# metal push-button switch-with light

Joined Feb 4, 2022
145
I found a link while searching the internet for push buttons I'm trying to understand how this button works

https://forum.mustang.org.au/index.php?topic=35803.0

I found it called metal push-button switch-with light. I am confused in the link, it has given NO, NC and Common which I don't understand.

I want to understand how the LED light turns on when the button is pressed and how to do the wiring of the No, NC and common with AC supply

#### sghioto

Joined Dec 31, 2017
5,082
I want to understand how the LED light turns on when the button is pressed and how to do the wiring of the No, NC and common with AC supply
The switch is designed for low voltage DC, however can work with AC if you don't exceed the specs of the switch. What AC voltage and current will this switch be using?

#### crutschow

Joined Mar 14, 2008
33,325
Show us exactly what you are tying to control with this switch.

Joined Feb 4, 2022
145
I want to understand that how the metal push-button switch-with light designed for AC supply is being connected to AC supply.

Description
220 AC LED ALSO AND 4.5 amp loading capacity. 5 pin = 1 -LED +,1 – LED -, 1 – COM, 1 – NO, 1 – NC.

E N L (AC Supply)

I want to understand how the LED light turns on when the button is pressed and wiring of the No, NC and common with AC supply

#### SamR

Joined Mar 19, 2019
4,911
The Amazon YAMING 220V AC 4.5 AMP STAINLESS STILL ON/OFF TYPE LATCHING PUSH BUTTON 16MM RED POWER SYMBOL switch is NOT illuminated. You are looking at two different switches. One is an illuminated DC switch and the other is a nonilluminated AC switch.

#### ThePanMan

Joined Mar 13, 2020
702
According to the wiring diagram you connect your load to the NO (Normally Open) portion of the switch. When you push the button the contact moves from the NC (Normally Closed) to the NO (which is now closed by the action of the switch). NO and NC are the resting position of the switch. When you push the button the NO becomes Closed and the NC becomes Open. The Common is the connection that is made between the NO and NC contacts, depending on the position of the switch.

The light (LED) is likely internally regulated to operate on 12 volts, but I'm making an assumption. And an assumption like that can lead to damage of the LED if you get the voltage wrong. The red wire provides positive 12 volts (again, assumed) to the LED Anode and the black wire provides a return path (ground) connected to the Cathode of the LED. If you want the light on when you push the button - again, I'm assuming 12 VDC, you connect + 12 V to the common (Blue wire) and the Green wire gets connected to the Red wire and whatever the load is you're controlling. Again, and I can't say this enough - I'm making a gross assumption about the voltage. When you push the button the NO becomes closed and power flows from the common to the NO and to the LED.

This is but one way to hook up the LED. You can also wire it up as a follower - meaning instead of providing power to the LED it provides ground to the LED. In that case the Black wire would be connected to the NO, and the common would be connected to ground. Same but exact opposite. That's all if you want the LED to light when you push the button. You might want the LED lit when the button is NOT pushed. OR you might want the LED lit whenever the car is running and electrical power is present. In that case then the red wire gets connected to a switched + 12 V source and the black wire gets connected to chassis ground. Then when you start the car the switch is illuminated. OR OR OR - - - you can connect the red wire to the dash lights so that the LED is only lit when the lights are on.

As for what you intend to switch - that I can't begin to guess. Or even make a safe bet. So before you hook up anything be clear exactly what it is you're attempting to accomplish. The great guys here will help you succeed in your endeavor. They may also take the time to warn you of unsafe practices. Don't take offense at this - none of us want to be responsible for blowing up your project or injuring you - or worse.

Be safe.

#### ThePanMan

Joined Mar 13, 2020
702
One is an illuminated DC switch and the other is a nonilluminated AC switch.
I missed that fact. Yes, you can't illuminate the LED without more circuitry. And you can't just throw a resistor on it - you can still blow out the LED.

#### crutschow

Joined Mar 14, 2008
33,325

Joined Feb 4, 2022
145
I have seen some equipment which has this type of switch, when we press the button, the light turns on. Just like a panel has a power button, the supply starts only when the power button is turned on.

I was curious to know these things, so I searched the internet, in which I found there switch has no, nc and common pin.

Till now I had seen that NC, NO and Common use only in relays but this is the case in this switch too, so I got confused.

#### crutschow

Joined Mar 14, 2008
33,325
I had seen that NC, NO and Common use only in relays but this is the case in this switch too, so I got confused.
Those are the designations for the switch contacts and they are the same as used with relays.

So you don't have a specific use in mind?

The LED would be connected to circuit common and the contact that has power applied when you want the LED to light.
It depends upon what the switch is controlling.
But for AC you will need additional circuitry, such as a resistor and diode for proper operation of the LED, as noted by others.

Joined Feb 4, 2022
145
So you don't have a specific use in mind?
I don't have the specific in mind yet, but let's say I want to connect metal push-button switch between the AC supply and the SMPS 12V 2A. SMPS should be supplies power only when I first press the button and stop when again I press button

how would be my wiring connections ?

#### crutschow

Joined Mar 14, 2008
33,325
how would be my wiring connections ?
Two types of pushbuttons have been posted on this thread, one with a LED indicator, and one without.
Which are you referring to?

#### ThePanMan

Joined Mar 13, 2020
702
Treat the LED as an independent lamp whose location happens to be inside the switch. Question: How would you wire it up if the LED were two inches away from the switch?

In the example you gave - the switch in the off position has 120VAC connected to either the C or the NO. If you've used the C for the primary connection to the power source and with the switch OFF the power supply (SMPS) is off. When you push the button you switch the 120VAC from the NC to the NO and the NO becomes live, turning on the SMPS. The PS then puts out the correct voltage for the LED and the LED is wired to the output of the SMPS. The LED can't handle 120VAC on its own. It will certainly blow in an instant. And you may have never even seen a glimmer of light from it. The LED will have to be powered from the SMPS. PROVIDED THAT - - - the switch with the LED inside it is rated for the correct voltage and the same voltage as your PS is putting out.

#### SamR

Joined Mar 19, 2019
4,911
It is a built-in function of the DC switch, a design feature if you will, whose circuitry is independent of the NO NC circuit for switch control.

#### MisterBill2

Joined Jan 23, 2018
16,489
I found a link while searching the internet for push buttons I'm trying to understand how this button works

https://forum.mustang.org.au/index.php?topic=35803.0

I found it called metal push-button switch-with light. I am confused in the link, it has given NO, NC and Common which I don't understand.

I want to understand how the LED light turns on when the button is pressed and how to do the wiring of the No, NC and common with AC supply
The LED is independent of the switch, and the LED must have DC power of the polarity marked. Given that no supply voltage is specified for the LED, probably it requires an external current limiting resistor, whose value will depend on the voltage available for lighting the LED.
It appears that a lot of conversation happened since post #1. So this remark is a bit late.

Joined Feb 4, 2022
145
Two types of pushbuttons have been posted on this thread, one with a LED indicator, and one without.
Which are you referring to?
I'm talking about Push button with LED indicator

#### crutschow

Joined Mar 14, 2008
33,325
I'm talking about Push button with LED indicator
That appears to be a momentary action switch so would not be suitable to control a power supply as you stated, without some sort of added latch relay.
Otherwise you need an alternate action pushbutton.

#### Tonyr1084

Joined Sep 24, 2015
7,543
This is what people are telling you. The LED is separate from the functioning of the switch. IF the switch was sold for use on automotive applications then it's likely there's a resistor already connected to the LED. If so - then use on lower DC voltages will produce less light. Use on higher DC voltages will require an extra resistor outside the switch. Depending on that voltage and the already internal resistor - you'll have to calculate the correct resistor to prevent damage to the LED. Failure to add an additional resistor (again on the premises that the switch is intended for automotive applications) may result in damage to the LED.

#### Tonyr1084

Joined Sep 24, 2015
7,543
The LED is independent of the switch, and the LED must have DC power of the polarity marked. Given that no supply voltage is specified for the LED, probably it requires an external current limiting resistor, whose value will depend on the voltage available for lighting the LED.
This much is true. We have no idea what voltage the LED is expected to function at. There may or may not be an internal resistor. If there is no internal resistor then use of an external resistor is mandated. You can not just apply power to the LED and expect it to work properly. Since, as Bill points out, no supply voltage is specified then one must do some testing before applying any voltage of any kind to the LED. Then, from there, you proceed.

But to be sure, again, someone has already said this, if you apply 120VAC - even through the appropriate resistor - you will blow it out.

The LED can't handle 120VAC on its own. It will certainly blow in an instant.

#### Tonyr1084

Joined Sep 24, 2015
7,543
As I suspected - this is automotive applications. Note the two bottom most lines.

Still don't know if this a latching switch. From the texts on the attached it sounds like it's a latching switch. But without a definite statement or switch in hand I can't tell.