How This Door Bell Circuit Work?

[AskerOfGeeks]

https://i48.tinypic.com/fpcmec.jpg
the power of 220v ac is given at J1 and J2.
this is a door bell circuit diagram tat i drew by looking at a broken door bell. i think the bell is working, but the volume is low. so i replaced it wit another speaker of 8 ohm. but still the volume is low. by knowing the working of this circuit i can repair it pls help
also pls show me how to redraw or reorganize the components in the circuit diagram into groups like rectification part, sound producing part etc

 

[dr pepper]

That looks like a simple blocking oscillator, I'd say the whole circuit is the sound producing part, except for d1 and c3 which are the rectifier and smoothing cap.

If the volume is low try replacing c3 and c4, and if that doesnt do it check the resistance of r1, then replace the transistor, if all that fails maybe the trans is faulty.

A larger 8ohm speaker would be more effecient I spose.

All this said I suggest you replace the whole thing for a low voltage bell, 240v on the bell push isnt safe, I was zapped as a kid with something like this.

 

[AskerOfGeeks]

Thanks For Replying Dr Pepper

That looks like a simple blocking oscillator, I'd say the whole circuit is the sound producing part

is there better way to draw this circuit ??

except for d1 and c3 which are the rectifier and smoothing cap

my knowledge says as the circuit is working in low current the voltage should be stepped down before it enters the circuit and i am not able to understand how they accomplished it without a transformer at the input of 220v ac also the 2p3s transformer shown here didnt had anything written over it saying it is a transformer or an inductor ( as it is so small, as much as an inductor ) and how much is the ratio. i concluded it as a transformer because my knowledge says that inductor will hav only two pins.

1.

If the volume is low try replacing c3 and c4

2.

do it check the resistance of r1

3.

then replace the transistor

4.

if all that fails maybe the trans is faulty

i will go through all these procedures but is this the steps tat an expert will follow to repair an electronics, i mean by replacing each component i am asking because to test whether the capacitor or resistor is working or to replace it, i must unsolder them right or is there any other way ??

A larger 8ohm speaker would be more efficient I spose.

mm ok thanku

All this said I suggest you replace the whole thing for a low voltage bell, 240v on the bell push isnt safe, I was zapped as a kid with something like this.

no need to worry, we are using the same voltage rated "bell switches" (with spring) as the standard switches (used for our normal ac lights) are rated

 

[dr pepper]

Different repair guys have different techniques so not sure if that is 'accepted' and I made the procedure so that someone with less knowledge can do it, us engineers also have a bit of a 'nose' for certain faults, I can test certain comps in circuit with special gizmo's (mostly home built), but I'd probably change out the capacitors on this straight away.
As for the volatge, you'll lose some acrross r1 but not much so the whole circuit will run at mains volatge except the speaker (look at the voltage rating of the mentioned caps, I bet they are 450v), the reduction to the speaker will be done by the aforementioned trans, if its a miniature trans theres a possibility that the insulation has broken down over time, there isnt an easy way to test this without special gizmo's.
Hope that answers some of your q's.
Good to see the push is mains rated.

 

[AskerOfGeeks]

Wow You R Really Replying Nicely

look at the voltage rating of the mentioned caps, I bet they are 450v

c3 = 25v
c4 = 16v
rated

I Will Try The Testing Process With In A Few Days And Will Get Back 2 U It May Take Several Days But I Will Get Back 2 U Wit The Results, Whether Its Good Or Bad

 

[killivolt]

Holy hanna, they place the switch in line with 240v........ No offense, but I thought all my UK buddy's are smarter than that, how would you let someone manufacture let alone install this thing

Just replace it, like DP said. With an Isolated low voltage model.

Unless of course you want to modify it to send away any un-welcome strangers

 

[dr pepper]

I thought r1 was 10 ohm, its 10 watts at 1k5 ohm, explains why the rest of the circuit is low voltage.

I'd better shut up now.

 

[AskerOfGeeks]

why r u guys afraid of doorbell switches ?? i never got shocked from doorbell switch in ma life. in our place we all use these kind of switches
http://best-b2b.com/userimg/545/551-1/bell-switch-479.jpg
not push button type.

 

[AskerOfGeeks]

I thought r1 was 10 ohm, its 10 watts at 1k5 ohm, explains why the rest of the circuit is low voltage.

I'd better shut up now.

oh its nothing its just a human error

 

[killivolt]

why r u guys afraid of doorbell switches ?? i never got shocked from doorbell switch in ma life. in our place we all use these kind of switches
http://best-b2b.com/userimg/545/551-1/bell-switch-479.jpg
not push button type.

So, it's an RF module sending it on to the main circuit for the speaker. That would isolate the user

 

[AskerOfGeeks]

So, it's an RF module sending it on to the main circuit for the speaker. That would isolate the user

omg.... no bro.... we are using the same voltage rated "bell switches" (with spring) as the standard switches (used for our normal ac lights) are rated.
the difference between our bell switch and a standard light switch is that bell switch has a spring to return to its off position after being pressed. thats all.... the voltage rating is same for both.. hmm got it ??

 

[killivolt]

omg.... no bro.... we are using the same voltage rated "bell switches" (with spring) as the standard switches (used for our normal ac lights) are rated.
the difference between our bell switch and a standard light switch is that bell switch has a spring to return to its off position after being pressed. thats all.... the voltage rating is same for both.. hmm got it ??

I had a circuit like this one once. Same Transistor a really simple circuit, I was going to use a dead mans switch to activate the circuit and onboard relay. I'm sure it cost's next to nothing once you take the trans out of the circuit.

I thought RF module because a friend of mine has one looks just like it. If I'm correct the way you mount the circuit board and switch isolates the user physically from the line voltage.

Good luck on the repair

 

[AskerOfGeeks]

If I'm correct the way you mount the circuit board and switch isolates the user physically from the line voltage.

Here, This Pic Shows U How I Use The Switch
https://i47.tinypic.com/34jdcw9.jpg

 

[dr pepper]

I've used those before, on door solenoid releases.
Perfectly Ok so long as they cant get rained on.

 

[killivolt]

I've used those before, on door solenoid releases.
Perfectly Ok so long as they cant get rained on.

I didn't say that but, was thinking it.

 

[AskerOfGeeks]

I've used those before, on door solenoid releases.
Perfectly Ok so long as they cant get rained on.

yes rain is a villain but it wont reach the switch until the house fall

 

[AskerOfGeeks]

i dumped that old door bell and bought a new one
problem solved
but will try to fix it one day ( i love electronics its just i dont know it )

 

[AskerOfGeeks]

btb thanks dr pepper

 

[AskerOfGeeks]

likes for all who replied

 

[remon7]

Hi,AskerOfGeeks,
A Step down transformer operating system mainly used in door
bell. Mainly it does not work well lack of AC power (load shedding or power
discontinuous). Tryristor able to make melody doorbell is acts as an electronic
switch.

Capacitor C4 gets charge when switch SW1 is pressed and surge current from
speaker keeps tryristor on. Don’t remake Door bell ckt; you can make this ckt easily
by using new PCB..