Skip to main content

Understanding the power to my door bell

Hi guys,

I would like to understand how my outside door bell light works.

Based on what I understand (the outside wire) it's one wire getting interrupted & when pressing the door bell it creates contact resulting in the inside door chime to move and make ding dung sound.

But how does the actual light outside on the bell light up since it's one wire (I.e. Positive wire)? As well as when I measure the voltage on the wire itself I'm getting 24V.

How is that possible I would like to understand that.

Same thing with my thermostat wire, when I measure the voltage I'm getting 24 volts but based on my understanding it's one wire making contact when requesting for heat. (It's heat only zone) so how come I'm getting 24 volts

Answered! View the answer I have this problem too

Is this a good question?

Score 1

Comments:

@abrahamyaris that should be an AC circuit so no positive wire. What voltage do you get when you measure AC? That is a really interesting question :-)

by

I'm getting 24vac when I'm putting my multimeter on each of the door bell wires.

by

I have 31 volts AC AT my doorbell button. Is this an anomaly??

by

Frase the wire that it gets power from. You’ll find it connected to a 24v transformer being fed by 120v.

by

Trace the wire, you can frase it too but I can’t help you there!

by

Show 7 more comments

Add a comment

6 Answers

Chosen Solution

Your door bell is being fed from a step down transformer. Somewhere in your house is a small transformer that is getting 120VAC (primary) and stepping it down (secondary) to a lower AC voltage between (typically) 16 to 24VAC. I have seen the transformers mounted near the breaker panel and sometimes in ceilings and walls. 120 is never wired to the momentary switch (door bell push button), it's a shock hazard.

120VAC > transformer > switch > bell or chime.

When they say one wire interrupted, it's because the switch is in line on the same wire or in series, breaking and making a connection on the send or return wire, it doesn't matter which, you are making and breaking one side of a loop. Not across the send and return, that would create a short when you push the switch.

you are metering voltage at the wires because you have an open circuit. If the switch is wired and you push it closed you will read no voltage because both leads of the meter will be at the same level. If you move one lead to ground then you will read a voltage.

Was this answer helpful?

Score 3
Add a comment
Most Helpful Answer

@abrahamyaris , Abraham, are you sure your door bell button only has one wire, I have not seen this before. Check link below as this is what I have always seen for low voltage door bells with a transformer. Normally a lighted button will always be on because the bulb circuit is complete until you press the button. When you press the button it breaks contact with the button/bulb(button light goes out) and this is where the bell contacts come into play, while button pushed the bell rings because the second contacts in button assembly are being used, but there is no light on the button because the internal contact to the button light is broken.

I hope this explains it OK, Good luck.

I hope this helped you out, if so let me know by pressing the helpful button.

http://diyhousehelp.com/how-to/doorbell-...

Was this answer helpful?

Score 5

Comments:

How is the light on the bell lightened up?

Doesn't a bulb need to have positive & Negative In order to light up?

The wire that comes from the transformer to the button only provides one I.E. Positive (& than it travelers to the chime when the button is pressed)

by

@lpfaff1 @abrahamyaris do not forget that this is an AC circuit, same with your thermostat. Let's not focus on the light but on the fact that you measure 24V on the wires of the doorbell switch. I have a couple AC transformers and will see if I can prove it tomorrow so stand by ;-)

by

Add a comment

Here is how the light stays on when the switch is in the open position ....

http://sloanbooks.com/wiring/utilitech-d... <— dead link!!!!

Look down about 3/4 of the way down the page to see the diagram of a typical lighted doorbell switch.

stupid "dead-the-next-week" hyperlinks - HERE:

Block Image

Was this answer helpful?

Score 5

Comments:

That LED will go out when the switch is closed however, as the switch has created a short and all current flows through the switch.

by

Yes they do, of course it has already served its purpose at that point.

by

hyperlink is still going almost 4 years later! this helped me, btw

by

Add a comment

In commercial and residential intrusion and fire alarm systems circuits are typically DC.

However, most residential doorbells are 24vac. An ac transformer is simpler and cheaper to make. As you can see the light and the doorbell switch are in parallel with each other. When the switch is idle, current runs through the light, illuminating it, resistance is high through this circuit limiting the current that would pass through the bell, not enough to make it ring. When the button is pushed, the circuit is completed with no resistance through the switch, allowing the bell to draw the current it needs to ring.

Was this answer helpful?

Score 3

Comments:

from an electronics degreed person, very well said. What adds to the confusion is that I didn't realize that light was LED, though it was incandescent.

by

@Joe Fierova Before the advent of led illumination these were small neon bulbs I believe.

by

Add a comment

Hi @g001

You may have to add a resistor in series with the lamp as shown in the image in the Most Helpful Answer above.

For some reason your door bell doesn't like having the lamp in circuit all the time as it may be drawing too much current therefore the continuous ringing.

Placing a resistor as shown will however dim the light from what it is now, so you may have to experiment as to its value i.e. high enough to work correctly but still low enough so that the lamp provides sufficient illumination

Also what is the make and model number of the door bell as you supplied the make and model number of the door bell push button?

Was this answer helpful?

Score 1

Comments:

Hi mate, thanks for your reply not quite sure which diagram you are referring to.

The model is Byron 00.640.20 7730 Wired surface mounted bell push button 7730

by

@g001

Apologies, I meant the image in the Most Helpful Answer above which shows the typical wiring of an illuminated push button but not in your case as there is no limiting resistor.

Also bit confused as a Byron 00.640.20 7730 Wired surface mounted bell push button 7730 is only the push button and not the door bell (or chime) to which it is connected. Was hoping perhaps to find the manual or schematic for the actual door bell to see if there were any options for connecting an illuminated push button. Some have dip switch or jumper plugs that can be altered to accommodate various scenarios.

The resistor is used to lower the current passing through the push button so that it doesn't trigger the door bell but allows the lamp to be lit.

When the button is pushed the "lamp circuit" i.e. lamp + resistor, is by-passed by the push button switch contacts which allows more current to flow and the door bell reacts accordingly

by

Sent diagram via email

by

From the byron website regarding continuous ringing:

Constant ringing or buzzing sound

If your wired door chime does not stop ringing or you can hear a loud buzzing sound when connected then please check the below:

[br]

For Electronic door chimes that play an electronic melody:

* Check that you are not using a lighted bell push. Remove the light from the bell push or change the bell push to a non-lighted version.

* Check there is not a short circuit and the wire connections inside the chime unit or inside the bell push are not touching each other.

* Check the wired bell push is not sticking when pressed, if it is then take it apart and clean using a dry cloth. Sometimes using a light spray oil to lubricate the button can help with this.

[br]

For Traditional door chimes that ring a bell or Ding Dong:

* Check there is not a short circuit and the wire connections inside the chime unit or inside the bell push are not touching each other.

* Check the wired bell push is not sticking when pressed, if it is then take it apart and clean using a dry cloth. Sometimes using a light spray oil to lubricate the button can help with this.

by

Show 3 more comments

Add a comment

Guys,

You should be getting a DC voltage not AC. This powers interior wired fire alarms and bells. Most circuits that have interrupt switches/ buttons / remotes use DC power. Think everything with a battery and button combination. All LEDs use DC power.

Was this answer helpful?

Score 0

Comments:

David, I'm sorry you need to study electronics a bit. There are so many incorrect assumptions here I don't know where to start.

by

Low Voltage systems are DC, but old school door bells are low voltage AC.

by

An LED is a diode. You could run an LED from low voltage AC as long as the proper current limitation is there (a resistor). The diode would be on during the positive portion of the waveform and off on the negative swing. In other words it will be on in the forward bias (conducting) when it sees the positive swing of the AC.

by

ReallyColdUpHere is absolutely correct. This is a fundamental misunderstanding of electronics. Switches and buttons can be used on AC power -- look at the wall switch running your lights in your house. AC, right? And LEDs can use DC power, but can run on AC as well: https://www.manufacturer.lighting/info/6....

by

Add a comment

Add your answer

Abraham Yaris will be eternally grateful.
View Statistics:

Past 24 Hours: 8

Past 7 Days: 110

Past 30 Days: 619

All Time: 61,942