Sallen Key Low Pass Filter, bandpass filter

[Delta Prime]

can you post me a schematic of the working bar type circuit thats cascaded for 20 LED's please?

You've been working so hard I believe you deserve to have either bar or dot mode with a flick of a switch.

LM3914 VU Meter Circuits with Dot/Bar Display & Datasheet

Explore LM3914 VU meter circuits with dot/bar display. Get datasheet, diagrams, and multiple circuit examples ready for your DIY project.

www.eleccircuit.com

PIN 9: The ‘MODE’ pin. If this pin is connected to the V+ pin 3,
(the datasheetdatasheet has the word ‘directly’ in italics),
then the device operates in bar mode,
where the LEDs light cumulatively
from 1 to 10, so that for a given
signal level, all the LEDs before it are lit as well. If Pin 9 is left unconnected,the device operates in dot mode, whereby only the LED representing the level in question is lit, while those behind it &
in front are not lit.

 

[Maglatron]

You've been working so hard I believe you deserve to have either bar or dot mode with a flick of a switch.
View attachment 63113

LM3914 VU Meter Circuits with Dot/Bar Display & Datasheet

Explore LM3914 VU meter circuits with dot/bar display. Get datasheet, diagrams, and multiple circuit examples ready for your DIY project.

www.eleccircuit.com

cool so I've bookmarked that page I am going to read it looks useful but doesn't address the original problem of modifying the circuit with lifted grounds please take another look at it! I want bar graph mode with one input to control the 20 LED's

 

[Delta Prime]

pin 9 is taken to pin 3 on each IC, and a 470R current-limiting resistor is wired in series with each LED to reduce the power dissipation of the ICs.

LED ‘Graph’ Circuits

Here's a variety of practical LED dot-graph and bar-graph analog-value display circuits.

www.nutsvolts.com

 

[Maglatron]

so do you need to put the 470r resistors or are they in built, thanks

 

[Maglatron]

what would the difference be if I used the standard ground connections instead of the ref ground's my thoughts are that the filters run on ref grounds so the out put will be between 6v and 8.4v from the signal from the filter and the standard ground would measure from 0v to 2.4v is that correct?? thanks

 

[Delta Prime]

Stand by Buddy I'm on a stupid phone

 

[Maglatron]

what does that mean? your phone playing up?

 

[Delta Prime]

It means I'm trying to answer your question in detail I haven't abandoned you so just give me a second or two thank you.

 

[Delta Prime]

what would the difference be if I used the standard ground connections instead of the ref ground's my thoughts are that the filters run on ref grounds so the out put will be between 6v and 8.4v and the standard ground would measure from 0v to 2.4v is that correct?? thanks

You're on the right track,you can make your own external voltage divider to make the LM3914 do what you want it to. Because
the ends of the voltage divider terminate at pins which we usually tie to ground & the
reference voltage, we can in fact connect them another way.
If you were to connect an external voltage divider to the RHI pin, you would be setting the
upper limit of the divider independent of the references voltage.
(which you still need to set for the current limit in the LEDs and other functions).
If you were to tie the RLO pin to an external voltage divider as well, you would be able to set
the range of the input, and its upper and lower limits.
This means that you could create a voltage range somewhere in the middle
of a bigger range. For example, if you had a signal that varied between 0 & 12 volts but
you were only interested in the 6V to 9V part of the signal.
Or, perhaps your sensor has a minimum output, say 3V, at its lowest value in the application
you have it in. Connecting external voltage dividers to the
RHI and RLO pins allows you to factor this in.
I got to go to the lab now go to work till the time I have right now I'll see you at lunch

 

[Maglatron]

ok thanks what time is it where you are in the world and one more thing how can I look at the voltage range coming from the filter? occiloscope? see ya!

 

[Delta Prime]

I'm in California it's 5:48 in the morning .I got to be work at 8:00 I normally do some surfing before I go and if I miss my spot in linee to catch a wave it's going to be because of you...

 

[Maglatron]

thanks

 

[Maglatron]

is there any way that I can test the mic-to-pre-amp, amp, filter and buffer before the lm3914 drivers I think they are set correctly because I checked and double checked also changed the R21 to a 4k7 because couldn't find a 500k and the R23 to 0.8meg actually might have been a 470k I will double check it later on

 

[Maglatron]

so I run the sim and the R21 @ 470k resistor seems to run fine heres a screen shot tell me if you need higher resolution picture

 

[Maglatron]

also the resistor of the ref ground circuit is not 4.99k it's 4.6!

 

[Maglatron]

so the C17 capacitor was backwards the resistor R21 is 500k going to dismantal the preamp and put together again also I wired the LM3914 bar graph LED's in bar graph mode too! made sure the mic was wired in correctly which it was when I flick the power switch all led's in the bar graph blink simultaneously, then turn off - not sure if that's just what it does when initializing

 

[Maglatron]

might just build another circuit next to the existing one (mic preamp, amp and reference ground circuit) out of a TL074 and see if makes a difference if I give myself more space next time!

 

[Maglatron]

another question I know how you said that 1 reference ground circuit could be enough for 4 entire filters, I used the 1st refenence ground for the amp filters and the LM3914's should that be ok or should the LM3914's have there own REF GND circuits? thanks

 

[Maglatron]

surfing the web or an actual wave surfing. It'd be cool if you get to surf for a living!!

I'm in California it's 5:48 in the morning .I got to be work at 8:00 I normally do some surfing before I go and if I miss my spot in linee to catch a wave it's going to be because of you...

 

[bertus]

hello,

the lm3914 of the filters connected to the ref circuit can also be connected to the same ref circuit.
that way there will be no offset between the filter and lm3914.

bertus