Sallen Key Low Pass Filter, bandpass filter

[bertus]

Hello,

In the simplest schematic of the datasheet the leds will show from 0 - 1.25 Volt:

Bertus

 

[Maglatron]

Oh i see so if I set 4 low (Rlo) and 6 high (Rhi), then the voltage to turn on one LED at a low voltage, but will illuminate them all - at rellatively high voltage ie 1v lights 1 LED and 9 volt lights 20 LED or if you set the pins closer then the number 1 LED would turn on at 2v, and then light the 20 LED with 3v is that correct? and how does this relate the the signal on pin 5

You can set the sensitivity of the LM3914 or LM3915 by changing the Rlo (pin 4) and Rhi (pin 6) voltages.
The Rlo will set the lowest led and Rhi will set the highest led.

not sure I understand this!

 

[bertus]

Hello,

When pin 4 Rlo is 0 Volts and Pin 6 Rhi is 10 Volts, no leds will show with pin 5 at 0 Volts and all leds will show when pin 5 is at 10 Volts.

Bertus

 

[Maglatron]

Hello,

When pin 4 Rlo is 0 Volts and Pin 6 Rhi is 10 Volts, no leds will show with pin 5 at 0 Volts and all leds will show when pin 5 is at 10 Volts.

Bertus

so if pin 4 Rio is 0 Volts and pin 6 Rhi is 5 Volts, no leds will show with pin 5 at 0 Volts and all leds will show when pin 5 is at 5 Volts? is this good?

 

[bertus]

Hello,

Yes, That is correct. You can make the LM3914 show voltages between the Rlo voltage and Rhi voltage.

Bertus

 

[Maglatron]

fantastic so in the filter image of the tool that helps design filters, is that set correctly?

 

[Maglatron]

so my next question is, if I have a 12v battery and some LM7805's can you make positive-ground-negative with it, if you get my drift?

 

[Harald Kapp]

example?

Can you read a datasheet?

 

[Harald Kapp]

I have a 12v battery and some LM7805's can you make positive-ground-negative with it

No. Not reliably.

Use a voltage inverter, either a switched capacitortype or a scwitch mode inductor based one.
Note that regulating 5 V from a 12 V source will dissipate a lot of energy.
Why do you need -5 V anyway? YOui could use single supply operational amplifiers (rail-to-rail) and a single 12 V supply only.

 

[Maglatron]

ok nice one just trying to keep the power usage down

No. Not reliably.

Use a voltage inverter, either a switched capacitortype or a scwitch mode inductor based one.
Note that regulating 5 V from a 12 V source will dissipate a lot of energy.
Why do you need -5 V anyway? YOui could use single supply operational amplifiers (rail-to-rail) and a single 12 V supply only.

Can you read a datasheet?

Not very good at reading the datasheets yet, BUT I am getting better!

 

[Maglatron]

Reading the datasheet again now!

 

[Maglatron]

So there is a lot of information to take in, and I don't understand it all, I found this in the datasheet though!



do you just connect the pins 9 to ground for cascaded bar graph mode?

 

[Maglatron]

can you point me to any videos on voltage inverters of switched capacitor type or a switch mode inductor based one please.

 

[Maglatron]

Or even better, could you do a mock up of an asi file for LTspice, that would be exellent and so cool, so what I need is 12v to ground to -12v, for powering the op-amps, could you do that for me please???!!!

 

[Maglatron]

I see what you are saying now
#

Why do you need -5 V anyway? YOui could use single supply operational amplifiers (rail-to-rail) and a single 12 V supply only.

I've bought the TL074's now though

 

[Maglatron]

Can you recommend a rail to rail single supply op-amp quad in a dip package that would work for my application?

 

[Maglatron]

does the op-amp wizard tool work with the single supply operational amplifier?

Why do you need -5 V anyway? YOui could use single supply operational amplifiers (rail-to-rail) and a single 12 V supply only.

 

[Maglatron]

Also if i were to use a battery with a voltage inverter to get the desired positive and negative could I use these voltages across all of the operational amplifiers or would I need to make the voltage circuit for all of the operational amplifiers?

 

[bertus]

Hello,

The filter circuit can be changed to single supply, using a virtual ground reference:

Bertus

 

[Maglatron]

Ok what is a virtual ground reference point and can I use my TL074's