nikisalli

modified 10 years ago

Simple question

172

02:01:57

I have a 74c926 (multiplexing 4 digit counter) and i'm trying to use it with a simple oscillator just for test. It works but the first digit sometimes doesn't count some numbers (every time different) i think is some kind of interference so is there a way to fix that without an external shelding?
-nikisalli

published 10 years ago

faceblast

10 years ago

you have to pull the inputs up or down, see the datasheet. if you leave them floating they will become antennae and start flipping high and low by themselves. put 10nF or 100nF on vcc and ground as close as you physically can to the pins. put 10μF across your power supply lines close to the chip.

nikisalli

10 years ago

I already did that and it didn't work

faceblast

10 years ago

datasheet says: pull latch enable low, reset low. pull display enable high. sounds like latch enable is floating

nikisalli

10 years ago

nikisalli

10 years ago

I connected everything

nikisalli

10 years ago

Only carry out is disconnected

faceblast

10 years ago

dunno then

faceblast

10 years ago

maybe your oscillator falling edge isn't hard enough

faceblast

10 years ago

christ I can't find this chip anywhere

hurz

10 years ago

I also guess its a bad falling edge of clock signal. Add an additional inverter or two to the clock signal.

nikisalli

10 years ago

Ok i will try

nikisalli

10 years ago

@faceblast that chip costs around 16$ or 10€ and i think that they doesn't make it anymore so its really special for me

nikisalli

10 years ago

Hey hurz your method worked very well! You're awesome man!

hurz

10 years ago

Great, but @faceblast told you first ;-)

nikisalli

10 years ago

Yes but you gave me the solution ;-)

faceblast

10 years ago

$16 wtf

faceblast

10 years ago

if you just want to count stuff then do this https://youtu.be/L1FP2NIWj6k

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