pin pointer

[sinclairuser]

hi all, i built the off resonance pin pointer out of the book ITMD, i triple checked everything but could find no fault with my work,but all i get is a constant flashing led, adjusting does nothing it was built according to the plan in rev1, is there an errata for this project that i missed.when i measure inductance on my coil it changes when metal is present, so the coil is working, it has power where it should and is producing a half sine so i'm a bit lost.

[sinclairuser]

hi all found a couple of threads about pinpointer, so have a plan of attack, i will post what was wrong and what was the cure.

[Qiaozhi]

hi all, i built the off resonance pin pointer out of the book ITMD, i triple checked everything but could find no fault with my work,but all i get is a constant flashing led, adjusting does nothing it was built according to the plan in rev1, is there an errata for this project that i missed.when i measure inductance on my coil it changes when metal is present, so the coil is working, it has power where it should and is producing a half sine so i'm a bit lost.

Do you have the first or second edition of ITMD?

In the second edition a small change was made to the circuit where R1 (Q1 emitter resistor) was replaced with a 5k trimmer. This provides an adjustable bias to allow for component tolerances. In some builds with the original circuit, the oscillator would sometimes fail to start.

[sinclairuser]

Do you have the first or second edition of ITMD?

In the second edition a small change was made to the circuit where R1 (Q1 emitter resistor) was replaced with a 5k trimmer. This provides an adjustable bias to allow for component tolerances. In some builds with the original circuit, the oscillator would sometimes fail to start.

first ed, thanks Q.