Sealed Subminiature Basic Switches
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To introduce the basic knowledge of snap-action switches and overview Omron’s D2SW switches
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Sealed Subminiature Basic Switches
- 3. Overview of Basic Switches Actuator The actuator is a mechanism incorporating the pushbutton and lever. External force imposed on it is relayed to the internal spring mechanism, thus operating the movable contact to turn the switch ON or OFF. Terminals The terminals are where electrical wires are connected for input and output of the switch. Switch Case Also called the housing. It protects the switch internal mechanism with electrical insulation and mechanical strength. Contacts Securely opens and closes the electrical circuit. Snap Action Mechanism Performs a snap action using a superior conductive spring.
- 6. Contact Form Symbol Name SPDT SPST-NC SPST-NO Split-contact Type Maintained-contact Type DPDT
- 9. D2SW Actuator and Terminal Offers Pin Plunger Hinge Lever Simulated Roller Lever Hinge Roller Lever PCB Terminals Quick Connect Terminals Solder Terminals Wire Leads
Hinweis der Redaktion
- Welcome to the training module on Sealed Subminiature Basic Switches.
- This training module will introduce the basic knowledge of snap-action switches and overview Omron’s D2SW switches.
- A Basic Switch is a small switch with a very small contact gap and snap-action mechanism and with a contact structure that switches for a specified movement and specified force enclosed in a case with an actuator provided on the exterior of the case. The diagram shows the basic switch structure. A basic switch is mainly comprised of five components: actuator, contacts, switch case, snap action mechanism and terminals.
- A snap-action mechanism is the mechanism by which the moving contact quickly moves from one fixed contact to another fixed contact with minimal relation to the speed at which the switch is operated. The faster the contact switching speed, the shorter the connection time for arcing generated between the contacts. To perform this quick action, a spring mechanism is used. The spring mechanism generally uses a dead point, which is the critical action point when one condition changes in a springing manner to another condition. When force is applied to the actuator in the travel direction, pressure builds in the snap spring until the actuator reaches the travel operating position. Then a set of moveable contacts accelerates from its normal position to a set of fixed contacts.
- The contact gap is a distance between the fixed contact and movable contact when they are separated from each other. The smaller the contact gap of a switch mechanism is, the less the movement differential (MD) is and the more sensitivity and longer durability the switch has. However, such a switch cannot ensure excellent switching performance, vibration resistance, or shock resistance. The contact gap is either 0.25, 0.5, 1.0, or 1.8 mm.
- The contact form is a configuration of switch contacts to input or output an external signal. From the table, you will notice the name of the contact form, like SPDT, SPST, DPDT. The “P” stands for Poles which indicates how many sets of switches are connected to a single mechanical trigger. The “D” means "Throws" which describes the number of switch contact ways.
- From the switch data sheet, you may find the listed specifications. We will spend some time explaining them. First is the rating, which are various parameters, such as current or voltage values, within which the normal operation of the basic switch is guaranteed. The Insulation Resistance indicates the resistance between discontinuous terminals, between terminals and non-current-carrying metal parts, and between terminals and ground. Contact Resistance is the electrical resistance of the contact point of contacts. Generally, the contact resistance includes the conductive resistance of the spring or terminal section. Dielectric Strength is the threshold value up to which insulation will not be destroyed when a high voltage is applied for 1 minute to a predetermined measurement location. Shock Resistance shows the range of shock for which the components of the switch will not be damaged and for which operating characteristics are maintained when mechanical shock is applied to a switch during transportation or installation.
- The D2SW snap-action switch family is a sealed subminiature basic switch Conforming to IP67. Use of epoxy resin assures stable sealing, making this switch ideal for places subject to water spray or excessive dust. They are ideal for automobiles, automatic vending machines, refrigerators, ice-making equipment, bath equipment, hot-water supply systems, air conditioners, and industrial equipment, which require high environmental resistance. The switch family is available in models offering choices of four different actuators, three contact arrangements and terminal selections such as solder, quick-connect terminals, PCB terminals, molded lead wires or even-pitched PCB terminals. The variety of available combinations makes them adaptable to a wide range of applications and the needs of many end users.
- This switch family is available in four different actuators, including pin plunger, hinge lever, simulated roller lever, and hinge roller lever. It also offer four selections such as solder, quick-connect terminals, PCB terminals, and molded lead wires or even-pitched PCB terminals.
- The life expectancy of a D2SW switch is presented by electrical life and mechanical life. The electrical life means the duration in which the normal switching operation is performed under the rated load (resistive) as long as the switch is used with the rated over travel (OT). The mechanical life indicates the duration in which the normal switching operation is performed without the contacts energized as long as the switch is used with the OT. The value listed in the datasheet is not guaranteed, it is just a reference value.
- Here is the model numbering system. The D2SW is the series number. The first part indicates electrical rating. The second part shows the actuator types, if it is none, that means the switch is pin plunger. The last one stands for terminal types.
- Thank you for taking the time to view this presentation on “ Sealed Subminiature Basic Switches” . If you would like to learn more or go on to purchase some of these devices, you may either click on the part list link right beside the play button on the TechCast portal, or simply call our sales hotline. For more technical information you may either visit the Omron site, or if you would prefer to speak to someone live, please call our hotline number, or even use our ‘live chat’ online facility. You may visit Element 14 e-community to post your questions.