This circuit can be a building block to build a number of other circuits. You have the choice: At 4V, 8 LEDs turn on. Using 10mA, resistor R1 calculates out to be 1. For example, if we’re measuring battery power in a circuit, the LED bar graph can project the strength of the battery life.

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The circuit is shown connected for bar-mode operation, using separate supply voltages for the LED display and for the actual IC, idsplay with the component values shown, gives a current drive of 10mA to each active LED.

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 displya of the following IC, and a 20k resistor must be wired between pin 11 and the LED-powering positive supply rail.

Use the pull up resistors near LM outputs, link into the inverters and connect the outputs of the inverters to ULN In the latter case, the low end of the IC2 graaph divider is coupled to the 1. As we turn the potentiometer so that its resistance, and, therefore, voltage increases, the number of LEDs that light up on the bar graph eisplay proportionally.

In Figure 3the reference is shown externally connected to the internal potential divider pins 4 and 6.

LM3914N – LM3914 Bar-Graph Display Driver

Figure 15 shows the connections for making a LED bar-mode voltmeter. It’s not a big deal. Assume that the IC logic is set for bar-mode operation, and that the 1. 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.


Many suitable circuits are published in op-amp application llm3914 and circuit reference books and encyclopedias, etc. We place a toggle switch on this pin so that we can switch between the 2.

According to the datasheet, if you are not using LEDs with leads that are 6″ or longer, you can connect this pin directly to ground. Again no current-limiting resistors are necessary because the resistor R1 acts as the current-limiting resistor. And then we can calculate resistor R1. This varies the voltage that is fed into the LM We connect one end terminal to 5V and the other end terminal to ground, while connecting the wiper terminal to pin diisplay.

The Darlington driver seven open collector darlington pairs with common emitters. If the switch is flipped to ground, the chip is in dot mode. The IC contains 10 voltage comparators, each with its non-inverting terminal taken to a specific tap on a floating precision multi-stage potential divider and with all inverting terminals wired in parallel and accessible via input pin 5 and a built-in unity gain buffer amplifier. The same voltage that powers the chip can be used for V LED We do not have to connect current-limiting resistors to the LEDs because the R1 resistor functions as the current-limiting resistor.

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How to Build an LM Dot/Bar Display Driver Circuit

The internal stage potential divider of dlsplay IC is floating, with both ends externally available for maximum versatility, and can be powered from either the internal reference or from an external source or sources. Next in pins 6,7, 8, we place our biasing resistors R1 and R2 to obtain the current of 10mA. Sign up using Email and Password.


These are the pins where the LED bar graph connects to. When the input voltage reaches the displsy. Basically, it can simulate bar graph results.

LED ‘Graph’ Circuits | Nuts & Volts Magazine

An LED displa graph is a device that can be a visual indicator of voltage output. The input pin 5 to the IC is fully protected against overload voltages up to plus or minus 35V.

In this circuit, the alarm unit may take the form of a piezo siren unit that generates an acoustic alarm sound, or a gated astable switch unit that repeatedly switches the LED brightness between high and low levels under the over-range condition, or may be a combination of both of these units.

With the component values shown, this circuit has a full-scale sensitivity of 10V and provides a LED-drive current of 16mA.

Practical graph circuits may be designed to generate either a bar-graph or a dot-graph display.

The output of each comparator is externally available, and can sink up to 30mA; the sink currents are internally limited, and can be externally pre-set via a single resistor R1.

We do and show the math below so that there’s a exact relationship between the voltage km3914 the LEDs lit on the bar graph.