**broken link removed**
Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
Page 9 shows pin 9 of the first LM3915 connected to pin 1 of the second LM3915 and the 11th LED. It explains that when the 11th LED lights then pin 9 drops 1.5V or more which turns off the 10th LED.ya i tried this circuit but the tenth led does not light brightly and does not completely gets off when the 11th led is turned on.
Page 9 does not have an opamp. The opamp is shown in figure 6 on page 12.It didnt worked like with the opamp showed in page 9, i used single polarity opamp is that the problem?
Page 9 shows pin 9 of the first LM3915 connected to pin 1 of the second LM3915 and the 11th LED. It explains that when the 11th LED lights then pin 9 drops 1.5V or more which turns off the 10th LED.
Your circuit will work wrong if a very important supply bypass capacitor close to the ICs is missing. The supply bypass capacitor C1 is shown on the first schematic in the datasheet.
Page 9 does not have an opamp. The opamp is shown in figure 6 on page 12.
When the input signal swings negative then a single-supply opamp might have its input damaged unless it has a dual-polarity supply.
Which opamp did you use?
i am using 12 v supply, and now where should i use 13 k resistor?so the power supply to the LM3915 ICs, peak detector opamp and opamp for the LM3915 must be 12V or 13V. Or a lower supply voltage can be used if the full-scale voltage is reduced by reducing the value of the 13k resistor.
I shunted the 11 th led with 10 k resistor , i worked but now due to dat 10th led glows vry dimOn page 9 the datasheet says that the first LED of the second LM3915 (the 11th LED) might glow faintly when it should not be lighted. It says to connect a 10k resistor parallel to the 11th LED so that it does not light when it shouldn't.
The 13k resistor sets the reference voltage for the two LM3915 ICs.i am using 12 v supply, and now where should i use 13 k resistor?
You might not see a difference.What will happen if i wil use full wave precision peak detector rather than half wave like yours?
Maybe the LM3915 ICs are fakes, not made by National Semiconductor.I shunted the 11 th led with 10 k resistor , i worked but now due to dat 10th led glows vry dim
Breadboards have intermittent contacts. They have too much inductance and capacitance for RF circuits. Their millions of long wires pickup interference.i am using breadboard, do they create problem????
It is shown on figure 6 of the datasheet connected from the Reference Adjust pins #8 to ground.13k is for reference voltage but on which pins shoud i connect it
My guess would be that you need to do some averaging prior to the LM3915.
**broken link removed**
https://www.electro-tech-online.com/custompdfs/2012/09/Avrg1980.pdf
Two things I can think of.now the problem is i want smother transitions, as in dot mode i want only one led to on at an instant of time,, but now there are atleast2-3 on sometimes four...how can i solve this problem
My LM3915 Sound Level Indicator project has a peak detector and in the DOT mode it shows ONE lighted LED bouncing around.
The datasheet says that oscillation or excessive noise causes a few LEDs to light in the DOT mode (from using a breadboard?).
Hint, hint: don't use a breadboard.
I made my project on a stripboard with all strips cut to be fairly short so they do not pickup interference. Its enclosure is plastic, not metal.
My circuit has extra gain and an AGC circuit so that it has a lot of gain when the levels are low then it reduces the gain when the levels are high. It shows a pin dropped on the floor in the next room and also shows very loud sounds.
Two things I can think of.
1) bread board problems causing oscillations. You may have a opamp or LM3915 oscillating. OR Ground noise. Power power supply noise.
2) the capacitor in the peak detector needs to be larger. That will hold the value longer. Try a much larger cap and see if it helps.
Good grief or bad grief! TOO MANY simple questions. Please LEARN the basics of electronics.
My Sound Level Indicator project is designed to be powered from a little "9V" rechargeable Ni-MH battery or its little 9V charger.
Some of its resistors and the LM3915 IC will burn if a 12V supply is used. Redesign the circuit so a 12V supply can be used.
1) The low dropout 5V regulator allows the preamp and oscillator to have a regulated 5V voltage. With your higher supply you can use an ordinary 7805 5V regulator.
2) R16 shares the heating when the supply is 9V, when there are two red LEDs in series at each output and when the current is set at about 26mA. Recalculate the value of R16 and its amount of heating when your power supply voltage is much higher.
The low dropout regulator needs C6 and C7.
3) The preamp and oscillator are designed for a +5V regulated supply. Redesign the circuit for a different voltage if you want.
4) The mic input is too sensitive for a line level input. An attenuator (made with a few resistors) is needed to reduce the sensitivity so a line level input can be used. Also the resistor R1 that powers an electret mic must be removed.
5) The datasheet for the LM3915 says that the first LED might light dimmly when it is supposed to be off because it is fed a small current so it can be the 11th LED when two or more chips are cascaded. The datasheet says to use a 10k resistor parallel to the SINGLE LED. I used 22k for R18 since my circuitry has TWO red LEDs in series.
6) The datasheet has a graph of output current which is determined by multiplication of the current fron pin 7 to ground. Each output in my circuit has a current of 26mA when switched to Bright and is 5mA when switched to Dim.
7) If you use transistors at the outputs for multiplexing then R16 and C7 might not be needed. C6 is needed when the circuit is powered from a battery or a very cheap DC power supply.
i was tryn to run more leds by using transistor, but m facing a problem...led is not turning completely off.....there is still some current flowing through it when there is no output from 3915
here is the circuit i am usingView attachment 67225