Maker Pro
Maker Pro

Sallen Key Low Pass Filter, bandpass filter

Maglatron

Jul 12, 2023
1,567
Joined
Jul 12, 2023
Messages
1,567
?? please can you recommend a resistor to use I'm going to get cracking
 

Maglatron

Jul 12, 2023
1,567
Joined
Jul 12, 2023
Messages
1,567
which ones are the coupling capacitors,? the ones in the filters that where wrong by uf and nf?
 

Maglatron

Jul 12, 2023
1,567
Joined
Jul 12, 2023
Messages
1,567
I'm going to go and read back through the thread, see if I can find answers
 

Maglatron

Jul 12, 2023
1,567
Joined
Jul 12, 2023
Messages
1,567
I can't find the post that told me that the value of the cap was wrong in the sim where you helped fix the design!
 

bertus

Moderator
Nov 8, 2019
3,366
Joined
Nov 8, 2019
Messages
3,366
hello,

have a look at post #625 where i changed the capacitor value.

bertus
 

Maglatron

Jul 12, 2023
1,567
Joined
Jul 12, 2023
Messages
1,567
okay found it so now that that is changed to 10uF what should R23 be please? thanks!
1709568892597.png
 

Maglatron

Jul 12, 2023
1,567
Joined
Jul 12, 2023
Messages
1,567
I made a start I soldered the bar graph leds on but nothing else yet! kinda got side tracked with another project! I'm back to this now though! thanks!
DSCF0215.JPG
 

Maglatron

Jul 12, 2023
1,567
Joined
Jul 12, 2023
Messages
1,567
so I have finnished reading the entire thead, I made a start I soldered the bar graph leds on but nothing else yet! kinda got side tracked with another project! I'm back to this now though! thanks! as you can see the 45Hz image uses a 15k resistor for R23 and the 7000Hz uses 820k I want the resistor to be the same value which value would you choose? thanks also can't get the envelope detector working again?
7000Hz
View attachment 62943

7000Hz

1709576479319.png

45Hz
1709576517426.png
 

Maglatron

Jul 12, 2023
1,567
Joined
Jul 12, 2023
Messages
1,567
look and see! if you can find fault! thanks
 

Attachments

  • 45Hz.asc
    310 bytes · Views: 0
  • 7000Hz.asc
    16.6 KB · Views: 0

Maglatron

Jul 12, 2023
1,567
Joined
Jul 12, 2023
Messages
1,567
the filters are working in a fashion but don't produce much voltage change (less than 0.1 of a volt0 from what I understand they need to vary by 2.4volts! need some adjustments can you fix it ??
1709578359972.png
 

Maglatron

Jul 12, 2023
1,567
Joined
Jul 12, 2023
Messages
1,567
Mr Bertus maybe? you were good with this last time! I have refreshed myself with the details today but a little stuck, thanks last time you also changed the R12 from 42.2r to 42.2k aswell and I remember that making it work better!
 
Last edited:

Martaine2005

May 12, 2015
4,957
Joined
May 12, 2015
Messages
4,957
Didn’t you take notes (written)?.
Bad move.
This is not a telephone conversation with forum members.
Read the thread again! All the information is there.
If Mr Bertus remembers, I’m sure he’ll reply, but if not, it’s up to you to find that information that has also been told to you more than twice.
 

Maglatron

Jul 12, 2023
1,567
Joined
Jul 12, 2023
Messages
1,567
ok getting somewhere
Hello,

When pin 8 is gounded the reference voltage will be about 1.25 Volts.
When pin8 is lifted with a resistor, the reference voltage will be higher.
Have a look at the formulas again.

Bertus

Hello,

Why do you want such high values?
Audio is not so high.
The 2.4 volts range is already quite high.
You might even need an amplifier between the filter and rectifier.

Bertus

Hello,

In stead of making a complete series of filters twice, you could add a simple amplifier between the filter and rectifier circuit:
View attachment 61950
That would save you a lot of work.

Bertus

Hello,

Now you have R13 at 4K7 and R23 at 165K.
Change that to R13 at 27K and R23 to 1Meg and see what happens with 45 Hz and 7000 Hz.
With those values C14 will have a factor of 6 less influence on the frequency dependend gain.

Bertus
I changed the R23 resistor to 1meg and on the 7000Hz circuit the signal reaches 8.7v at the top and 6 at the bottom so this is good, now waiting for the program to run and I will screen shot it and do the same for the 45Hz one too!
running the 45Hz now... and it reaches similar voltages!!!
1709580480674.png1709579947929.png
 

Maglatron

Jul 12, 2023
1,567
Joined
Jul 12, 2023
Messages
1,567
yes I took notes when reading it back through it on paper and I'm getting there it was a couple of months back will remember to take notes in future!!! thanks
Didn’t you take notes (written)?.
Bad move.
This is not a telephone conversation with forum members.
Read the thread again! All the information is there.
If Mr Bertus remembers, I’m sure he’ll reply, but if not, it’s up to you to find that information that has also been told to you more than twice.
 

Maglatron

Jul 12, 2023
1,567
Joined
Jul 12, 2023
Messages
1,567
looks complete now with a couple of adjustments to get it in the 2.4volt range with trial and error on the R23 resistor and I'll crack on!! thanks everyone!! seems to be 0.8meg!
 
Last edited:

kellys_eye

Jun 25, 2010
6,514
Joined
Jun 25, 2010
Messages
6,514
There's 'bugger all' to the basic design of the filter section that couldn't be actually, physically constructed (on protoboard or hardwired) with sockets for the relevant resistor/capacitor values and you could play to your hearts content until you found something that worked.

How about building ONE channel that actually works?

It would be a damned sight quicker than a 700+ post regime and save some members time too.

It would also be nice for those who have taken the time and effort to assist in this thread to see something PRACTICAL from all their input. A few displays on some board doesn't cut it.

And if you haven't got a grasp of it by now then you need to reconsider your approach.
 
Top