how to simulate a PI metal detection in the software such as ltspice

[DJSUOL]

In your design, have you improved something of a modern commercial product?

[dbanner]

Read hammerhead document, excellent for understanding.

[waltr]

Perhaps you should focus more on reading through the forum and doing more experimenting.

Also my recommendation. It is how I learned about how these PI detectors work.

Read hammerhead document, excellent for understanding.

Yes, the original HH article is excellent and was my go to reading when first prototyping the circuits.


And As I and Carl has stated:
LTSpice and ALL circuit simulators have HUGE LIMITATIONS.
Simulate PARTS of the circuit as Carl suggest. He knows since he has worked professionally in electronics for many years.
This is the way we as professionals design and simulate circuits.

The second part is then BUILDING the circuit and measuring to see if the simulation is correct and then mod the sim circuit to act like the real circuit.

It sounds like this is a school/university project. Is it?

[DJSUOL]

YES. This is my final year project.

[DJSUOL]

I built the surf PI circuit in the ltspice and I got a NE5534 model from the Internet. However, the output of NE5534 is just a square wave. Could you please tell me the correct output from it?


If the model is wrong, Do you have the method to implement it?

[waltr]

I built the surf PI circuit in the ltspice and I got a NE5534 model from the Internet. However, the output of NE5534 is just a square wave. Could you please tell me the correct output from it?
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If the model is wrong, Do you have the method to implement it?

What doe the 555 output and MOSFET Gate look like??

What does the Node between L1 & R8 look like???
Remember that op-amp is set to a gain of 1000. If coil output looks ok then try decreasing the op-amp gain a lot.

If unsure of NE5534 model try another op-amp for the LTSpice lib. The LT6230 works well.
Did you learn any circuit troubleshoot techniques?
These need to be applied even to a simulation. Start at circuit beginning and check each signal.

Also the simulation circuit may need to be simplified.
Here is a circuit that simulates that you can play with.
Coil_pulsingIB-Interg.zip

[Carl-NC]

And why the output from ne5532 should be 2.5V?

Sorry, I made a mistake. It should be 1/2 the battery, or about 4.5V. I usually work with 5V supplies.

I think the designs of surf PI and Hammerhead are similar. What I mean is that can I add an Rx coil for the surf PI and if I use a 12m diameter coil, will it work well? Finally, can you tell me about your WT design? Have you designed some multiple zone type ones? For PI-1 design in the book, why it creates a ground and adds a circuit for NE5532 IC1A pin- to compensate the offset?

The Surf PI isn't set up to take a separate RX coil. You could do it with some effort, and it would work just fine.

Yes, the WT design has 6 zones.

It is to compensate for offsets and settling errors. There are different ways to design the front end, in this one I was just trying to avoid the complexeties of weird power supplies.

I built the surf PI circuit in the ltspice and I got a NE5534 model from the Internet. However, the output of NE5534 is just a square wave. Could you please tell me the correct output from it?
If the model is wrong, Do you have the method to implement it?

I agree with waltr. If the 555 circuit is giving you the right pulses, then check the inductor. Does its wavefor look correct? What about the waveform at the diode clamps? Is the opamp powered correctly, is the comp circuit OK? Reduce the gain to 10, then try 100. Etc etc. This is basic stuff. It looks like you're trying to go straight to the end.

[DJSUOL]

For the 6 zone system, how can the WT identify if the object is in left or right?

[Carl-NC]

There are 3 RX coils on each side, the RX coil with the strongest signal is the zone that gets indicated.

[DJSUOL]

Could someone tell me what is the offset potentiometer function?When I adjust it, the exceptionally decayed part exceeds 0 V.

[DJSUOL]

1.pdf