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Sallen Key Low Pass Filter, bandpass filter

Maglatron

Jul 12, 2023
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let me know though because I'm going on for approximately 45mins in a second! I wa going to use the electrolytic for the 10uf and film for the 100nF1711659675088.png
 

Maglatron

Jul 12, 2023
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no the the 100nf caps I'm using are film type but I was just saying that I have electrolytic ones in the box I bought I do remember you saying that the 10uF ones on the REF GND circuit would be fine though!
do you remember saying that I could use electrolytic caps for the 10uF REF GND circuits?
 

bertus

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Nov 8, 2019
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hello,

the value of r4 is not critical.
you can use either value there.
there are even circuits around where there is a short in stead of the resistor

bertus
 

Maglatron

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4k7 it is working on it till 12 it's 10:40 here now so if you guys have anything to say while actually working on it that would be great!!
 

Maglatron

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resuming later just have to put the amp on the first TL074, done the REF GND circuit and 1 resistor away from finishing the pre-amp so going good using the colour code aswell! pics later! thanks
 

bertus

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hello,

yes, that is fine.
the gain will be 5.1 in stead of 5.0.

bertus
 

Maglatron

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cool so tested the REF GND part of the circuit and its as sweet as a nut measureing exactly half the input voltage eyes were getting really tired at the end of that session almost like soldering in the dark still took pics for you!! the strangly yellow wire is the out put to the filter which I will start on the filter and buffer as soon as my eyes are working properly again, perhaps tonight, thanks and the soldering is not too shabby either
 

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Maglatron

Jul 12, 2023
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also tested the LM3914's with the positive and negative connected but the REF GND and signal not yet connected (because I've not re-made yet) but the good thing is they're not getting hot so that is a positive but thinking about making that circuit again because soldering wise it looks a disaster (although I do think it's wired right!)
got confused I didn't test the LM3914's yet but I intend to, was thinking of doing it and somehow thought I did it already my mind's not what it used to be!
 
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Maglatron

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actually I'm not certain if I did or did not! I will do it next time round! thanks is there any way of seeing if the pre-amp and amp is working before proceeding to making the filter part for the first column LED cicuit?
 

bertus

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hello,

you could connect the preamp directly to the peak detector circuit.
that way you will see all signals going into the microphone on the display.

bertus
 

Maglatron

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HAPPY EASTER!!! in this schematic there are effectivly two 10uF caps going from the negative to positive is this okay or should I just use one??!!!??1711905189337.png
 

bertus

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Hello,

Decoupling capacitors are place close to the power lines of EACH chip.

Read this thread on AAC for more info:

Bertus
 

Delta Prime

Jul 29, 2020
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The 2.2 microfarad solid tantalum or 10 microfarad electrolytic are nominal values,you may need more; to avoid oscillation on each LM 3914 you use for your application in addition to recommended lead length to LEDs... I know you're going to bookmark this, that's okay.
I think this is page two of the datasheet.
photo_1711907602900.png
 

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Maglatron

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I will take some more pics of my progress hopefully works well this time round all connections so far are good just need to make the buffer circuit out of the BAT43 diode and the 100nF cap and the 1meg resistor and the op amp wire it up and have a look and see, wish me luck!! oh yeah and what I was saying before about plugging the LM3914 chips to the power without the signal or REF GND connected the chips didn't get hot so I think that that part is ok so far. Going to take pics as soon as I can, thanks
 
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Maglatron

Jul 12, 2023
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Hello,

Decoupling capacitors are place close to the power lines of EACH chip.

Read this thread on AAC for more info:

Bertus
my internet won't let me access the site! it's ok went through the search option on the site instead of the link I'm on it!
 
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