The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
X-Mailer: Mozilla 4.75 [en] (Win98; U)
Subject: Re: TTL/LS registers driving LEDs
Date: Sun, 15 Dec 2002 04:25:26 GMT
NNTP-Posting-Date: Sun, 15 Dec 2002 15:25:26 EST
Organization: BigPond Internet Services (http://www.bigpond.net.au)
You can drive them directly, as long as you are sourcing current. I've
done this from both 5V and 3.3V devices. In general though, to avoid
unnecessarily stressing the devices, I add a small series resistor to
limit current. The LEDs are still bright enough for daylight.
Jem Berkes wrote:
> I'm working on a little digital device (TTL based) and am going to need
> some 8-bit registers to drive LED displays. I might be building a lot of
> registers into this and wiring is difficult (no automation) so I've been
> trying to figure out whether it's OK to drive a small 7-segment LED display
> directly from the outputs of, for example, the 74LS374 instead of adding
> more buffers. Datasheet: http://www.fairchildsemi.com/ds/DM/DM74LS374.pdf
> It sounds like that register is built for driving bus lines but I don't
> have enough experience to judge whether it's OK for driving small LEDs.
> Jem Berkes
> Windows, Linux & UNIX software
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup