complete project Circuit diagram

[mschmahl]

Tinkerers schematics

I have some of the schematics, but don´t know how new they are. If I remeber right, than this are the original schematics of tinkerer.

[mschmahl]

and more
I have built it partwise. Some results what I could do on youtube.

It was experimentell with a lot of potential, but I had never a completed detector.

[mschmahl]

more video

[mschmahl]

more...

[Tinkerer]

and more
I have built it partwise. Some results what I could do on youtube.

It was experimentell with a lot of potential, but I had never a completed detector.

These designs had a problem with the inrush current, because there was no inrush current limiting. Under certain conditions this could blow the mosfet gate.

[eclipse]

Here's what I use. It adds some delay and also doesn't produce sparks when you switch on.
Plus overcurrent and reverse battery protection the lazy way.

[waltr]

Wouldn't the ON/OFF switch need to connect to +B to turn on Q3 since +15 is zero when Q3 is off?

[mschmahl]

These designs had a problem with the inrush current, because there was no inrush current limiting. Under certain conditions this could blow the mosfet gate.

You are right. I have blown some mosfet´s...

[Tinkerer]

You are right. I have blown some mosfet´s...

It took me some time to notice the problem, as I was using mosfets with zener gate protection which were quite immune.

[Monolith]

more...

That seems to do a decent job of iron discrimination. If that continuous audio tone was changing in volume when the target is near, it would be less tiring. For myself I would also lower the center frequency a bit. Instead of a center frequency, make it 20% low and 80% high frequency. The iron does not really need to have a great range, it could be more of a yes-no indication.

[eclipse]

There's also hole effect which also may need to be revisited and improved.

[Tinkerer]

There's also hole effect which also may need to be revisited and improved.

Thank you for the observation.

Please tell us more about the hole effect you have noticed.

[eclipse]

On the last post at 0:38 the audio stops for a while when the target is over the coil. It maybe appears when signal is too strong (object too close to the coil)?

[Tinkerer]

On the last post at 0:38 the audio stops for a while when the target is over the coil. It maybe appears when signal is too strong (object too close to the coil)?

The audio pitch or frequency increases for copper or non magnetic targets. For Magnetic/permeable targets, the pitch decreases. There comes the point where the frequency reaches sub-audio frequency, near zero Hz.

The no target frequency should be set at a frequency that is kind to the ear.

A good improvement to the design would be a proportional audio volume.

[eclipse]

On the TX part where the 420R - 1uF(500V) - 47R is located, the 420R resistor is getting quite bit of heat (I'm using 330R/3W there), is this okay or maybe I should lower the value to maybe 100R ? Without those components the voltage reaches nearly 700V with 15V supply and after I soldered them it went down to 450V, which is good, 1uF cap is rated at 500V.