My premise is to connect the output pins of the LM directly to the ULN see crude illustration Is this going to be possible? You can replace the potentiometer so with any type of sensor measurement to measure anything. But the first two of these families have now ceased production, and only the LM family remains. Pin 9 is left open-circuit to give dot-mode operation, and R1 has a value of R to give an LED current of about 30mA, thus giving a clear indication of brief instantaneous voltage levels. Thus, the LM is a linearly-scaled unit, specifically intended for use in LED voltmeter applications in which the number of illuminated LEDs gives a direct indication of the value of an input voltage or of some parameter that is represented by a proportional voltage.

Uploader: Gumi
Date Added: 11 May 2017
File Size: 60.62 Mb
Operating Systems: Windows NT/2000/XP/2003/2003/7/8/10 MacOS 10/X
Downloads: 93607
Price: Free* [*Free Regsitration Required]

An LED bar 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.

The LM is an pin chip. It’s not a big deal. 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.

Learning Electronics Need to brush up on your electronics principles? Next in pins 6,7, 8, bxr place our biasing resistors R1 and R2 to obtain the current of 10mA. I guess the LM must have all outputs low when it starts?

LM3914N – LM3914 Bar-Graph Display Driver

LED bar graphs are used often in VU meter circuits, in which the LED bar graph can be lit up visplay proportion to the amount of voltage a device is outputting. Dsiplay pinout of the LM is shown below. Figure 1 illustrates the bar-graph principle, and shows a line of 10 LEDs used to represent a linear-scale V meter that is indicating a 7V or b 4V; the input voltage value is indicated by the total number of LEDs that are illuminated.


ULN is pulled low through Q2. To calibrate the above circuit, first set the supply to 15 volts and adjust RV1 so that LED 10 just turns on.

For example, if we replace the potentiometer with a resistor and photoresistor in series, we can build a light-sensing device and then the LED bar graph and light to show the light intensity that the photoresistor dlsplay detecting. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

How these resistors are determined are given by the formulas given by the manufacturer. Vehicle tacho conversion circuit for use with a LED voltmeter. At 5V, all 10 LEDs turn on. This basic VU-meter circuit gives a bar-type display, with a dot-type current drain. If, for example, RV1 djsplay set to 2k4, pin 8 will be at 2.

All three devices of the LM family use the same basic internal circuitry, and Figure 3 shows the specific internal circuit of the linear-scaled LM, together with the connections for making it act as a simple LED Pin 5 is a very important pin.

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 Lm914 positive supply rail. For substantially lower full-scale RPM values, the C2 value may have to be increased — the value may have to be reduced on vehicles with six or more cylinders.


In the LM, all resistors in the chain have equal values, and thus produce a linear dislpay of 10 equal steps. Assume that the Displat logic is set for bar-mode operation, and that grapj 1. In Figure 16the C2 value of 22n is the optimum value for a full-scale range of 10, RPM on a four-cylinder four-stroke engine.

For many years, the best known ICs of this type were the U etc. The will pull low but the wants a high signal to turn on the output. The IC operates as follows. Figure 6 shows how to make a fixed-range V meter, using an external 10V zener connected to the top of the internal divider to provide a reference voltage. At 4V, 8 LEDs turn on. Since the reference voltage is 5V and there are 10 LEDs, each 0.

LMN – LM Bar-Graph Display Driver

This is the signal pin. Visplay no current-limiting resistors are necessary because the resistor R1 acts as the current-limiting resistor. In the LM, the resistors are logarithmically weighted, and thus produce a log display that spans dB to 0dB in 10 -3dB steps.

An over-range alarm-driver circuit, for use with bar-type displays.