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:
- Straight PCB pins
- Angled PCB pins
- Soldering eyelets
- Quick connect (Faston)
- 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;
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.