How to wire the normally open and normally closed contacts of a push button switch

Thread Content

When the button does not function properly, use a multimeter to check it; if there is a connection when the button is pressed, it is a normally closed contact, while if there is no connection when the button is pressed, it is a normally open contact. Push button switches come in normally open and normally closed types, as there are situations where normally open contacts are required and other situations where normally closed contacts are needed. For example, a start button requires a normally open contact, while a stop button requires a normally closed contact. To ensure versatility, push button switches typically have two contacts of each type (one normally open contact and one normally closed contact). The difference between these and the switches on our lighting panels is that, when the button is released, the contacts return to their state when the button was not pressed (although there are also buttons that can maintain their position). The button does not have a maintenance effect. The lighting panel switch is a circuit breaker that provides protection against overload and short circuits. Once closed, it remains in that position as long as there are no problems, unless someone manually opens it. The reason for choosing a normally closed button switch is as follows: 1. In terms of the timing of operation, it takes much less time for a normally closed contact to go from closed to open compared to the time it takes for a normally open contact to go from its natural state to closed. Perhaps you might say, how can there be much less? Such a short period of time doesn’t matter. But I would say this is particularly important when an emergency stop is required due to a seizure risk. At this point, even the shortest amount of time, whether it’s in milliseconds or microseconds, is extremely important. In such a short period of time, using the normally open contacts might not have stopped the machine or disconnected the switch, resulting in severe damage to the machine or injuries to people. But by using normally closed contacts, it is possible to stop the machine or reduce the time during which a person might be exposed to electric shock, thereby preventing all of this from happening. 2. In terms of button design, whether the emergency stop button has normally closed or normally open contacts, it will spring back up once it is not pressed fully, thereby preventing the action from taking effect. When normal-open contacts are used, the emergency stop function has no effect unless the emergency stop button is pressed fully (as the normal-open contacts are not closed); whereas with normal-closed contacts, it’s different – the emergency stop function takes effect as soon as the contacts are activated, regardless of whether the emergency stop button has been pressed fully or not. 3. In terms of its control circuitry, it goes without saying that the most basic function of an emergency stop button is to enable immediate parking in urgent situations, thereby preventing mechanical failures or injuries. However, due to the prolonged operation of the machine, some of the circuits, especially those for emergency stop, may develop faulty breaks. At this point, if the emergency stop button uses normally open contacts, some circuit faults related to the emergency stop will go unnoticed; by the time those faults are detected when using the emergency stop button, it will already be too late. When normally closed contacts are used, if a fault occurs in some of the circuits related to the emergency stop, at most it will result in the machine coming to a stop, with relatively minor losses.