anyone built the EPE microcontrolled detector?

[John Smith]

I am still trying to decide what to build as my intro to this hobby, and I had a look at the metal detector by Mark Stuart from the EPE mag.


While it looks OK, there seems to be an error in the circuit and the PCB layout. Has anyone built this unit ?


The "set tone " control would hardly have any effect ( trying to alter the DC of the low impedance output of an op amp through a 100Kohm resistor )


I think the bottom end of R3 should go to pin 6 of IC2a, rather than the output pin 7.


John

[Carl]

Re: anyone built the EPE microcontrolled detector?

>I am still trying to decide what to build as my intro to this hobby, and I had a look at the metal detector by Mark Stuart from the EPE mag.


>While it looks OK, there seems to be an error in the circuit and the PCB layout. Has anyone built this unit ?


Mark Pauls who provided the PIC code, he may know of others. I think several others have built the Proscan PI detector. It might be a little easier since there's no microcontroller to deal with, but it also has a little less flexibility.


>The "set tone " control would hardly have any effect ( trying to alter the DC of the low impedance output of an op amp through a 100Kohm resistor )


>I think the bottom end of R3 should go to pin 6 of IC2a, rather than the output pin 7.


I took a quick look at this and tend to agree - VR1 will do nothing in this configuration and should do what's intended if R3 goes to pin 6.


- Carl