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trouble with cd4051/4052 demultiplexers

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aruna1

Member
hello I'm having some troubles with cd4051 and 4052.I'm trying to expand my PIC's output port by using this as a DE-Multiplexer.but it seems not working properly.even though when i give different combination it switch correctly i cant run any output from it(but 4051 output pin shows 5V).

then i tried to do it as a multiplexer.(tried to connect PIC output with a buzzer through multiplexer mode) and then it works.but it doesn't work in de mux mode.

can anyone help me with this?

(i bought two more 4051,and 4052 because i though my first 4052 was burned.but even new ICs give this trouble):confused::(:(:(
 

crutschow

Well-Known Member
Most Helpful Member
Post a schematic.
 

marcbarker

New Member
The 4051 doesn't have a fantastic drive strength at 5V supply. It's 270 to 1000 ohm output resistance. Handy if you want to omit an LED's current-limit resistor, but not if you want to drive something with some oomph.

There must be other better ways of expanding IO's than resorting to 4051's.

Are you sure that there is no other way?
 

aruna1

Member
The 4051 doesn't have a fantastic drive strength at 5V supply. It's 270 to 1000 ohm output resistance. Handy if you want to omit an LED's current-limit resistor, but not if you want to drive something with some oomph.

There must be other better ways of expanding IO's than resorting to 4051's.

Are you sure that there is no other way?
well mystery is how it is able to run as a multiplexer without any trouble.
 
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marcbarker

New Member
well mystery is how it is able to run as a multiplexer without any trouble.
No mystery :) The address control inputs of a 4051(2) are so sensitive that you could put your finger only near one of these (disconnected) pins and it pick up the electrical feild from your finger.
 
Last edited:

mneary

New Member
None of these answers address the issue.

The 4051 and 4052 are not latches. The "multiplexed" output disappears as soon as the address or control signals are changed.
 
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