4 digit LCD or LED display
in [Design]
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From: wrongaddress on 22 Feb 2006 17:02 > Drive the displays with 8 times the current. ---- Yes, that's a possibility. It would require 7 more transistors and resistors to drive the segment lines since the PIC won't drive more than 25mA. Probably need a minimum of 80mA. And with 7 segments on, the transistor controlling the common line would be running at 560mA. So, I need 8 medium power transistors rated around 1 amp. -Bill
From: Rich Grise on 23 Feb 2006 15:30 On Tue, 21 Feb 2006 20:42:58 -0800, wrongaddress wrote: >> 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 I was looking for that old TI chip, whose number I can't remember, which had a BCD to 7-segment decoder and the LED display on the same chip. Well, in the same package. ;-) I didn't find it yet, but I did stumble on this: http://www.jcelectronica.com/articles/CPLD%20application.htm He uses a CPLD, and apparently CPLD outputs can drive LEDs. :-) Good Luck! Rich
From: Rich Grise on 23 Feb 2006 15:32 On Wed, 22 Feb 2006 14:02:26 -0800, wrongaddress wrote: >> Drive the displays with 8 times the current. > > ---- > Yes, that's a possibility. It would require 7 more transistors and > resistors to drive the segment lines since the PIC won't drive more than > 25mA. Probably need a minimum of 80mA. And with 7 segments on, the > transistor controlling the common line would be running at 560mA. So, I > need 8 medium power transistors rated around 1 amp. > ULN2003. :-) Good Luck! Rich
From: William at MyBlueRoom on 23 Feb 2006 16:07 The TI chip is not cheap but its part number is TIL311 http://www.taosinc.com/images/product/document/til311-e4.PDF as for power consumption that why you mux a display or at least use HE RED displays like MAN6940 Bill www.myblueroom.com
From: martin griffith on 23 Feb 2006 16:21
On Thu, 23 Feb 2006 20:32:06 GMT, in sci.electronics.design Rich Grise <richgrise(a)example.net> wrote: >On Wed, 22 Feb 2006 14:02:26 -0800, wrongaddress wrote: > >>> Drive the displays with 8 times the current. >> >> ---- >> Yes, that's a possibility. It would require 7 more transistors and >> resistors to drive the segment lines since the PIC won't drive more than >> 25mA. Probably need a minimum of 80mA. And with 7 segments on, the >> transistor controlling the common line would be running at 560mA. So, I >> need 8 medium power transistors rated around 1 amp. >> > >ULN2003. :-) > >Good Luck! >Rich > The TPIC6B595 is a monolithic, high-voltage, medium-current power 8-bit shift register designed for use in systems that require relatively high load power. from TI martin |