[SOLVED] Problem in driving Buzzer from transistor BC547

[kunaltg]

Hello guys !!

I am having Weird problem for driving a Buzzer in my circuit !!

I want to implement a RF controlled buzzer (i.e. when remote button is pressed, Buzzer should turn on, & it should turn off when remote button is released)
But in my circuit Buzzer is not switching off once it is turned ON !! My circuit description is given bellow !!! PLEASE HELP !!!!

I am using following circuit with modification to drive Buzzer(using transistor) from RF receiver (Decoder HT12D)

in my circuit R16 is 1Kohm , Q4 is BC547, VCC is 5V !!

I am using this RF module :
**broken link removed**

& RF decoder circuit is like this :
**broken link removed**

Rosc in my circuit is 33K !

D8(pin 10) from this circuit is connected to R16(1K) from Above circuit (First one)

I am using following Buzzer :
http://xhhuaxing.en.made-in-china.com/product/VqJnwsiYAjkI/China-Electric-Buzzer-YMD-12095-G-.html

 

[E-design]

If you disconnect R16 from the chip, does the buzzer stop?

 

[kunaltg]

^ Yes !! It stops after disconnecting R16 (i.e. removing base drive of transistor physically !)

& I have checked my decoder output after without transistor ! Its also working properly (i.e. 5V & 0V respectively with ON/OFF Button position of remote ) !!

 

[hamid159]

make sure transistor should go to active mode to turn off the buzzer

 

[crutschow]

What are the voltages at the decoder output when the transistor is connected?

 

[kunaltg]

@ hamid159 how to make sure ,whether its going in active mode or not ?

@crutschow at the start when button is off ,,Its zero !! but after first turn on ,Its always around 4.5 V !!

 

[hamid159]

just slightly increase R16

 

[amayilsamy]

Put one 10 k resister pull down the base of transister.

 

[kunaltg]

^^ I already tried ,,, no change !!!!

 

[kunaltg]

Anybody there ?? PLease Help !

 

[Venkadesh_M]

Hi what is the source and sink currents of receiver may be you needed to pull up or down.........

 

[kunaltg]

^ I already tried Pull Down resistor !! :-(

 

[Venkadesh_M]

what is the source and sink currents? post data sheet...

- - - Updated - - -

When the output in the wrong case(Buzzing in low input), you tried removing R16 and got buzzer stoped but what is the voltage at the D8 pin after open and before open??

 

[kunaltg]

IC HT12D Typical Source & sink currents are 1.6mA !!
Datasheet :-http://www.botskool.com/downloads/electronics/datasheets/HT12D.pdf

When the output in the wrong case(Buzzing in low input):
voltage at D8 pin Before R16 open :- 3.25V
voltage at D8 pin After R16 open :- 0V

Currently in my circuit, i have shorted Vcc of IC HT12D & Vcc of transistor-buzzer circuit to same 5V battery !!

BUT I just noticed that ,,If i supply transistor-Buzzer circuit with another 5V battery It works like charm !!But i dont want to use another battery ,,i want to run whole circuit from the same battery !! WHat should I do ?? please refer following for understanding :-

 

[Venkadesh_M]

So finaly you can put a diode series with R16 and tell...

 

[kunaltg]

Already Tried !! No success

 

[Venkadesh_M]

Ok now we have to check two things transistor pin connections and the output of HT12D....

- - - Updated - - -

Try this...

 

[kunaltg]

Already Tried !!! No change !!!

 

[Venkadesh_M]

what is the filter cap value??

 

[kunaltg]

10uf 63V !