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Sallen Key Low Pass Filter, bandpass filter

bertus

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Hello,

Do you have a scope?
Other way is to see how the signal shows at the LM3914's.

Bertus
 

Maglatron

Jul 12, 2023
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ok cool I do have a chinese scope cost £430 not used it a whole lot but I think I prefer the method on the latter like stated before i'll do a channel at a time! thank you!
 

bertus

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Hello,

Here is a PDF on how to use a scope.

Bertus
 

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Maglatron

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So on the first board, I'm putting the pre amp, the amp, and a REFGND buffer circuit for the amp, because the amp has got a REF ground, so thats 3 of the 4 op-amps in the TL074 so thats covered the first bit of the project! thanks for the PDF BTW
 
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Harald Kapp

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there are some arbitrary numbers do I just round them to the nearest whole number of resistor that is in the kit of resistors or sholud I mix the values to arrive at the correct values??? intuition tells me to mix!
For a precision circuit you would use series and parallel connected resistors to arrive at the "exact" value. But bear in mind your application: a visual display of the spectrum of an audio signal. Nobody, absolutely nobody will notice when your filters are off the "exact" parametes by a few %.
Also bear in mind that you use 5 % capacitors. These will contribute much more error than your 1 % resistors.

Long story short: round the values to the next in the E96 series.
 

Maglatron

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For a precision circuit you would use series and parallel connected resistors to arrive at the "exact" value. But bear in mind your application: a visual display of the spectrum of an audio signal. Nobody, absolutely nobody will notice when your filters are off the "exact" parametes by a few %.
Also bear in mind that you use 5 % capacitors. These will contribute much more error than your 1 % resistors.

Long story short: round the values to the next in the E96 series.
Nice one thank you it's coming together, slowly slowly!
 

Maglatron

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Built the preamp and the amp and the buffer REF circuit for the amp next comes the first of the filters and the envelope detector, will have picture soon! because the filters have three stages and then an envelope detector I'll be using one chip, TL074, for each of these, BAT43 diodes have come and the so have the capacitors waiting on the resistors I have loads so I will see what I have to see if I can build the first filter!
 

Maglatron

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Resistors have now arrived, will be working on it at the soonest possible chance!
 

Maglatron

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I want a watt meter any good ones tthat you guys know of to add to my toolbox?
 

Maglatron

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sorry for misplaced topic, could you move my post to the correct appropriate forum please?
 

Maglatron

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here's the display progress is slow but still progressing!
 

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Maglatron

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did you mean to post in the help with IR2110 chips forum thread, if so it's a cool ida but I've ordered an analog meter so going to do that just because I'm not getting a compass
 

Maglatron

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just to clarify because not been concentrating on this project for a while, I know that I don't build the part in red, but do I build up untill after the 10uF C17 cap and this is where all of the filers are wired in? thanks going to get on with it very soon, I have been concentrating on the wheel project! and assume the ground of the mic just connects to ground?
preamp_comment.png
 
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Maglatron

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also I have a couple of these spice models, for R23 should it be 820k or 15k? thanks I think the image/shematic is correct with 15k
1709406010919.png
 
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Maglatron

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I have a model where the resistor of the R23 is 50k so just wanted to know if the first thought of 15k will do? thanks, back on this part of the project till I have the parts for the maglatron 2.0 :)
 
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bertus

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hello,

the value of that resistor could be lowered when we adapted (raised) the values of the coupling capacitors.

bertus
 
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