Hi to all !
I have one small problem with my vu meter built on my LM3915 IC chip.
I set current values for all all leds and the input signal but i'm confused with setting of gain
How can i make the IC to show at pin1 -18db or any other value that i want.
I want a scale from -18db to 9db in 3 db steps.
and another scale from --12db ---> +12db for other vu meter
Please help
I have one small problem with my vu meter built on my LM3915 IC chip.
I set current values for all all leds and the input signal but i'm confused with setting of gain
How can i make the IC to show at pin1 -18db or any other value that i want.
I want a scale from -18db to 9db in 3 db steps.
and another scale from --12db ---> +12db for other vu meter
Please help
Please check the datasheet first.
http://cache.national.com/ds/LM/LM3915.pdf
Secondly, the "gain" is set by the reference voltage, meaning the DC voltage for obtaining 0dB (all LED's on). You must also have a rectifier circuit with average or peak function. All this is in the datasheet.
http://cache.national.com/ds/LM/LM3915.pdf
Secondly, the "gain" is set by the reference voltage, meaning the DC voltage for obtaining 0dB (all LED's on). You must also have a rectifier circuit with average or peak function. All this is in the datasheet.
I don't understand what is the need of an rectifier circuit in a vu-meter. I read LM3915 datasheet but is too heavy to understand.
Please help
All i want to do is to make a vu-meter with a log scale :
-24, -21, -18, -15, -12, -9, -6, -3, 0, +3 dB
Difference between LM3915 & LM3916 ....
Please help
All i want to do is to make a vu-meter with a log scale :
-24, -21, -18, -15, -12, -9, -6, -3, 0, +3 dB
Difference between LM3915 & LM3916 ....
I think you have to read the datasheet, look at the pages at the end where you have very practical advices.
A rectifier with averaging or peak function will create a more "steady" light (looks nicer) but as I understand the LM391x can handle pure AC signals also.
You must adjust the reference voltage so it corresponds to the voltage or your +3dB, 1.4 volts maybe?
A rectifier with averaging or peak function will create a more "steady" light (looks nicer) but as I understand the LM391x can handle pure AC signals also.
You must adjust the reference voltage so it corresponds to the voltage or your +3dB, 1.4 volts maybe?
What about this circuit:
http://users.otenet.gr/~athsam/vu_meter_3.htm
What are the dB stages on each led ?
If I load a signal between 60mV - 1.25V all leds will be lit to 0dB ?
http://users.otenet.gr/~athsam/vu_meter_3.htm
What are the dB stages on each led ?
If I load a signal between 60mV - 1.25V all leds will be lit to 0dB ?
I'm afraid that you'll have to read the datasheet in order to get a working VU-meter. If you check the "Application hints" you'll find a couple of rectifier circuits, check especially page 11, figure 4.
http://www.national.com/ds/LM/LM3875.pdf
http://www.national.com/ds/LM/LM3875.pdf
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