4 digit LCD or LED display
in [Design]
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From: Russ_Verdon on 21 Feb 2006 06:30 ; <wrongaddress(a)att.net> wrote in message news:1140488077.255939.203750(a)g44g2000cwa.googlegroups.com... > I'm looking for a 4 digit LCD or LED display to use with a PIC > processor. Something easy to use that will latch 4 bit data from the > processor to each of 4 (7 segment) digits. > > Anybody know of a part number and supplier? > > -Bill > Hi I just built a tachometer using 74LS367 latches to save me multiplexing 4 LEDS See the snippet from my code below. It worked fine. Russell PIC 16F628 Assembly Programme ;*************** TACHOMETER ************************* ; ;Code by R Verdon 28/1212/2005-17/1/2006 VERSION 9.2 ;Final 17/1/2006 ; ;HARDWARE ; 4 x 7 segment common Anode displays used. Cathodes to +5V via 150 ohm ; 1 x 74ls373 octal latch used for each 7 seg LED ; Port A drives a latch for each Led's Cathodes ; Port B presents data to the latch for the cathode segments ; To latch data, put 7 seg data on PB1-7 and clock port A bit for the digit, ; latched on falling edge of the pulse at pin 11 of the selected 74LS367. ; ;PA0 Anode for MSD ----| ;PA1 | ______ ;PA2 | | | ;PA3 Anode for LSD | _a | ;PA4,5 NO CONNECTION | f/g_/b | ; | 74LS367 1(GND) e/__/c | ; | d | ; | ______________|__ | ;INT ON PB0 | | _____ OE| | | ;PB1 a LED SEGMENT -| | --PA0 11|---- |E | | | | ;PB2 b | | | | | | | ;PB3 c |__________2|---- |D Q|---------|>-| seg a LSD LED--------| ;PB4 d | |____| | ;PB5 e | | ;PB6 f | 7 more of these | seg b, c,d etc ;PB7 g LED SEGMENT; per 74ls373
From: William at MyBlueRoom on 21 Feb 2006 10:58 Your design seems to save no I/O, 4 digit select lines plus 7 segment lines plus you have to be careful not to draw too much current for the anodes from the PIC the CD4511 would only require 8 lines (4 data , 4 latch) and be the same chip count plus you get the decoder. http://www.fairchildsemi.com/ds/CD/CD4511BC.pdf Muxing a display is easy in a pic, 50hz or better will appear flicker free to most and is easy to do in software on a 16F628 (interrupt driven) you can also reduce pin counts see my Daisy schematic to see what Charlieplexing looks like www.digitalglu.com Bill
From: linnix on 21 Feb 2006 11:47 wrongaddress(a)att.net wrote: > I'm looking for a 4 digit LCD or LED display to use with a PIC > processor. Something easy to use that will latch 4 bit data from the > processor to each of 4 (7 segment) digits. > > Anybody know of a part number and supplier? Is AVR ok? We are using an Atmega169 (with 25 segments LCD drivers) for an LED panel. The chip is designed for LCD, but we are using N-channel MOSFETs (2N7002) to boost the power. You can load data from serial or spi.
From: slebetman@yahoo.com on 21 Feb 2006 21:56 William at MyBlueRoom wrote: > Your design seems to save no I/O, 4 digit select lines plus 7 segment > lines plus you have to be careful not to draw too much current for the > anodes from the PIC > > the CD4511 would only require 8 lines (4 data , 4 latch) and be the > same chip count plus you get the decoder. > > http://www.fairchildsemi.com/ds/CD/CD4511BC.pdf > > Muxing a display is easy in a pic, 50hz or better will appear flicker > free to most and is easy to do in software on a 16F628 (interrupt > driven) you can also reduce pin counts see my Daisy schematic to see > what Charlieplexing looks like > > www.digitalglu.com > > Bill A simple shift register is even better (as I stated elsewhere in the thread). A 74HC595/74LS595 requires only 3 lines and be the same chip count and is a very easy to find common part. A 74HC164/74LS164 saves even more pins, using up only 2 lines. Around 12 PIC instructions are enough to replace a hardware decoder so in my opinion they are not worth it (besides, they are rarely able to display hexadecimal). What's more, once you get the hang of shift registers you can use use the 74HC165/74LS165 to expand the number of input lines.
From: wrongaddress on 21 Feb 2006 23:42
> You could use a CD4511 BCD to 7 segment latch decoder driver, you would > need 4 of them and at least 6 I/O lines (assuming external demux) or > the TIL311 display with latch $$ Yes, but I have to drive 8 digits and don't want to add 8 chips. I thought there might be a 7 segment LED digit with the latch/decoder built in, or a group of 4 with the same. That would make it easy. I can't do it with multiplexing since the duty cycle would be 8 to 1 and the display wouldn't be very bright. -Bill |