push button vs switch
- Thread starter alitronic
- Start date
Both are switches as mentioned. You choose a switch based on application at design time. In some designs a N/O or N/C push button is the better choice. The designed has an endless array of switches to choose from. You make the choice based on application. I want to start a 40 HP motor drive. I use a N/O push button configured in a latching circuit. I use a large red E Stop N/C push button to open my latched contactor and stop the motor. I want to turn On / Off a simple lamp so I use a simple toggle switch.
Ron
Last edited:
Yes, I mean momentary Contact vs two position.
There are many different styles of switches.
Let us begin with the basic ON/OFF switch or two position switch.
There are rocker switches, slide switches, toggle switches, and rotary switches.
Rocker Switch
Slide Switch
Toggle Switch
Switches are used not only for ON/OFF functions but also for selecting different functions.
Switches are available with different types of actions such as, momentary, 2-way, centre position, locking.
Switches also might have multiple contacts and are labelled accordingly, for example,
SPST = Single pole, single throw
SPDT = Sinple pole, double throw
DPDT = Double pole, double throw
Rotary Switch
Push Button
A push button might have a simple momentary action.
Push buttons are also available in many different styles and actions.
For example, you can select, click on - click off, latching, etc.
You can have keyed or keyless, latching emergency stop (or estop), push button.
A simple push button can be used with intelligent programming for selecting many different functions, for example,
press once - function #1
press twice - function #2
press and hold - function #3
In summary, there are thousands of different styles and actions to choose from and the one you choose will depend on the specific function and application.
Let us begin with the basic ON/OFF switch or two position switch.
There are rocker switches, slide switches, toggle switches, and rotary switches.
Rocker Switch
Slide Switch
Toggle Switch
Switches are used not only for ON/OFF functions but also for selecting different functions.
Switches are available with different types of actions such as, momentary, 2-way, centre position, locking.
Switches also might have multiple contacts and are labelled accordingly, for example,
SPST = Single pole, single throw
SPDT = Sinple pole, double throw
DPDT = Double pole, double throw
Rotary Switch
Push Button
A push button might have a simple momentary action.
Push buttons are also available in many different styles and actions.
For example, you can select, click on - click off, latching, etc.
You can have keyed or keyless, latching emergency stop (or estop), push button.
A simple push button can be used with intelligent programming for selecting many different functions, for example,
press once - function #1
press twice - function #2
press and hold - function #3
In summary, there are thousands of different styles and actions to choose from and the one you choose will depend on the specific function and application.
Attachments
First, don’t confuse the actuator type with the switch. There are both fixed and momentary contact switches in every actuator type. Whether it is a toggle, rocker, slide, rotary, or pushbutton the choice of actuator is distinct from the choice of momentary versus fixed operation.
Some types of actuators may be more suited to different configurations—for example a selector with a large number of poles and throws is probably going to call for a rotary switch for practical reasons, while a low profile switch intended to avoid accidental operation might call for a pushbutton (or some guard but that requires clearance and space).
So far as choosing a momentary switch for something that will latch on and off, as opposed to operating only when pressed, you will find that in most cases whatever is being switched is also controlled by something else (e.g.: a microcontroller or secondary switch) and so having a fixed position switch is not a sensible option.
Instead, the momentary pushbutton is connected to whatever otherwise controls the device—a µC, a latching contactor or relay, &c—so that more than one signal can operate it. While you could use a fixed switch with a µC by programming it to respond to a state change rather than the absolute position of the switch, this means that the position of the switch no longer corresponds to the state of the circuit power which is a bad user interface.
This is sometimes done as a compromise when converting an existing switch to multipoint operation. A common example of this is for home automation conversion of lighting that uses a wall switch. Since it is desired that the light be controllable from the original switch and at the same time under computer control, the existing toggle switch becomes just an input to the computer part of the system and its state is only used to indicate a desire for the state of the light to change from what it is.
So, if the light is off, turn on, and the reverse, leaving the position of the physical switch in some random state not corresponding to the state of the light’s power. If this was a design from first principles it would be a case where a momentary pushbutton might be more suitable possibly along with an indicator to show the circuits state if the light itself was not collocated with light (say, an outdoor light).
So, how do you choose? Take into account the space, mechanical, and human factors requirements to choose an actuator type; also consider the circuit under control of the switch as described above. While you could write out a list of rules for this, designers have an intuitive grasp of most of the factors involved and when building the first prototype will have a strong idea of what it suitable.
After testing, it may become clear that something relevant wasn’t considered initially. This will probably be related to the mechanical aspects of the switch affecting ease of operation, unintended operation, or durability—but the process of prototyping can provide surprises as the idea becomes a physical thing that has to fit into the world.
That’s why iterations of prototypes are so important, right from the beginning, for subsystems and the entire device being developed. Sometimes people try to avoid multiple prototypes as a cost saving measure, or skip prototyping altogether, but this only means that version 1.0 is a prototype and is going to have problems. The customer is then the beta tester and the early adopters—the most important customers—will have a bad experience. This is both very poor practice and unfortunately very common, particularly with software.
(Insert extensive rant concerning this here, but I am going to stop while I am still mostly on topic.)
I hope that helps answer your question. If you have any more, please ask.
Some types of actuators may be more suited to different configurations—for example a selector with a large number of poles and throws is probably going to call for a rotary switch for practical reasons, while a low profile switch intended to avoid accidental operation might call for a pushbutton (or some guard but that requires clearance and space).
So far as choosing a momentary switch for something that will latch on and off, as opposed to operating only when pressed, you will find that in most cases whatever is being switched is also controlled by something else (e.g.: a microcontroller or secondary switch) and so having a fixed position switch is not a sensible option.
Instead, the momentary pushbutton is connected to whatever otherwise controls the device—a µC, a latching contactor or relay, &c—so that more than one signal can operate it. While you could use a fixed switch with a µC by programming it to respond to a state change rather than the absolute position of the switch, this means that the position of the switch no longer corresponds to the state of the circuit power which is a bad user interface.
This is sometimes done as a compromise when converting an existing switch to multipoint operation. A common example of this is for home automation conversion of lighting that uses a wall switch. Since it is desired that the light be controllable from the original switch and at the same time under computer control, the existing toggle switch becomes just an input to the computer part of the system and its state is only used to indicate a desire for the state of the light to change from what it is.
So, if the light is off, turn on, and the reverse, leaving the position of the physical switch in some random state not corresponding to the state of the light’s power. If this was a design from first principles it would be a case where a momentary pushbutton might be more suitable possibly along with an indicator to show the circuits state if the light itself was not collocated with light (say, an outdoor light).
So, how do you choose? Take into account the space, mechanical, and human factors requirements to choose an actuator type; also consider the circuit under control of the switch as described above. While you could write out a list of rules for this, designers have an intuitive grasp of most of the factors involved and when building the first prototype will have a strong idea of what it suitable.
After testing, it may become clear that something relevant wasn’t considered initially. This will probably be related to the mechanical aspects of the switch affecting ease of operation, unintended operation, or durability—but the process of prototyping can provide surprises as the idea becomes a physical thing that has to fit into the world.
That’s why iterations of prototypes are so important, right from the beginning, for subsystems and the entire device being developed. Sometimes people try to avoid multiple prototypes as a cost saving measure, or skip prototyping altogether, but this only means that version 1.0 is a prototype and is going to have problems. The customer is then the beta tester and the early adopters—the most important customers—will have a bad experience. This is both very poor practice and unfortunately very common, particularly with software.
(Insert extensive rant concerning this here, but I am going to stop while I am still mostly on topic.)
I hope that helps answer your question. If you have any more, please ask.
MaxHeadRoom
- Joined Jul 18, 2013
- 27,660
As Ron and others have indicated , the regulations in most jurisdictions stipulate an emergency stop for Industrial Electrical applications.
This is traditionally done with a N.C. logic string of devices, P.B's, Limit SW etc, that are opened in the event of a E_Stop which results in the removal all motive power from the machine devices.
This is traditionally done with a N.C. logic string of devices, P.B's, Limit SW etc, that are opened in the event of a E_Stop which results in the removal all motive power from the machine devices.
MaxHeadRoom
- Joined Jul 18, 2013
- 27,660
Lock OFF.!
Prevent some re-start when maintenance being performed..
Or jig changing etc.
That would be it. I actually have one of those around here somewhere.
The infamous somewhere.Ron
MaxHeadRoom
- Joined Jul 18, 2013
- 27,660
One other 'sneaky' type used is palm buttons, these are buttons where an operator has to place each of his hands over each button in order for the machine to start/continue the process.
Some have tried to defeat it by covering one button with some object, It doesn't work, it requires to see the operator body contact. !
i.e. Both hands operating
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