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01-28-2010, 06:31 AM
I'm using BS2 (board of education) and need to read DC voltage between 0-40 for my solar power project and nee a guide line.
cheers

JD
01-28-2010, 07:39 AM

How much resolution or precision do you need? For example, do you need high resolution like 2.5 V or something more lenient such as integer voltage only.

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Respectfully,

Joshua Donelson
www.parallax.com (http://www.parallax.com)

01-28-2010, 06:31 PM
One decimal in enough

01-29-2010, 04:14 AM
Sorry, I mean Yes and high resolution is required

JD
01-29-2010, 04:24 AM

It would be possible to use a voltage divider to get the voltage to a useable range,·then put that output into a ADC, and then take the reading output of the ADC and multiple it by the same quantity to get the 0-40 range back.

For example, if you divided the voltage by 10 (9k/1k voltage divider), that·output to the ADC input,·then multiple the output of the ADC by 10 to get the appropriate 0-40 voltage. That should give you a 0-40 with 1V per division. Would·that be enough resolution? What is this project for?

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Respectfully,

Joshua Donelson
www.parallax.com (http://www.parallax.com)

01-29-2010, 03:50 PM
Yes that would be adequate. The BS2 would be the heart of a solarcell system; read light intensity and position cell board accordingly.

I know it can be done with a simple circuit without involving BS2, but I also need to monitor voltage output of the cell among other data (like temp. and wind speed) and log the data into a computer via vb.net application.

I guess I can find a voltage divider diagram within the forum.

Thank you Joshua.

01-29-2010, 04:43 PM
Pls. forgive my ingnorance as I'm not so good in electronics.

I have a maximum of 40Vdc to measure and need a diagram for connecting an ADC (which type) to BS2.

rgrds

Mike Green
01-29-2010, 09:45 PM
Read the Wikipedia article on voltage divider for a diagram, formulas, and a detailed explanation (do a web search for "Wikipedia voltage divider").

JD
01-30-2010, 12:00 AM

Since you only need integer numbers then you should be able to use an 8-bit ADC (ADC0831) and you could use the BS2 you already have the Board of Education. As for a diagram, Mikes suggestion will help greatly to figure out the output of the voltage·divider.·Once you know the wiring of a voltage divider, you would take the output and put that into the input of the ADC; reference the datasheet for the correct physical pins to connect. For example for the ADC0831, pins 2 and 3 is the input from the voltage divider. I hope this helps

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Respectfully,

Joshua Donelson
www.parallax.com (http://www.parallax.com)

01-30-2010, 05:17 AM
So a voltage divider is needed because the ADC0831 cannot READ more that 5Vdc on pins 2 and 3. If this is true, then I'm off to order the part and try it.

If R1=1K and R2=140 then Vout=4.912 .... So all what I need now is a code to get data from ADC and then play with a formula to get the orijinal reading.

JD
01-30-2010, 05:31 AM

Excellent, when you are done you can post in the completed projects forum; it's always nice to see members projects completed.

Parallax Forums [ completed projects ]:
http://forums.parallax.com/forums/default.aspx?f=21

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Respectfully,

Joshua Donelson
www.parallax.com (http://www.parallax.com)