Large LCD devices of 1 or more exhibit a large driving capacitance to the driver circuits. To solve this problem, the drive circuit shown (see the figure) introduces a buffer amplifier for each of the three common lines. Each amplifier can be programmed independently for a quiescent current of 10, 100, or 1000 jllA. In this application, the bias network applies a voltage that sets the three quiescent currents to 100 uA. The display driver and...
Shows 8 digital tube display driver circuit, driven by the two ICM7211A, BCD / = binary data signal is sent to the BO-B3 ICM7211A end, select the digital signal divided into two groups were sent sentenced Dl ~ D4 end.
Our programmable MP3 player has an interface to an LCD with a HD44780 controller. These are alphanumeric LCDs with one to 4 lines of text and 16 to 40 characters per line. However, these LCDs (and LCDs in general) exist in two varieties: those that require a positive LC-driving voltage and those that need a negative LC-driving voltage. The H0420 (the programmable MP3 player that I referred to earlier) only supports LCDs with a positive...
This is an evaluation use of a small graphics LCD module. Last summer, SG12232C graphic LCD module has been sold sold for 1500 Yens from Akizuki Denshi and I bought it. However I could not find good application for the LCD module and it was going to go to junk box :-) so that I tried to use the LCD module temporary. Only displaying any still image is not cool, first I tried to display an audio wave form in real-time like a digital...
Almost any 2x16 character LCD module with Hitachi HD44780 controller chip will work. The LCD pin numbers on the schematic are not valid for all LCD modules. Please check the actual signal names on your particular LCD module. The selected DFCW frequency offset will be added to the output frequency when the DFCW input is grounded. This input has a weak pull-up in the PIC.
A speedometer measures a wheel`s rotational speed. Unlike conventional mechanical and moving-magnet designs that use analog moving-pointer displays, the electronic speedometer in this Design Idea features a digital readout and a power-saving device that uses few components. Figure 1 shows the digital speedometer`s circuit design. An Atmel AVR AT90S2313 microcontroller, IC1, drives IC3, a 16-character, two-row LCD.
To program some AVR microcontroller unit (MCU) you will need an AVR programmer. The better way to do that, is to buy some development kit like STK-500. This kit have the advandage to give you serial port, LCD connector, SRAM socket, 8 switches, 8 LEDs, connectrors for all of the ports of MCU and more, to one board. I sugest to beginers, to start working with STK 500 or some else developmert system, it will help them very much.
Driving a bare LCD does not necessarily require specialized interface circuitry or peripherals. This Design Idea describes an alternative drive scheme, which you can easily implement using the general-purpose outputs of a microcontroller. Many embedded-system applications need to interact with a user by displaying simple numeric or alphanumeric characters. Seven- or 14-segment LED displays are readily available at low cost and in many sizes....
There is enough of poorly constructed RS232 alike TTL level interfaces (+5volt) , this one generates it`s own +/- 10..11volts as RS232 specs. require , and is able to use very long cables like RS232 can , and protects computer as well , nice in funny environment like inside a "MP3 in car" setup. There is plenty of ready RS232-Lcd controllers 4 sale , at least 3 types I know about... Common to them all is that they are slow or does not have...
This is a project that I started back late 2003 when I just starting to learn PIC programming. I wanted to building something that actually did somthing useful. This project is based on a PIC16F84. I actually came up with this idea and then after doing some searching I found that a few people had the same idea. But, I wanted to build my own that I could call mine, developed by me.
Integrating analog-to-digital converters (ADCs) provide high resolution analog-to-digital conversions, with good noise rejection. These ADCs are ideal for digitizing low bandwidth signals, and are used in applications such as digital multi-meters and panel meters. They often include LCD or LED drivers and can be used stand alone without a microcontroller host. The following article explains how integrating ADCs work. Discussions include...
This project displays telephone numbers decoded from tones. A microphone picks up the tones, a preamplifier boosts the signals, an SSI-202 DTMF chip decodes the tones, a Basic Stamp acts as an interface to an LCD display and also provides "RS-232" serial output. If you`d like to build your own tone decoder "from scratch", read on: You might have trouble finding the SSI-202 chip, even though Radio Shack used to sell them. In the United States,...
White LEDs are popular for portable equipment LCD backlights because they are less complex, less expensive, and smaller than CCFL backlights. Portable equipment like PDAs, cellphones, and digital cameras require backlights because they are converting to color LCD displays. This article discusses charge-pump and inductor step-up converter solutions for powering white LEDs in series or parallel configurations. Regulated-voltage or...
White LEDs are widely used in small LCD backlight
applications for simplicity, high reliability and low cost.
However, due to variations in the forward voltage drop of
white LEDs, matching the brightness becomes a major
design consideration for multiple LED applications. Since
LED brightness is proportional to current rather than
voltage, a constant-current source driving LEDs in series
should be used to ensure the same illumination of...
The circuit comprises simply the PWM source, capacitor C, and resistors RD and RW. For CMOS circuits, you calculate the open-circuit output voltage as VCONT=D½§VDD, where VCONT is the control circuit`s output voltage, D is the PWM duty cycle, and VDD is the logic-supply voltage. The control circuit`s output impedance is the sum of the resistor values RD and RW: RCONT=RD+RW. For the circuit of Figure 1, the output voltage, VOUT, is a...
Figure 1 shows a method for driving all the LEDs with a single driver IC from Catalyst Semiconductor (www.catsemi.com), the CAT32. Power comes from a single lithium-ion battery cell. A FET switch can independently turn off the group of six LEDs. The shutdown input, , on the CAT32 turns off all the LEDs. LED brightness is a direct function of the current running through the LED, and typical values are 10 to 20 mA for white LEDs. The CAT32...
Figure 1 shows a simple, cost-effective way of providing these bias voltages. A step-up regulator, IC1, forms the heart of the circuit. This regulator switches at a constant frequency of 1 MHz and a fixed duty cycle of 70%. IC1 steps up the input voltage to 5V by storing the energy in the inductor when the internal MOSFET, M1, is on and transferring this energy to C1 when M1 is off. IC1`s hysteretic gated-oscillator control scheme achieves the...
Flat-panel LCD monitors offer excellent image quality and more compact form factor than CRTshence, their steadily increasing popularity. Unfortunately, the complexity of their manufacturing process makes LCD monitors considerably more expensive than CRTs. The amplifier that drives VCOM, the voltage on the backplane of the LCD panel, must be able to drive large capacitive loads, deliver high peak output currents, and maintain a constant output...
This project is a self-contained serial terminal using a PIC16F84 microcontroller chip, an inexpensive LCD character display, a keypad, and very little else. It is full-duplex, meaning keypresses cause RS-232 output, and RS-232 input makes characters appear on the LCD. If you connect the RS-232 output to the input you can see the keys as you press them, without connecting to anything else (thats called looping back).
With the advent of HDTV and DVD video, there is a
renewed focus on RGB and color-difference component
video to maximize picture quality. LCD displays have also
entered the mainstream for high-end and portable computer
displays. These applications often require high
speed triple amplifiers for routing and conditioning video
signals. With these applications in mind, Linear Technology
has introduced the LT®1399 and LT1399HV triple
The circuit in Figure 1 saves I/O pins. It uses an 8051 µC, and only four I/O pins (P1.0 to P1.3) drive the LCD, instead of the 11 pins other displays require. Data transfers in a serial mode through the P1.0 port of the µC. The µC interfaces to Pin 2 of IC1, a 74HCT4094 8-bit shift register. Serial data advances on every clock pulse and transfers to the shift register. The register converts the serial data to parallel data, available on the...
Large LCD (liquid crystal display) displays designed to
replace CRTs (cathode ray tubes) in desktop computer
applications are becoming available. The LCDs reduced
size and power requirements allow much smaller product
size, a highly desirable feature.
The circuit in Figure 1 is an effective driver for LCDs. The circuit comprises two main sectionsthe ICM7211 drivers (IC2 and IC3) and the YN06 display itself (IC1). The Intersil (www.intersil.com) ICM7211 is a 4-bit LCD driver that needs no external components. It contains three basic sections: a reference signal-generator circuit, an input and display-channel section, and a digit-selection and drive circuit.
You can connect seven-segment LCDs using only a two-wire interface (Figure 1). The two-wire interface may be at the field-effect, direct-drive LCD or at a serial interface (such as I2C) that uses an eight-pin microcontroller. The design in Figure 1 uses an Atmel (www.atmel.com) ATtiny12 microcontroller, IC1. VCC can range from 2.7 to 5.5V.
A practical 92% efficient LCD backlight design is a classic
study of compromise in a transduced electronic system.
Every aspect of the design is interrelated, and the physical
embodiment is an integral part of the electrical circuit. The
choice and location of the lamp, wires, display housing
and other items has a major effect on electrical characteristics.
The circuit in Figure 1 is a dual, grounded-lamp backlight
inverter that operates from an input of 9V to 24V, delivers
current from 0mA to 9mA per CCFL and has a dimming
ratio greater than 100:1. The LT1768 in the circuit is a
350kHz fixed frequency, current mode, pulse width modulator
that provides the lamp-current control function.
The idea is simply to turn off the negative voltage load. Some examples:-
- Bias votlages for LCD panels
- RF Amplifiers
- Audio Amplifiers
The good thing about this design is that i can make use of the system i/o voltage to control the on/off and this is the whole idea. However, there are many many type of load switches that turn of negative voltages. Here is the suggestion,
Linear Technologys LT®3466 is a dual step-up converter
capable of driving up to 20 white LEDs with a programmable
constant current. The device is also capable of
driving asymmetric LED strings with independent dimming
and shutdown control for multipanel LCD backlight
The Car shows the distance a train travels on a 5 digit LCD display. The distance is indicated down to 1/100th of a mile (about the length of a 50 foot car) with an accuracy of approximately plus 2 percent using a standard 33 inch freight car wheel.
Simply stated, the Odometer Car counts the number of revolutions of one of the axles, divides it by six and displays the result on the counter module.