mm), subminiature (Series 1050, width about 20mm)
and ultra subminiature (Series 1055, width 13mm).
Then we choose the right terminals and the right type of actuator:
Terminals:
- Straight PCB pins
- Angled PCB pins
- Soldering eyelets
- Quick connect (Faston)
- Cables
Actuator:
- Pin plunger
- Straight lever
- Roller lever
- Simulated roller
- Spring lever
What is important when using micro switches?
First of all, load size and type. Some types of load have much higher inrush
current. E.g. relay has 5 times higher inrush current than nominal, motor 10 times,
incandescent lamp 15 times and solenoid even 20 times. On the other hand, for switching
small loads, do not use a micro switch for high currents. We recommend using micro
switch with gold plated contacts.
For harsh environment (dust and moisture), please use micro switches with higher
IP rating (up to IP67).
We recommend applying a contact protective circuit to extend contact durability,
prevent noise, and suppress the generation of carbide or nitric acid due to arc. The use
of a contact protective circuit may delay the response time of the load. Examples of
such circuits:
-RC Circuit - in systems with power supply of 24-48V, it is effective to connect
the RC circuit in parallel to the load. When the power supply voltage is 100-200V, then
in parallel to the contacts (in this case when AC is switched, the load impedance must
be lower than the R and C impedance)
-Varistor - the use is very similar to RC circuit, even with those conditions
when in parallel to load or contacts. Varistor ensures that no high-voltage is imposed
on the contacts.
-Diode - energy stored in the coil is changed into current by the diode
connected in parallel to the load. Then the current flowing to the coil is consumed and
Joule heat is generated by the resistance of the inductive load. The diode must
withstand a peak inverse voltage 10 times higher than the circuit voltage and a forward
current as high as or higher than the load current.
-Diode and Zener diode - this method will be effective if the reset time delay
caused by the diode method is too long. Zener voltage for a Zener diode must be about
1.2 times higher than the power source.
Ensure that the operating body will work smoothly. The shape of it should be
round or oblique - to prevent shocks to the actuator. And of course, operate the
actuator of a hinge roller lever or simulated hinge lever type from the right (correct)
direction.
Ensure that the stroke to the actuator is set not to exceed the total travel
position. If not, the operating body may damage the actuator or the switch itself, and
the stress applied to the moving spring inside the switch will increase and then, the
durability of the switch may be deteriorated.
And some more details - not to tighten the screws too much - not to deform the
body of a switch. Or when soldering, adjust the amount of solder so that the flux does
not enter the switch, it can cause contact failure.
What are Limit Switches?
Limit switches are used to automatically detect or sense the presence of an object
or to monitor and indicate whether the movement limits of that object have been
exceeded. The original use for limit switches, as implied by their name, was to define
the limit or endpoint over which an object could travel before being stopped. It was at
this point that the switch was engaged to control the limit of travel.
How does a limit switch work?
A standard limit switch used in industrial applications is an electromechanical
device that consists of a mechanical actuator linked to a series of electrical contacts.
When an object (sometimes called the target) comes in physical contact with the
actuator, the actuator plunger’s movement results in the electrical contacts within the
switch to either close (for a normally open circuit) or open (for a normally closed
circuit) their electrical connection. Limit
switches use the mechanical movement of the actuator plunger to control or change
the electrical switch's state. Similar devices, such as inductive or capacitive
proximity sensors, or photoelectric sensors, can accomplish the same result without
requiring contact with the object. Hence, limit switches are contact sensors in contrast
to these other types of proximity sensing devices. Most limit switches are mechanical in
their operation and contain heavy-duty contacts capable of switching higher currents
than those of alternative proximity sensors.
Components of a limit switch
Limit switches consist of an actuator with operating head, the switch body
mechanism, and a series of electrical terminals that are used to connect the switch to
the electrical circuit that it is controlling. The operating head is the part of the
limit switch that comes in contact with the target. The actuator contains is connected
to the operating head, whose linear, perpendicular, or rotary motion is then translated
by the actuator to close or open the switch. The switch body contains the switch contact
mechanism whose state is controlled by the actuator. The electrical terminals are
connected to the switch contacts and enable wires to be joined to the switch through
terminal screws.
Industrial machinery that undergoes automatic operations usually requires control
switches that activate according to the movements involved in a machine’s performance.
For repeat usage, the accuracy of the electrical switches needs to be reliable and their
response rate should be prompt. Due to the mechanical specifications and performance
parameters of different machines, factors such as size, operational force, mounting
method, and stroke rate are important characteristics in the installation and
maintenance of limit switches. In addition, a limit switch’s electrical rating should
be matched to the mechanical system loads that it will be controlling in order to avoid
instrument failure.
Many of our footswitches are suitable for industrial use, we have been supplying to
this sector for many years.
With over 70 years’ experience in developing, manufacturing and
distributing industrial foot switches we have the experience and knowledge to produce
footswitches which offer all the characteristics suited for industrial use.
Characteristics of our Industrial Footswitches
Our wide range of industrial foot
switch models incorporates some of the desired features for products in this
sector including;
Long life
Mechanical Stability
Ergonomic designs
As well as stock products for fast delivery, many of our industrial
footswitches also have the folliowing features:
Customisable features – these include: customised cables, connectors,
electronics, labels, colours, logos and bases.
Single or multi pedal – many of our switches have a multi pedal version
Optional guards – these offer additional user and switch protection
and are spacious for use with safety shoes.
Two Types of Timer Switches
Manual Setting Timer Switch: This type is more common in my country (Malaysia). You
can find two types, either analog or digital. This type of timer switch gives you the
option to set “on-off” periods as many times as you want within the 24-hour period.
You can use this type of timer switch to control not only lights but also other gadgets
like water heaters and air-conditioners. I have two such timer switches installed in my
home. One controls the light at the covered car porch (open-air garage with a roof). The
other controls the sitting area (lounge) of my home. If you look at the photo of my
timer switch, it is set “on” at 18.5
(6:30 p.m.) and “off” at 24 (12 midnight).
Factory-Preset Timer Switch: The other version is set such that when you switch it
on, you can choose the time period for the “off” command. This timer switch can offer
up to as many as six choices for the “on” duration. You can choose from 1 minute, 5,
10, 20, 30 and 60 minutes for the gadget to automatically switch off. I would say this
is useful for those who are forgetful, or families with children, who more often than
not, forget to switch off each time they leave the room. But then again, they may even
forget or too lazy to push the “duration” button after switching on! Worse still, they
may even press the wrong duration” button, either ending in total darkness or wasting
electricity! So far, I have not seen this second version in my country.
- Created: 21-02-22
- Last Login: 21-02-22