help with ad9875

[Stijn Goris]

hi all,

I want to sample the powerline via the AD9875 (datasheet:
http://www.analog.com/UploadedFiles/Data_Sheets/62024329AD9875_a.pdf). I
have little knowledge about electronics so I need some help here .
When I want to sample the powerline I have to go from 220 - 230 (Europe) to
4 Volt (I think). Does someone knows how I best achief this (a diode)? Do I
need to adjust the input signal other then aletring the voltage. Maybee I
neeed to use some filtering?

Thanks in advance
Stijn

 

[Ilkka Karaila]

"Stijn Goris" <mepisto@hotmail.com> wrote in message
newsIxnc.101032$Zf4.6228066@phobos.telenet-ops.be...

hi all,

I want to sample the powerline via the AD9875 (datasheet:

For what purpose?
What is the informtion you are looking for?

http://www.analog.com/UploadedFiles/Data_Sheets/62024329AD9875_a.pdf). I
have little knowledge about electronics so I need some help here .
When I want to sample the powerline I have to go from 220 - 230 (Europe)
to
4 Volt (I think). Does someone knows how I best achief this (a diode)? Do
I
need to adjust the input signal other then aletring the voltage. Maybee I
neeed to use some filtering?

You need a voltage divider, with division ratio about 100. Put in series 1
Mohm and 10 Kohm resistora with power rating (wattage) over 0.1 W
dissipation and take the signal from the terminals of the 10 kohm resistor,
the other end of tha t resistor must be connected to the power zero of the
AC-line..


I did not have time to study the IC-specifications, so my advice is vey
tentative.

 

[mike]

Stijn Goris wrote:

hi all,

I want to sample the powerline via the AD9875 (datasheet:
http://www.analog.com/UploadedFiles/Data_Sheets/62024329AD9875_a.pdf). I
have little knowledge about electronics so I need some help here .
When I want to sample the powerline I have to go from 220 - 230 (Europe) to
4 Volt (I think). Does someone knows how I best achief this (a diode)? Do I
need to adjust the input signal other then aletring the voltage. Maybee I
neeed to use some filtering?

Thanks in advance
Stijn

Depends on what you want to achieve. A diode/cap/voltage divider will
give you the peak voltage.
Now, what are you gonna use as a ground reference for the A/D? without
killing yourself...
A transformer is one way to go. A 3-20VDC or so wall wart is a good
place to start. Xformer, diode, cap all ready to go.
Remember that this system will respond to the peak voltage...sort of...
'cause the cap integrates.
depending on noise, spikes, glitches on the waveform, you may or may
not be measuring the thing you want.

Food for thought:
If you run the AC (divided down, of course) into the A/D and sample
randomly, the statistics of the samples will be the same as the
statistics of the waveform (yes, you have to sample frequently enough
to get a statistically significant sample). So the
peak/average/rms/anyotherstatistic values of the sample set will be the
same as the sampled waveform.
mike

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[Stijn Goris]

"Ilkka Karaila" <ilkkaNO.karailaSP@AMpp.inet.fi.invalid> wrote in message
news:Oxync.330$cv1.21@read3.inet.fi...

"Stijn Goris" <mepisto@hotmail.com> wrote in message
newsIxnc.101032$Zf4.6228066@phobos.telenet-ops.be...
hi all,

I want to sample the powerline via the AD9875 (datasheet:

For what purpose?
What is the informtion you are looking for?

http://www.analog.com/UploadedFiles/Data_Sheets/62024329AD9875_a.pdf). I
have little knowledge about electronics so I need some help here .
When I want to sample the powerline I have to go from 220 - 230 (Europe)
to
4 Volt (I think). Does someone knows how I best achief this (a diode)?
Do
I
need to adjust the input signal other then aletring the voltage. Maybee
I
neeed to use some filtering?

You need a voltage divider, with division ratio about 100. Put in series 1
Mohm and 10 Kohm resistora with power rating (wattage) over 0.1 W
dissipation and take the signal from the terminals of the 10 kohm
resistor,
the other end of tha t resistor must be connected to the power zero of the
AC-line..


I did not have time to study the IC-specifications, so my advice is vey
tentative.

I 'm designing a product for a school assigment. I don't realy have to build
it but neverteless have to make a detailed study about the what components
are needed. I m making a product bases on the Cogency Piranha chipset.
(http://www.cogency.com/B_Support/2pg_Product_Brief_Piranha.pdf - powerline
communications) I 'm wondering what components I need to give the AD9875 the
correct input.

kind regards
Stijn