hello ^^

i'm working on this video ....
The buzzer is continuously beeping even with no metal near the coil and even without the two coils XD
what should i do ?

 

If you want it to stop buzzing...
Option 1) remove the battery.
Option 2) remove the buzzer.

Or

Post the circuit diagram for further assistance....

 

Hello,

Please post the schematic.
Also at wich frequency do the oscillators work?
RF and a breadboard are not a good combination.
The strips inside the breadborad will make capacitors that will influence the working.

Bertus

 

http://www.easytreasure.co.uk/bfo.htm

 

bfo types require that the frequencies of the two oscilators be the same. there are no trimmer caps on that circuit to vary one to "ballance" the circuit. they work by changing the inductance of the search coil with the burried metal, changing its frequency a bit, causing a hetrodyne that is amplified by the rest of the circuit.

 

Hello,

It looks like the circuit in this link:
http://chemelec.com/Projects/BFO/BFO.htm
Here is info on the used PCB, from that site:
http://chemelec.com/Projects/BFO/BFO-3.jpg
You can see there is a fixed coil (220 μH) in the picture and a would coil as receiver coil.
The coils must have about the same inductance to have the circuit working.
When they are to far off the speaker will keep a beep tone.

Bertus

 

Option 1) remove the battery.
Option 2) remove the buzzer.

Option 3) remove the phone (which contains metal).

 

bfo types require that the frequencies of the two oscilators be the same. there are no trimmer caps on that circuit to vary one to "ballance" the circuit. they work by changing the inductance of the search coil with the burried metal, changing its frequency a bit, causing a hetrodyne that is amplified by the rest of the circuit.

In the home page of this circuit they say that the second coil is trimmed with a brass nut around the coil.