Digital multimeter using 8051

Hello,

I am trying to build a digital multimeter that can measure dc/ac voltages up to 100V and dc/ac currents up to 1A. The circuit will be powered by 9v battery. I have decided to use the voltmeter from

http://www.8051projects.net/download-d214-simple-digital-voltmeter-using-8051.html

and modify it according to my needs. The problem is that after implementing the circuit, I only get half the value shown on the lcd (10v input ,5v on lcd)[SOLVED: I was suppose to connect to vcc not Vref/2]? What could be the reason for this?

For extending the circuit to 100v I was going to modify this line:

 "adc = adc_avg * 59" to " adc = adc_avg * 390"

according to the instructions from here:

http://www.8051projects.net/lofiversion/t28770/clarification-code-used-for-digital-voltmeter.html

is this correct?

Here is the project file in "Proteus":

http://www34.zippyshare.com/v/42983743/file.html

For extending the circuit to 100v I was going to modify this line:

 "adc = adc_avg * 59" to " adc = adc_avg * 390"

I works until 65.5v from then on it resets; for a source of 70v it displays 3.88V.

johndorian( in chat box)

The problem is due to adc being a 16 bit integer, so can't hold a result greater than 65535.
168 * 390 is okay
169 * 390 is not.

Probably the best solution is to multiply by 39 and divide by
100, not 1000 later on.

Remember that using an 8 bit converter you can't measure in the 100 volt range to better
than about 0.4 of a volt

thank you @Experimenteruk everything works perfectly. Now I have to add a rectifier so I can measure AC voltage and current. I am going to post the finished project when it's all done.

For now, here is the voltmeter that can measure up to 100V

http://www9.zippyshare.com/v/97496860/file.html

Hi, I'm new here. I want to modifie the digital voltmeter project into a multimeter to measure 0-100 V AC and DC and 0-1 A. How can I modifie the c code to display on the LCD AC, DC, A, V?
Here is my project. Now it is measure only 0-100V DC. Please HELP!

We are in the same class! 2032 Rares

@johndorian
i want this projected. can u please mail this to me at [email protected]

@ pyka312
u need change in hardware as well as software
AC measurement is not an easy task
@ raza.majeed
ur registered member here so u can download it in download section instead of saying anyone to mail u

while not use ic7107 digital voltmeter @ http://www.intersil.com/data/fn/fn3082.pdf all you need to know is there

here is the circuit diagram of the above requiest,no microprocessor can handle that but this chip can handle upto 2000v maxinium both dc and ac

yes that are dedicate chip for this purpose