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

[DJSUOL]

Could someone tell me how to simulate the clock part in the software? There is no 74hc221 model in the LTspice and how can I use another method to achieve it?

[Carl-NC]

Could someone tell me how to simulate the clock part in the software? There is no 74hc221 model in the LTspice and how can I use another method to achieve it?

Are you wanting to simulate the actual clock circuitry, or simulate the stuff driven by the clock circuitry? If the latter, just use pulse sources and set their timing to whatever you want.

[DJSUOL]

I wanna simulate the design below and try to learn how does it work. However, while I using the LTspice, there is no ne5532, tl072 and 74hc221. I do not know how to continue to analyze it. Have you done the related simulation before and how did you achieve it. I wanna change the circuit to produce 2 delayed clock signal but I do not know how to do it. Thanks for your help.

[DJSUOL]

I also tried to use the LTspice software and Found a model file for NE5532. However, the output of the preamp part is a square wave instead of a clamped signal.

[Carl-NC]

It is useful to simulate the TX and preamp portions in Spice, and see how the flyback & decay respond to changes in the timing or circuit values. You can even introduce a target by using a mutually coupled LR (this shows up in other threads, you'll have to poke around to see).

Once you get to the demodulator (FET switch) the simulation becomes more difficult and hugely time consuming. This is where it's far more useful to just build the thing and play with it in real time.

[DJSUOL]

I need to simulate the circuit to compare with the results of the circuit I built to see if it is correct. But the simulation output from the preamp ne5532 part is different from the practical results. I wonder if you have done a similar simulation before and give me some advice to achieve it.

[green]

I need to simulate the circuit to compare with the results of the circuit I built to see if it is correct. But the simulation output from the preamp ne5532 part is different from the practical results. I wonder if you have done a similar simulation before and give me some advice to achieve it.

A simulation I use a lot. Can add preamp to Tx or Rx. Left click Y scale and change to log if looking at Tx and Rx at same time.

[Carl-NC]

I need to simulate the circuit to compare with the results of the circuit I built to see if it is correct. But the simulation output from the preamp ne5532 part is different from the practical results. I wonder if you have done a similar simulation before and give me some advice to achieve it.

If the TX+preamp simulation isn't agreeing with the actual circuit, then adding the 74221 and demod to the simulation isn't going to help. Maybe post your results and let's see what you got.

I have probably never simulated this circuit, and certainly not the '221. But I have simulated PI circuits all the way through the demods. Using idealized switches and clocks. Models for the 5532 & TL072 are widely available on the Internet.

[DJSUOL]

maybe you can introduce me some other front end design to achieve the same function that you have simulated before? Thanks for your answer.

[DJSUOL]

Here is the ne5532 amplifier model I found and the output from the chip a is a square ware instead of the amplified clamped signal as shown below. In addition, this design from the book introduces to create a 'ground' and compensate the offset signal on NE5532. But when I read the design of Surf or Hammerhead, I found the designs are different. What is the advantage of the book design?

[Carl-NC]

I have simulated the front end of PI-1, it works in simulation. One thing to keep in mind is that C2 can take a while (30ms or so) to settle out. Until it does, the output of the opamp won't look right.

[DJSUOL]

Thanks for your help. But in the practical result, there is no such problem, could you please tell me the reason that cause it in the software? In addition, when I built the circuit with a 12cm diameter, the performance is not very well and it can not detect the coil. Based on your experience, how can I improve it and is it helpful to use two sampling circuit like in the surf PI?

[green]

I have simulated the front end of PI-1, it works in simulation. One thing to keep in mind is that C2 can take a while (30ms or so) to settle out. Until it does, the output of the opamp won't look right.

I haven't tried capacitor coupling to preamp in, hardware or simulation. Added input from PI-1 to circuit above(reply #7). Input capacitor causes an offset but maybe no different than amplifier input offset?

[Carl-NC]

Thanks for your help. But in the practical result, there is no such problem, could you please tell me the reason that cause it in the software? In addition, when I built the circuit with a 12cm diameter, the performance is not very well and it can not detect the coil. Based on your experience, how can I improve it and is it helpful to use two sampling circuit like in the surf PI?

Until you show your results, I have no idea what the problem might be.

[DJSUOL]

Yeah I just do not know why the C2 needs 30ms to be set. In addition, I built the circuit in ltspice. The output of ne5532 is shown and i use a voltage source to produce the delay. However, the result from ne5532 shows that it keeps changing which is strange and after the 1k resistor the signal has an additional square part and the integrator circuit does not output a certain DC level and the output of TLO72 keeps raising. Could you please help me to solve it.


signal pass through 1k resistor
integrator