What do you need to add to this schematic

[rascupanamuha]

what do you need to add to this schematic to make it turns off only one led in the moment? and when you switch back, it shows as many leds as it should?
i have seen that somewhere...
https://www.electro-tech-online.com/attachments/vu-meter-with-gain-png.32468/

 

[ChrisP58]

Deleted incorrect information.

 

[dr pepper]

If you connect pin 9 to pin 3 you'll put the chip in bar mode.
That said there are different ways of getting bar mode, you can put the chip in dot mode and connect the led's in series.
You say that the chip turns one led off, are you saying all the leds light and the indicated led goes out?, sounds like maybe your using a common cathode display if thats the case, the chip is meant for a common anode, not a problem if your using individual leds, but is an issue if your using a module with a com cath.

 

[rascupanamuha]

Thank you all i have just solved the problem by adding the switch between pin 9 and +12V. Now i have bar and dot mode.
I have the other problem:
I have made my vu metar based on these schematics https://www.electro-tech-online.com/attachments/vu-meter-png.32467/

and i did switch between amplifier and no amplifier, and the problem is that without amp, everything works perfecly, and with it it turns on all the leds although there is no input signal?

 

[audioguru]

the problem is that without amp, everything works perfecly, and with it it turns on all the leds although there is no input signal?

I posted the wrong circuit at Aaron Cake's site. Then it was copied to here.
The LM3915 is supposed to be set up with a maximum input of 10V, not 1.25V as shown (pin 7 and pin 8).
With a maximum input of 1.25V then the small difference between the transistor forward voltage and the diode's forward voltage is too much. When the maximum input is set to 10V then the small difference does not matter.

 

[audioguru]

Grounding pin 9 of the LM3915 puts it into dot mode, where only one led is on at a time. Is that what you are looking for?

Refer to the manufacturers datasheet for the LM3915 for more info.

Please do not post WRONG things.

 

[ChrisP58]

Please do not post WRONG things.

Thanks for pointing out my mistake. I appreciate it.

 

[rascupanamuha]

Hmmm. So is there a way i could repair this? You said that this is for leds to show at full brightness, not just dimm.

 

[audioguru]

The transistor and diode circuit is a "peak detector" that is shown in the datasheet for the LM3915 except there the IC has two resistors at pin 8 that sets the reference voltage (full scale input voltage) to 10V so that the error caused by the transistor and diode does not turn on a few LEDs when the signal level is low.
The peak detector keeps the LEDs very bright for a moment. Without the peak detector then the LEDs turn on and off faster than your vision so they appear as a dim blur.
The datasheet has more complicated peak detector circuits that work very well and use an opamp and a dual-polarity supply.

In my "VU Meter" I made a peak detector with an MC33171 single-supply opamp and it works perfectly when the reference voltage is only 1.25V. It is here:

 

[rascupanamuha]

Thank you very much. It is more complicated than the other schematic so i will keep it that way. But i will make another one with this schematics u gave me, so thank you

 

[rascupanamuha]

I have one more question
I saw this: https://www.youtube.com/watch?v=r0M_ro1Cc2w&feature=related
My vu meter has dot mode, but not as clear as here. In my version, dot mod is pretty much like bar mode except that when top led is at full brightness, the last one down is not as bright. But in this video, u can see maybe 2-3 leds, and in mine almost all of them (not at the same time but in a few ms u cant see difference)

 

[audioguru]

In my version, dot mod is pretty much like bar mode except that when top led is at full brightness, the last one down is not as bright.

What is "the last one down"?
If the top LED is LED #10 then the NEXT one down is LED #9. If it has the peak detector circuit then all LEDs should have the same brightness. The circuit in the video seems to have a peak detector circuit.