Dear,
Actually the concept of PI metal detector is that when pulse is given to the coil by the power transistor (IRF740) it will decay soon when pulse ended by timer circuit , but when this search coil comes near any metal object , then the decay time became little greater or pulse will decay slightly later as it is observed in the absence of any object.
this little delay of pulse decaying is detected by circuit,
In Surfmaster circuit ic 555 is kept as a pulse generator ,then signal is injected to IC 14093 & IRF740 .
where IC 14093 trace the signal from IC 555 to IRF740 ( via 2N3906) & manage the switch IC 4066 located after the amplifier IC NE 5534 ,
when the decaying signal from the coil through NE5534 is feed to the IC 4066 ,
this Switch IC (4066) will pass the signal when an other signal is given by the IC 14093
( this IC is looking both signal to IRF740 & IC 4066) ,
The concept is to keep the switch IC 4066 on & off same like IRF740 on & off by timer IC
when IRF740 is near to the OFF stage at the very last tail pulse IC4066 became operational & pass the signal,
then this little signal is than amplified & provided to the speaker or meter .
In Goldpic3 signal to IRF740 & to the IC 4066 switching is kept exactly same as it is kept in the surfmaster design ,
but little programming is done to keep the said idea,
there is no any big secret behind the PIC ,
simple programming,
but if kit is available than you don't have to be worry
BR
Engr Obaid
Linkback: You are not allowed to view links.
Please Register or Login
http://www.thunting.com/smf/index.php/topic,13873.msg88814.html#msg88814
|
|
Logged
|
|
