PI metal detector with energy recuperation

[deemon]

First, and most important one, almost “textbook” definition of PI is that it takes sample when all initial pulse energy is either dissipated or recovered by some mechanism, so no stored energy exists in system, except one stored in target. This one is completely different, taking sample during period when energy is still present in coil circuit (and recovered later). At first glance, looks like eternal source of trouble, but interesting idea, worth investigating. Achieved using complex substraction circuit. Second, this design takes coil current as a signal, not voltage developed across coil, very interesting solution. (I tried something along these lines before, but unsuccessfully, more or less).

Yes , the main idea was to "catch" a target response when the current is still in the coil . Here we have 2 advantages - doubling the target response with the same coil current , and "stabilizing" the coil after flyback pulse . You see , in a conventional PI devices ( with voltage coil output ) we can have a problems with coil "ringing" ( due to parasitic resonances ) , parasitic voltage signals on the coil , so we need to shield it .... but here - everything is quite different , we make a half-sine flyback , and short the coil - that's all . Coil is shorted , so all the ringing and "electric" part of EMI goes away , but the target signal is still receiving - and we get the signal in the current form , via the current trans . And another advantage - finite duration of the flyback pulse ( no more this annoying exponent "tail" ) , and after it - only a constant current in the coil , that cannot disturb our received signal - it can be useful for the better target discrimination . You see , now we don't need to wait when the coil energy is dissipated - we can have a signal immediately , just after flyback is finished .

I just watching schematics and trying to figure out how it works.

Of course , I can explain all the circuit , stage by stage .... but I need to write more text , it needs a time . By the way , in this circuit are "hidden" some very interesting solutions ...

[deemon]

This is not what Arzamas16 does with energy recovery:

Yes , this Candy's idea is completely different .... and Johnson's idea too . It's enough to look at the coil current shape .

[deemon]

It has a drawback, though. The power recovery process slows the return of the coil current to zero. The consequence is that targets with fast Tcs are not energized as well as with a system that doesn't have the power saving feature.

His idea has a drawback , but not mine He needs a time to completely stop the coil current , because he uses a voltage signal pickup . But I use a current pickup - here is a main point

[moodz]

His idea has a drawback , but not mine He needs a time to completely stop the coil current , because he uses a voltage signal pickup . But I use a current pickup - here is a main point

... and you may have a problem that I have already patented your technique

[deemon]

... and you may have a problem that I have already patented your technique

Really did ?

[Aziz]

... and you may have a problem that I have already patented your technique

Were you faster than Candy?

Aziz

[WM6]

Were you faster than Candy?

Aziz

Moodz Lab on the horizon.

[moodz]

Moodz Lab on the horizon.

...back to energy recuperation .... There was a idea put forward by a guy with the handle Muntari a while ago to utilse the fly back energy to power high intensity LED lights focused on the coil head. Target information from the processor would modulate the color and intensity of the light as a heads up indicator as addition / alternative to using audio feedback. Could be useful at night or under water also.

[mikebg]

... and you may have a problem that I have already patented your technique

I tested the Moodz's idea for ASinc pulses train technology. It operares very efficient with a simple PFN (Pulse forming Network) - no need to recuperate energy. Fortunately the ASinc train technology is not patented yet.

[Tec]

Hi Deemon,

That is a masterpiece of discrete components the likes I which I never thought possible, it is an inspiration to me.

If you can design that, then working with discrete components like an INA126 or a micro like a 'PSOC' will be super-easy for you.

You will be able to replace oscillators, and amplifiers with single IC's

Hand soldering SMD is easy also, especially if you can assemble that.


My thoughts on Energy capture, good idea.

Note the target responds to the Change in magnetic field. or Delta-I in the coil.

It must decay quickly (change quickly).

Perhaps you could store the energy as a high voltage, and then bleed it off.

But allowing the current to continue to circulate through a low-resistance path, prevents it from decaying quickly and 'hitting the target'..

Tec

[deemon]

Note the target responds to the Change in magnetic field. or Delta-I in the coil.

It must decay quickly (change quickly).

Perhaps you could store the energy as a high voltage, and then bleed it off.

But allowing the current to continue to circulate through a low-resistance path, prevents it from decaying quickly and 'hitting the target'..

Tec

Of course , a quick current change rules . If the current rapidly changes from +I to zero , we have a target signal . But when the current changes from +I to -I , we have a twice signal , that's the only difference

In another words , if we have a rapidly changing magnetic field near the target , changing from +2*B to zero , then our target gives its response . But what if we apply a constant field -B to the target ( from a permanent magnet , for example ) and repeat our pulse ? The field would change from +B to -B , with the same target signal . It's exactly what we can see in my device ....