Pages: [1]   Go Down
Author Topic: CD74HC4067 Multiplexor. Is Resistor important?  (Read 2173 times)
0 Members and 1 Guest are viewing this topic.
0
Offline Offline
Newbie
*
Karma: 0
Posts: 12
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

hi everyone

just a quick question, specifically about a multiplexer but may just be a 'rule of thumb' for many ICs

with the  CD74HC4067E PDIP

Ive got a 100nF cap accross the power  

but do i need a resistor along the 'enable pin to ground' connection

the schematic on the single SMD CD74HC4067 board here:  http://www.sparkfun.com/products/9056
has a 10k resistor

but the same chips here on a 3 chip board dont: http://mayhewlabs.com/products/arduino-mux-shield

is this resistor important??

tried searching and people mention building your own mux ect but no specifics on the resistor

thanks everyone
Logged

Manchester (England England)
Offline Offline
Brattain Member
*****
Karma: 602
Posts: 33362
Solder is electric glue
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Logic chips like this can have the pins directly connected to either voltage rail. However a 10K to ground makes it look like a logic zero but allows you to easily pull it high later if you want to connect a signal to it.
« Last Edit: November 07, 2011, 08:19:40 am by Grumpy_Mike » Logged

0
Offline Offline
Newbie
*
Karma: 0
Posts: 12
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Thanks! so I know its not essential, I'm just going to connect them direct to ground for now, as thats ok

but if I decide I want to enable/disable the chips for some reason, I add a resistor to ground ( is 10k enough for two chips?)  so its enabled by default but use a 5v 'digital out pin to 'HIGH' to this enable wire to dissable the chips?

have i got that right?



* IMAG0554.jpg (537.76 KB, 1549x1921 - viewed 32 times.)
Logged

Manchester (England England)
Offline Offline
Brattain Member
*****
Karma: 602
Posts: 33362
Solder is electric glue
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Yes that is right.  smiley

Quote
( is 10k enough for two chips?)
Well if it was me I would use 1K resistors to pull down.
Logged

Pages: [1]   Go Up
Jump to: