DIY_EFI Digest V6 #49

[Carter Shore]

On Sat, 15 Feb 1997 20:37:47 <nacelp at bright.net>
wrote:

> Will a 4017 drive a single LED thru a 1K resistor on
> 12v, OK?. 

Driving LEDS directly from 4000 CMOS is always a bit
dicey. The spec is around 3-4 mA for most logic chips,
higher for those intended for buffer usage.

It will probably work OK, but the LED light level will
be dim. There will also be a bit more heat generated
in the chip than normal, because the output stage will
be operating in the linear region. But not a whole
lot, probably no more than 50 mW. Is the 4017 in a
socket?

If this is on a breadboard, I'd look into adding a
spare 4049 or a 4050. These are hex buffers, able
handle a bit more current (25 mA I believe). And the
gates can be hooked in parallel for more drive
current.

Otherwise, a 2n2222 transistor is probably the
simplest and easiest way to drive the LED.

Carter

__________________________________________________
Do You Yahoo!?
Yahoo! Sports - Coverage of the 2002 Olympic Games
http://sports.yahoo.com

----- End of forwarded message from owner-diy_efi at diy-efi.org -----
----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org