Door Bell

Thread Starter

Big Dingus

Joined Oct 22, 2018
25
Hi folks.
This isn't a homework question as I left school about 45 years ago, but I didn't want to bother the experts with trivia.

I have a doorbell that is a long way from the sounders, which means when people push the button they can't hear the sounders. This causes all sorts of problems.
What I want to do is fit a buzzer behind the bell push. (Very limited space)
I have taken my 240vac supply through a transformer to supply 18vac, then through a rectifier to give 18vdc. This runs two sounders through a solid state relay.
I purchased a dc buzzer to put behind the bell push but I can get it to buzz. I was hoping just putting it in series would have worked.
Thinking it may be voltage, I've tried dropping the voltage by using two resistors, but still no luck.
The resistors were 6k2 and 2k2. (Was thinking too big).

I used Vin X R1 / R1+R2 = Vout
I've checked the buzzer on a 6v battery and it's fine.

Can anyone help please?

Moderator edit: Moved from Homework Help
 

MrChips

Joined Oct 2, 2009
25,066
6k2 sounds way too high. Try 1kΩ.
Can you provide us with details of the buzzer or a photo of the buzzer showing part number or technical data?
 

Dodgydave

Joined Jun 22, 2012
10,139
What is the resistance of the solid state relay, ??
you could put a 1K resistor across the solid state coil, and then try to put it in series with the bell push.

Post a drawing of what you have..
 

Thread Starter

Big Dingus

Joined Oct 22, 2018
25
Mr Chips I'll try that.
Alec sorry for the diagram. Treid my best.
DD have a look.
Rolo (Hope your not the last one) as requested.

The buzzer is Power supply: 2.5-5.5V @60ma Diameter: 10m Thickness: 2.7mm. (Due to available space)
I used Voltage devider to drop the 18vdc to 5vdc at the bell push.
The relay was one I had sitting around>


Scan200001.jpg
 
Last edited:

BobTPH

Joined Jun 5, 2013
4,322
I purchased a dc buzzer to put behind the bell push but I can get it to buzz
What is the voltage and current rating of the buzzer?

What is the current through the button circuit when closed?

You cannot simply put them in series because that would deprive the doorbell of power and probably overpower the buzzer. You are lucky it was not destroyed in the process.

I don't see any way to make this work without separate power for the buzzer. It is much like putting an indicator in a light switch to tell you when the light is on. It is easy to make it tell when the light is off, but not when it is on. That is because when the light is on, all you have is a wire carrying a current with practically no voltage across it.

Bob
 

Thread Starter

Big Dingus

Joined Oct 22, 2018
25
Thanks Bob.
Buzzer is 6v.
Unfortunately I only have a 2 wire installed or i would have done just that.
I haven't measured the current. I'm sure it's low.
Both the bell and the buzzer are of no value really, so not too worried if my efforts burn them out.
Sounds like I'll need to replace the cable to a 4 wire.
I appreciate your input.
 

BobTPH

Joined Jun 5, 2013
4,322
The trouble is, that if you place anything in series with the button circuit, it has to drop 6V to operate the buzzer. And that is 6V less that the doorbell sees.

Bob
 

Thread Starter

Big Dingus

Joined Oct 22, 2018
25
As you say, but even doing that the bells work. However the buzzer doesn’t. Even in series.
it’s a difficult, if not impossible, but I’m going to look at running a 4 wire.
 

Tonyr1084

Joined Sep 24, 2015
6,636
If you thought putting the buzzer in series with the switch, it should work. But then you're dropping a lot of voltage through either the strikers on the doorbells or through the buzzer. Or both. In theory, an 18 volt solenoid in series with a 6 volt buzzer is going to require 24 volts. If the bells still work then the buzzer is too low a resistance, which means the bells see the buzzer as just a very long wire in a very small space.

The right way to make the buzzer buzz is to add a third wire - a return wire. Connect the buzzer to the switched side of the switch, not the supply side. When you push the button the buzzer will buzz. But at 18 volts - you're going to have to add in some resistance so you don't burn up the buzzer. To figure the correct size resistor you need to know the resistance of the coil of the buzzer. Then you need to make a voltage divider (resistor in series with the buzzer) so that the resistor drops 12 volts. The secret is the resistance of the coil. Know that and you can calculate the required voltage at 6 volts. That will tell you the amps through the buzzer. Then you need to drop the other 12 volts via a resistor. And likely it's going to be a pretty big resistor, wattage wise.
 

MisterBill2

Joined Jan 23, 2018
10,602
Hi folks.
This isn't a homework question as I left school about 45 years ago, but I didn't want to bother the experts with trivia.

I have a doorbell that is a long way from the sounders, which means when people push the button they can't hear the sounders. This causes all sorts of problems.
What I want to do is fit a buzzer behind the bell push. (Very limited space)
I have taken my 240vac supply through a transformer to supply 18vac, then through a rectifier to give 18vdc. This runs two sounders through a solid state relay.
I purchased a dc buzzer to put behind the bell push but I can get it to buzz. I was hoping just putting it in series would have worked.
Thinking it may be voltage, I've tried dropping the voltage by using two resistors, but still no luck.
The resistors were 6k2 and 2k2. (Was thinking too big).

I used Vin X R1 / R1+R2 = Vout
I've checked the buzzer on a 6v battery and it's fine.

Can anyone help please?

Moderator edit: Moved from Homework Help
OK, so the only current through the push button is the current to operate the solid state relay. And that small current will not operate the buzzer that is in series with the solid state relay.
What voltage does the solid state relay require, and are you also powering the solid state relay with that same 18 volts DC?
If you add a resistor across the solid state relay to increase the current through the buzzer that may work. try 100 ohms or so across the control terminals of the solid state relay and if the 2 sounders work but not the buzzer, then try about 50 ohms, or use a 47 ohm resistor if 50 ohms is not easily available.
 

MisterBill2

Joined Jan 23, 2018
10,602
If you thought putting the buzzer in series with the switch, it should work. But then you're dropping a lot of voltage through either the strikers on the doorbells or through the buzzer. Or both. In theory, an 18 volt solenoid in series with a 6 volt buzzer is going to require 24 volts. If the bells still work then the buzzer is too low a resistance, which means the bells see the buzzer as just a very long wire in a very small space.

The right way to make the buzzer buzz is to add a third wire - a return wire. Connect the buzzer to the switched side of the switch, not the supply side. When you push the button the buzzer will buzz. But at 18 volts - you're going to have to add in some resistance so you don't burn up the buzzer. To figure the correct size resistor you need to know the resistance of the coil of the buzzer. Then you need to make a voltage divider (resistor in series with the buzzer) so that the resistor drops 12 volts. The secret is the resistance of the coil. Know that and you can calculate the required voltage at 6 volts. That will tell you the amps through the buzzer. Then you need to drop the other 12 volts via a resistor. And likely it's going to be a pretty big resistor, wattage wise.
Tony forgot that the button is only switching the power to the control terminals of that solid state relay. That changes the game quite a bit.
 

Thread Starter

Big Dingus

Joined Oct 22, 2018
25
Thanks MrB. I'll try that first.
Running a new cable would probably be impossible, but I'm checking that today.
If I could get a 4 wire in I will and that would be job done.

To answer your questions.
I am powering the relay with the same 18vdc.
Now off to see if I can get those resistors 100 and 47 ohms.
 

BobTPH

Joined Jun 5, 2013
4,322
Okay, I missed the fact that the button was powering only an SSR. That means about 10mA, not enough to power the buzzer.

Does the SSR use an external resistor to limit current? If it does, and if you can tell us the current needed by the buzzer, I can give you a circuit that will operate both in series.

Bob
 

Tonyr1084

Joined Sep 24, 2015
6,636
I said: "The right way to make the buzzer buzz is to add a third wire - a return wire. Connect the buzzer to the switched side of the switch, not the supply side. When you push the button the buzzer will buzz. But at 18 volts - you're going to have to add in some resistance so you don't burn up the buzzer. To figure the correct size resistor you need to know the resistance of the coil of the buzzer. Then you need to make a voltage divider (resistor in series with the buzzer) so that the resistor drops 12 volts."

"And likely it's going to be a pretty big resistor, wattage wise."

This shouldn't affect the SSR whatsoever.

Here's what I had in mind when I said adding the third line:

1583246221474.png
 
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