Using CD4051 to multiplex AC 50hz sinewave analog signals

[lats]

CD4051 ac signals?

hi,
can i use cd4051 (analog multiplexer) to multiplex AC 50hz sinewave analog signals or can only dc analog voltages be multiplexed?

 

[IanP]

Re: CD4051 ac signals?

Be aware of one thing: if the input voltage peak-to-peak is symmetrical about (Vdd-Vee)/2 then it doesn't matter ..
Next if, if the supply voltage is 0-5V (or 0- whatever below Vdd-Vee MAX) it means that the AC input voltage average value has to shifted to 1/2 of the supply voltage, in this example 2.5V ..
As you are cosidering connecting AC voltages it is wiser to convert them first to DC and then feed them to CD4051,
or,
supply CD4051 of +/- symmetrical voltage, say +/-5V (Vdd, Vee) and Vss=0V, feed AC signals directly to CD4051, and convert the output signal with one AC/DC converter ..

Entirely our choice ..

Regards,
IanP

 

[lats]

Re: CD4051 ac signals?

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[IanP]

Re: CD4051 ac signals?

.. So should i feed these three analog voltages (0 - 0.1 v) to a analog multiplexer ..

This 0.1V rms is within the input voltage range of the CD4051, so I think you can connect signals from current transformers directly to CD4051 [use 2 protective diodes at each input, one connected between input (Anode) and Vdd (Cathode) and one connected between the same input (Cathode) to Vee (Anode)], then to peak detector, and so on ..
By doing so you will be having only one peak detector in the whole circuit ..

Regards,
IanP

 

[lats]

Re: CD4051 ac signals?

By doing so you will be having only one peak detector in the whole circuit ..

ya this is only the purpose to use single peak detector to reduce the cost.

next, as u said in previous reply

supply CD4051 of +/- symmetrical voltage, say +/-5V (Vdd, Vee) and Vss=0V, feed AC signals directly to CD4051, and convert the output signal with one AC/DC converter ..

will i need to feed +5 and -5 volts to cd4051? and for protection diodes will 1N4148 do?

Thanks

 

[IanP]

Re: CD4051 ac signals?

I think you should use +/-5V as Vdd and Vee ..
After all, I guess, you will be using symmetrical supply voltage for peak detector, won't you?
In this case 1N4148 diodes are just fine ..

Regards,
IanP

 

[Prasad Aritakula]

Re: Using CD4051 to multiplex AC 50hz sinewave analog signal

Hi,

I too have a similar requirement. Can I use +3.6V/-3.6V as Vdd/Vee ? The max.
ac signal (pp) to be muxed is less than 0.5Vac. and I am using microcontroller
output pins having logic level of 3.6V to drive the channel selection.

Regards,

 

[karesz]

Hi Prasad,
Because the 4051 are specified for Vdd between 3---18V , of course; you can apply +/- 3.6V (insteed +/- 5V) for your device.
Greetings!
K.