LM3914 | Electronic Project Circuits

Posts Tagged ‘LM3914’

Led light based music circuit with LM3914

This is a simple light running circuit by music This circuit is not difficult, is MONO, with a few accessories. Can be connected to the output of a CD or cassette player Time.
Operation of the circuit. Begins to be input via VR. The VR will function fine, signal strength coming. D1 will take disconnected hemisphere plus leaving only the signal hemisphere removed to activation of Q1. Signal is extended through Q1 to pin 5 input of IC1. By C1 forward delay of the IC is not the LED (connected to the output. of IC1) off immediately. The IC IC1 is finished. The act shows the effect of the voltage at IC1 pin 5 of the display by the LED to pins 1-19 of the IC, which is within range. compared to a multiple voltage standard circuits. The circuit can operate effectively. In the R1 that it will determine the current flowing through the LED. To prevent LED damage.
Use should be connected to the input of the circuit. To the speaker terminals, change the value of R3 is 10k and IC1 can choose to display two types Bar (Bar) when the pin 9 and a power source. Dots (Dot) on 9-pin to float to drop.

1 comment - What do you think? Posted by admin - November 25, 2010 at 7:41 am

Categories: LED Flasher, Meter Tags: led running display, light music, LM3914

Injector Pulse Width Monitor with LM324 ,LM3914

The schematic for the pulse width monitor. The heart of the circuit is the transistor current source which charges cap C10 to form an integrator. The theory is that the cap is charged and the voltage across it increases linearly for the amount of time that the injector is energized. As the injector is switched off the voltage in C10 is stored in cap C9 and then C10 is reset to 0 volts to get ready for the next cycle. The output of the circuit is the voltage across cap C9, this voltage is fed directly into U3 the bar graph chip to be displayed as a value between 1-10 on the LEDs. Potentiometer R31 sets the charge rate on C10 and basically sets the max injector on time that can be displayed.

The calibration on this circuit is pretty tricky. You’ll need an oscilloscope and a waveform generator. Setup a 62Hz 0-12v 50% duty cycle square wave at the input to the circuit. Use the scope to monitor the voltage across C10 Adjust pot R31 such that the ramping voltage across C10 just reaches the peak (starts to flatten out). Now adjust the pot R22 in the display circuit such that LED 10 just comes on.

With the calibration described above LED 1 corresponds to about 1.5ms and LED 10 corresponds to about 8ms of injector pulse width (on time). Injector duty cycle in dependent on engine speed according to the following relationship:
% duty cycle = ( pulse width / period )*100
period = 1/[engine speed (rpm) / 60]

Source: http://www.ggimages.com/rx7/pwm.html

Be the first to comment - What do you think? Posted by admin - September 19, 2007 at 10:37 pm

Categories: Automotive, Meter Tags: electronic motocycle ignition, LM324 detector circuit, LM3914, Pulse width monitor

LM3914 – Dot/Bar Display Driver

Features
Drives LEDs, LCDs or vacuum fluorescents
Bar or dot display mode externally selectable by user
Expandable to displays of 100 steps
Internal voltage reference from 1.2V to 12V
Operates with single supply of less than 3V
Inputs operate down to ground
Output current programmable from 2 mA to 30 mA
No multiplex switching or interaction between outputs
Input withstands ï¿½35V without damage or false outputs
LED driver outputs are current regulated, open-collectors
Outputs can interface with TTL or CMOS logic
The internal 10-step divider is floating and can be referenced to a wide range of voltages
General Description

The LM3914 is a monolithic integrated circuit that senses analog voltage levels and drives 10 LEDs, providing a linear analog display