4 digit LCD or LED display
in [Design]
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From: John Fields on 23 Feb 2006 17:32 On Thu, 23 Feb 2006 20:32:06 GMT, 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 --- No, On Wed, 22 Feb 2006 07:19:14 -0600, John Fields <jfields(a)austininstruments.com> wrote: >Drive the displays with 8 times the current. -- John Fields Professional Circuit Designer
From: Rich Grise on 23 Feb 2006 20:01 On Thu, 23 Feb 2006 13:07:36 -0800, William at MyBlueRoom wrote: > The TI chip is not cheap but its part number is TIL311 > > http://www.taosinc.com/images/product/document/til311-e4.PDF Hey, thanks for this! Man, it brings back memories. <reminiscence> I had just got out of the USAF, and nailed a job: "Engineering Tech" at some high-buck outfit that some guy accidentally started because he discovered something in school and when he started having apparatuses built, other people came to him to ask him to build them some more of those apparatuses. "So, not knowing anything about going into business, I went into business. <heh, heh, heh>", he said, at the new-hire orientation. And it had turned into this multi-million-dollar company. Anyway, another tech and I got hired at the same time, and he was from Holland, albeit he spoke American English better than at least 50% of the people I've met. ;-) He was an awesome tech, too, like, if I needed a tech, and he and I both applied for the job, I'd hire him, he was that good! ;-) Anyway, to get to the point, when the TIL311 got announced, and we actually had an opportunity to design them into a test fixture or whatever, he sort of announced it to the lab: "Tee eye ell three, eleven." He almost sang it. They were like $13.00 a pop, in 1976. =:-O </reminiscence> Thanks again for reminding me of the number - it's kinda like popping a mental zit. ;-) Cheers! Rich
From: Rich Grise on 23 Feb 2006 20:10 On Thu, 23 Feb 2006 16:32:10 -0600, John Fields wrote: > On Thu, 23 Feb 2006 20:32:06 GMT, Rich Grise <richgrise(a)example.net> >>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. :-) > > No, > >>Drive the displays with 8 times the current. Yeah, 8 times _what_ current? He mentions 560 mA. It wouldn't take many ohms to knock that down to 500, and voila: <quote> Ideally suited for interfacing between low-level logic circuitry and multiple peripheral power loads, the Series ULN20xxA/L high-voltage, high-current Darlington arrays feature continuous load current ratings to 500 mA for each of the seven drivers. At an appropriate duty cycle depending on ambient temperature and number of drivers turned ON simultaneously, typical power loads totaling over 230 W (350 mA x 7, 95 V) can be controlled. Typical loads include relays, solenoids, stepping motors, magnetic print hammers, multiplexed LED and incandescent displays, and heaters. All devices feature open-collector outputs with integral clamp diodes. </quote> from: http://www.ortodoxism.ro/datasheets/allegromicrosystems/2001.pdf So, what's the problem? The reason I suggested it is it's easier to stuff a DIP than 7 individual transistors and schtuff. OK? :-) Thanks, Rich
From: Rich Grise on 23 Feb 2006 22:02 On Fri, 24 Feb 2006 02:42:15 +0000, Michael A. Terrell wrote: > John Fields wrote: >> >> >So, what's the problem? The reason I suggested it is it's easier to stuff >> >a DIP than 7 individual transistors and schtuff. OK? :-) >> >> No, it's not OK. > > Maybe its time to some new sci.electronics newsgroups: > > news:sci.electronics.blowhards etc. Yawn.
From: John Fields on 23 Feb 2006 22:50
On Fri, 24 Feb 2006 03:01:35 GMT, Rich Grise <richgrise(a)example.net> wrote: >Geez! Read me the riot act, why don't you? --- Stop trying to play the victim. --- >I thought the guy was trying to avoid 7 more transistors, and figure >out how to scan a bunch of segments, so he needed a lot of current. --- The point was that in order to mux the 8 digit display and have it exhibit the same apparent brightness as if it were being displayed statically, he'd have to pump eight times more current into the segments for 1/8 of the time. As I recall, the OP understood that and responded with what would be required of the segment drivers, as well as what would be required of the column/digit drivers. I don't believe you've addresed the latter issue. --- >Excuse me for trying to be helpful. --- Trying to be helpful and _actually_ being helpful are often mutually exclusive, especially when one thinks one knows more than one do. --- >Or don't, as is your wont. --- Wanting to be helpful and _actually_ being helpful are often mutually exclusive, especially when one thinks one knows more than one do. -- John Fields Professional Circuit Designer |