By connecting pin 8 to ground the output at pin 7 will be 1. If two or more ICs are cascaded to drive 20 or more LEDs in the dot mode, pin 9 must except in the case of the final IC in the chain be wired to pin 1 of the following IC, and a 20k resistor must be wired between pin 11 and the LED-powering positive supply rail. You can insert the LM, turn the board over and solder one line of legs. In the LM, the resistors are logarithmically weighted, and thus produce a log display that spans dB to 0dB in 10 -3dB steps. In Figure 3 , the reference is shown externally connected to the internal potential divider pins 4 and 6. These will interface more or less directly in place of the 2N transistors in your circuit.

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Home Questions Tags Users Unanswered. When I opened it up I saw a board like this: This establishes power to the chip. Graphh example, I want a song with a loud base to make the bar graph shoot up to the top.

LED ‘Graph’ Circuits | Nuts & Volts Magazine

The IC responds only to the positive halves of such input signals, and the number of illuminated LEDs is thus proportional to the instantaneous peak value of the input signal.

LP, low voltage16 LEDs. With varying voltage, we get varying LEDs lit. On future posts, please be sure to include links to any datasheets you’re referencing, as well lmm3914 any schematics or pictures of what you’re trying to accomplish.


Since we are using LEDs with such long leads, we simply connect pin 4 to ground. The internal voltage reference of the IC produces a nominal output of 1.

LED ‘Graph’ Circuits

By adjusting VR1 appropriately we get 1. Solder the trimmer pots The two trimmer pots can be soldered.

At 5V, all 10 LEDs turn on. If 1 or no LEDs are lit, it can mean the battery is dead. The LM family are popular and versatile ICs that can each directly drive up to 10 LEDs but can easily be cascaded to drive larger numbers of LEDs and can drive them in either bar or dot mode.

Insert the LED array first and solder it from the opposite side.

Tag: Bar Graph Volt Meter Range 0 to 10v using LM3914

This would reduce the heat stress on the chip, or alternatively let you swap in ggaph colour LEDs as required. Figure 5 shows the connections for making a variable-range 1. I bought some of these LM boards from eBay: Nick Gammon 3 The basic Ln3914 17 to 19 LM and LM circuits are shown being driven directly from AC signal inputs, and this technique is adequate in many applications.

Note that pins 8 and 4 are shown grounded so, in this case, the bottom of the divider is at zero volts and the top pm3914 at 1. The meter gives audio power indication over the range mW to W. Turn clockwise if it is too low eg. Alternatively, you could also use the socket for the LED instead. Thus, if RV2 is set to apply 0.


With the component values shown, this circuit has a full-scale sensitivity of 10V and provides a LED-drive current of 16mA. In this case, R2-RV2 are effectively set to give a basic range of 2. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

Again no current-limiting resistors are necessary because the resistor R1 acts as the current-limiting resistor. In this case, all the LEDs will be off. You have the choice: You can do fancier things with this IC such as chaining multiple units together or selecting a range of voltages that the input signal should be between but that requires actually reading the datasheet and putting a voltage divider between the pin ref out and pin ref adj.

The doesn’t care if you play such tricks on it. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. It also supplies the current to the LEDs. As the resistance increases, the voltage increases, so the LEDs begin turning on.

Last modified: October 18, 2020