Simple door bell circuit with speaker . . .help

[Rickkh]

I am trying to get my circuit to sound a 8 ohm speaker for 5 seconds (500hz sound).
Am I right in what I've done? Can someone explain the R C calculations and setup to get 5 seconds. I am trying tio get my head around it.
Thanks.
Will one of these circuits suit such a simple application?
Its annoying me, I think I am just getting confused. I simply want to make a speaker squeal at 500 hz for 5 seconds....I hope you can help.

 

[ericgibbs]

hi,
Look here: https://www.unitechelectronics.com/NE-555.htm

There are lots of applications to be found using Google.

 

[aljamri]

Thanks

hi,
Look here: https://www.unitechelectronics.com/NE-555.htm

There are lots of applications to be found using Google.

Thanks ericgibbs for this usefull site.

 

[Rickkh]

I think I have to set a monostable up for the time aspect (5 seconds) and an astable for the frequency. I want the circuit to be real so is this circuit right or will the speaker not work?
What values are practicle (for nonostable 5m resistor and 1microfarad cap) and astable ( 2 x 1k resistors and 1 microfarad cap)?????

 

[kchriste]

You should use a monostable for the 5 second timer. Here is a value calculator:
**broken link removed**
And for the tone frequency (Scroll down a little):
**broken link removed**
Here are some examples of what could work for your doorbell:
**broken link removed**

 

[sekurustew]

door bell

i am also doing the same doorbell project my speaker is continously ringing when its suppose to ring for only 5secs .what could be the problem? I have selected my monostable 100k resistor and 45micromfarad cap and astable 2.7k and 4.7 k resistors with a 0.15 micro farad cap.

 

[colin55]

Here is the circuit:
**broken link removed**

It is not suitable for battery operation as the 555 IC's are connected to the supply and draw current at all times.

 

[sekurustew]

thanks very much .so are you saing i cannot set up this project at home using a 9v battery source

 

[MrDEB]

not cosiure but you could just short the push button and have the doorbell button turn the power on and off.
would need another 555 to hold the power on while the doorbell rings.
look at using the 7555 = cmos version= less power.

 

[colin55]

If you want to use a 9v battery, here is the circuit:
**broken link removed**

 

[MrDEB]

Colin55, you stole my idea!!

LOL
would still use the 7555

 

[colin55]

It's pointless using the 7555 as the 555 takes only 10mA out of the 100mA and it only operates for 5 seconds.

 

[MrDEB]

when using a battery every ma counts

the 555 = 10-15 ma supply current
7555 = 60-300ua supply current if I am reading the data sheet right??
at ua the unit could be powered up all the time then the timer doesn't need to reset itself every time the button is pressed.
just my opinion.

 

[colin55]

9v battery = 100mAH 300uA = 300 hrs = 15 days!!!!

 

[MrDEB]

good point
use AAA batteries?
wonder why if attached to a house the op doesn't use a transformer/ regulator power supply??

 

[audioguru]

A Cmos 555 has very low output current when its output goes high so it would need an amplifier or a transistor or two to drive a speaker.

An ordinary 555 will have an output current that is too high if it drives an 8 ohm speaker.

You don't want a square-wave feeding a speaker as a door bell because it sounds awful.

 

[Mikebits]

You don't want a square-wave feeding a speaker as a door bell because it sounds awful.

Reminiscent of a few females I have known in the past.