4 digit LCD or LED display

Hey, thanks for this! Man, it brings back memories.

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. ", 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

Thanks again for reminding me of the number - it's kinda like popping a mental zit. ;-)

Cheers! Rich

Yeah, 8 times _what_ current? He mentions 560 mA. It wouldn't take many ohms to knock that down to 500, and voila:

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,

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

--- No, it's not OK.

The problem is that you don't know what you're talking about, but you try to assume an affable style which would cause the ignorant to believe that they should "believe" in you, nice inoffensive guy that you are. The second coming of Christ? No. A march of idiots headed for the sea? Hopefully...

In truth, your technical abilities generally stink, and you seem to want to do little more than to try to amuse us all with what you consider to be the wit of your various personnae.

That's fine if that's what's gets you off but, if you want to get serious, I suggest you knock off the crap and read the title of the newsgroup: sci.electronics.design.

-- John Fields Professional Circuit Designer

Maybe its time to some new sci.electronics newsgroups:

news:sci.electronics.blowhards news:sci.electronics.lusers news:sci.electronics.morons news:sci.electronics.totally.clueless and news:sci.electronics.wankers

for people like Rich, Phil, and a few others who think their s*it doesn't stink. Of course, in some cases its damn difficult to tell where they actually stop, and their s*it begins.

Geez! Read me the riot act, why don't you?

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.

Excuse me for trying to be helpful.

Or don't, as is your wont.

Thanks, Rich

etc.

Yawn.

Bill, What is so complicated about driving an 8-digit LED display? (BTW, you only wanted 4 digits originally :) ).

Some of the replies you have been getting are basically impractical (insufficient drive etc) so you are left with either muxing the display or using dedicated led driver chips. You didn't say whether this is for indoor or outdoor use etc but I'm guessing that it needs to be bright.

I have used the SAA1064 4-digit LED driver chip before and since it is I2C is very easy to bit-bash using just 2 I/O from any cpu you care to name. Two of these suckers would have you home and hosed in no time. Too simple really.

OK, but they might be a bit hard to get hold of. You can also try the serial drivers from Maxim etc etc

The mux'd approach is very easy to implement but of course you need either high-brightness displays or high-current drivers. You figure which way you want to go. Your software needs to run a low-priority refresh at around a few hundred to a few kilohertz.

The ULN2003 mentioned earlier is more than fine for segment drive. Actually, you'd need an octal ULN2803 as a 7-segment display is actually

If this is used to drive the cathode segments you would simply need 8 pnp or pch transistors for the anodes. They don't have to be medium power, even the good old TO92 packs can handle this easily as long as they are low saturation pnps or low RDSon pchs. But to drive the source drivers it is probably advisable to use something like a 74HC138 1of8 decoder to cut down the number of source I/O from 8 to 3. That still leaves you with 11 lines to drive all that though. If you replace the

Personally, I'd just use a character LCD module, it's so much easier. You can drive these with as little as 5 I/O (I done it off an 8-pin PIC). But then again, we are all in the dark (pun) about why you need the display and how you will be using it anyway. This can totally alter the whole design choice.

my2cents

snipped-for-privacy@att.net wrote:

They have them at digikey for about $3. Loooks like that may be the best solution. But the project got put on hold, and customer found something ready made to use, so we don't need them right now.

Thanks,

-Bill