Sallen Key Low Pass Filter, bandpass filter

[Maglatron]

I did a quick sum and if all the LED's were lit at once it would draw 6.4 amps! I want to use a lithium ion battery 12v along with 7809 regulators, can I do this if I use more that one regulator, each one supports 1.5 amps so if I used 5 of them, what do you recon?

 

[Maglatron]

??

 

[kellys_eye]

I did a quick sum and if all the LED's were lit at once it would draw 6.4 amps!

Which will never happen..... your device is a peak meter (emphasis on the peak) and will only require a properly designed power supply that can cope with said peaks. As for using 7809 regulators - you only need them for the audio processing side. You could use 'any' supply voltage to drive the LEDs (via buffers).

 

[Maglatron]

yes it would never happen but could I do like this:

 

[Maglatron]

they are LM7809's

 

[Maglatron]

Ok yes only need audio processing side because can control the LED brightness with the resistor on pin 7 of the LM3914's gottcha!

 

[bertus]

Hello,

The led current can be adjusted between 2 and 30 mA.
Have a look at these schematics.
For the LM3914:

For the LM3915:

In both schematics there are formulas for setting the led current.

Bertus

 

[Maglatron]

Ok cool, I'm going to have to read that a couple times. I'll get it at some point! and thanks

 

[Maglatron]

Ok got it! if I want to have 3milliamps divide 12.5/0.003 = resistor of 4166ohm resistor on the pin 7 to ground

 

[bertus]

Hello,

The current reference is between pin 7 and 8 of the chips.
It can be that pin 8 is grounded, but can also have a resistor to ground.

Bertus

 

[Maglatron]

ok what would you do for 3 milliamps?

 

[bertus]

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

 

[Maglatron]

to me this says 12.5/(desired) I-led = R1 no? and ground pin 8!

 

[bertus]

Hello,

R1 only sets the ledcurrent.
R2 lifts the adj connection to raise the reference voltage:

Bertus

 

[Maglatron]

To be honest I don't understand ref adj
does reference adjacent control the sensitivity of the voltage in, to turn on the LED's say it needs 12v in to get full brightness does it change it so all the LED's can be turned on with say 5v

 

[Maglatron]

I'm knocking off for the night, night

 

[Maglatron]

got my TL074's today, waiting on LM3914's got the bar graph LED's

 

[Maglatron]

so I need to know how much power to put into the op-amps (positive and negative voltage) to be sufficient on the output to drive the LM3914's?

 

[bertus]

Hello,

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.

Bertus

 

[Maglatron]

example?