[SOLVED] Problem in driving Buzzer from transistor BC547

[Venkadesh_M]

replace the buzzer with a LED what happens??

 

[kunaltg]

Same thing happens with led Also !!

 

[Venkadesh_M]

I thought some EM interference created by the buzzer affects the receiver but that is not the case, then If we left it open it works fine itf we load it then it latches in the high state, but works fine with separate supply...
Measure the high output without load and with load it is 3.25V as you said..

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remove the free wheeling diode...

 

[kunaltg]

I removed the FWD !! & High Output without load is 5.15V same as my VCC

 

[Venkadesh_M]

You are loading 3.25 - 0.7 / 1k that is 2.5 mA so replace the 1k with 10 k that is enough driving a buzzer...

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Do you having a 74 04 ???

**give the output through 74 04 and try with a L E D in sink mode...

 

[kunaltg]

I already tried with 10K base resistor ! No LUCK !!!!

I don't have 7404 !! & i don't want to increase size of my circuitry much !! As this is a very basic circuit ,,,but i don't understand why it is not working !!

 

[Venkadesh_M]

we are not going to increase the size of the circuit we are going to find the reason why Its happening Do you having a 555 IC ?? what is the power source and how do you getting 5V?

 

[kunaltg]

ohhk ! I am having 555 IC !! I am Using a 9V battery & 7805 for getting 5V !!

 

[Venkadesh_M]

Ok hold the 555IC thing now I thing the problem is your power supply side....

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measure the 7405's output when the buzzer is ON state(error case).. It may 3.25 V and allow buzzer to sound and Ht to work but not the receiver to receive!!??

power the receiver only in different power and link the gnd and check the operation....

 

[kunaltg]

I already tried my circuit by supplying from another 6V battery without 7805 !! No change ,,same behavior !!

 

[Venkadesh_M]

did you measure the output voltage of 7805 when buzzer is on state??

 

[kunaltg]

Sorry !! It is 4.20 V !!!

 

[Venkadesh_M]

ok now get the 555 IC and give Vcc in 8 gnd in 1 and connect 2&6 to give input connect the LED in 3rd pin and check it out...

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can you post a snapshot of your circuit??

 

[kunaltg]

I tried using 555 as u said !! LED works properly with it !! But buzzer does not ,, !!

Currently i have implemented this circuit partially on bread board !!

 

[Venkadesh_M]

Then two reasons possible one is inability of power source for buzzer or magnetic interference caused by buzzer affects the receiver signal....

But doesn't work with
**Transistor LED configuration**
and 555 buzzer configuration??!!
so the possible cause is power supply or some weak connections......

so better try buzzer with 555 with a single source, in a source which has lot power to deliver like a RPS but not a battery..
using a 7805 in a 9V battery may not give you 5V all the time and with a 6V source the max output can be 3V only....

 

[kunaltg]

"6V source the max output can be 3V only" HOw ??? I connected 6V battery directly to my circuit not through 7805 !!

 

[dick_freebird]

Mechanical buzzers are filthy little EMI makers. Maybe you
want to swap it out for an indicator LED, just to get the
rest of it right. Then, consider moving to (say) a piezo
type? Or trying harder to snub all the contact chatter
that the buzzer may be making (maybe spend more effort
on filtering the control IC supplies, etc.).

 

[kunaltg]

But i dont think its a Mechanical Buzzer !! Its a Piezo type only !!

 

[Venkadesh_M]

I am coming to the point you have to make sure the following things once again....
1, not working with 555 and buzzer
2, not working with Bc547 and LED
3, working with 555 and LED

and let me tell two possible reasons for it....
1, If you sure its not working with transistor and led combination then its sure not problem of EMI
2, The possible reasons for latching could be loading power supply or loading decoder
you know how it happens,
first of all the circuit works fine but if you turned the buzzer or led ON it loads something and after that the circuit working no more thats why it may be latched in the same state...
still you not talked a word about powering and placing of transmitter side.......

 

[kunaltg]

Points 1,2,3 are correct !!

Its not problem of EMI !! Because HT12D has 4 data outputs ,,while in latch conditions other data outputs work properly !!

I didn't talked about powering & placing of transmitter , because its working properly !! Currently i have implemented it on breadboard only !!

Will it work ,if i replace BC547 with any Mosfet ?