Sallen Key Low Pass Filter, bandpass filter

Maglatron

Jul 12, 2023
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I've tried turning the pc on and off, no joy, I have a question what exactly does this little buffer do? the same thing happens it just stop just shy of 720ms, where ever I put the probe, whats up with that?1702229384244.png
 
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bertus

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Hello,

The buffer has a high input impedance, so the detector is not loaded.
The buffer output has a low impedance to drive the LM circuit.

Bertus
 

Maglatron

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Hello,

The buffer has a high input impedance, so the detector is not loaded.
The buffer output has a low impedance to drive the LM circuit.

Bertus
my simulator stops just before 720ms wherever I put the probe so I do not think it is my computer crashing do you know what could be the cause?? this mean anything
1702230724159.png
 
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bertus

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Hello,

I am trying to setup LTspice again to have the LM in the simulation.
I am using LTspice in wine on my linux PC.

I seem to be missing the .sub file of the LM3914.

Bertus
 

Maglatron

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when I run an older schematic it works fine this is really puzzling me
 

Maglatron

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ok I'll be there when you get back see if you can solve this 720ms conundrum
its actually 691.8 stops dead every time1702232342934.png
 
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Maglatron

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also can somebody alter the Pre-amp to run on 12v if you're able
 

Maglatron

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I re-installed too - to fix the 720ms problem and I've lost a diode (the one I was using) not a major problem but it's not good, and its even worse only makes it to 90ms
 

Maglatron

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the middle one works fine the filters on the otherhand do not!!1702237188022.png1702237363111.png
 
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Maglatron

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can you solve the problem with the black box not going on for long enough and it takes extra long to load aswell! maybe something to do with this. I can't work it out!!! it's bugging me1702238286753.png
 
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Maglatron

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Hello,

I am trying to setup LTspice again to have the LM in the simulation.
I am using LTspice in wine on my linux PC.

I seem to be missing the .sub file of the LM3914.

Bertus
Did you manage?!? also wav file is fine! I don't know whats wrong, please help
 
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Maglatron

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Hello, I looked through the info but there is nothing about setting the time that the black box duration is for, I don't know how to set it so that it works again
 

Harald Kapp

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there is nothing about setting the time that the black box duration
which black box? Do you mean the simulation window?
maybe something to do with this.
No. This box in post #536 is the dialog to set the horizontal plot axis. It haas absolutely nothing to do with the simulation per se, it is used for displaying the results only.
the middle one works fine the filters on the otherhand do not!!
The images are hard to read, but it looks like you left one input of the opamps open. See this example with my markings in red:
1702294710581.png
An opamp always needs both inputs connected somehow. How this "somehow" looks depends on the circuit.
Or is that a connection to a mid-voltage reference? As stated before: hard to read.

can you solve the problem with the black box not going on for long enough
Do you get any error message?
LTSPICE, as any SPICE based simulator, does not (can not) solve the network analytically. Instead it does a numerical approximation of the voltages and currents over time. To do so it uses numerical integration in discrete time steps and checks for convergence of the results. If the results do not converge well, the simulator decreases the time step and repeats the calculation. If for whatever reason the sumulation does not converge well, the time stepps become increasingly smaller and the simulation time increases accordingly. This may be the case here.

In the resource section I linked, specifically in this thread, I show some things you can try to improvethe situation / remedy the issue.
 
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