Hello to all, well i had a nice expirance of submitting the post, on the help of lcd interfacing.... well now i the problem is little bit different...
My problem is that i want to measure the Current (instead of Voltage) using ADC but the problem is that my ADC (or even all the ADCs) are capable of measuring the voltage (0-5v) but i want to measure the current ... so any one have idea how to measure the current...
Well i am working on project in which the current will be displayed on the Computer (in every instance of time) i might be using MAX232 with additional ADC with my 8051 MCU...(using UART) but the main problem is that how do i measure the current :-(
"... so any one have idea how to measure the current..."
Please take the time to think about Ohm's Law:
I = V/R ==> V = IR
What happens when you force some current through a known value resistor?
It is 2 days since made exactly the same post here: " href= "http://www.8052.com/forum/read.phtml?id=133551">www.8052.com/.../read.phtml
As Andy said, you seem not to be willing to think or to get 'help', but want to have a fully working design to copy/paste on.
Hello sir i think i havent posted that thread on Keil.com i have posted that thread on 8052.com
well sir i dont know that is there any relation in 8052.com and Keil... well sorry sir...
You should have realized that many participants of 8052.com are here also. The fact that your post is exactly the same shows that you are fishing for answers, something that lacks netiquette.
"i think i havent posted that thread on Keil.com"
Well somebody using the name "Asif Ali" posted it here on the Keil forum at 08:37 on 25-Feb-2007;
And somebody using the name "Asif Ali" posted exactly the same thing, verbatim, on 8052.com at 3:11 pm on 23/Feb/07
If they really are two completely different and independent people, then my apologies to you. But you must admit that it's a very big coincidence.
"i dont know that is there any relation in 8052.com and Keil"
There isn't - that's why it's important for you to mention that you've posted on both, and to include links, so that people in one forum don't waste their time writing stuff that has already been written in the other forum!
eg, the point about Ohm's Law had already been made in the earlier 8052.com thread.
And you haven't mentioned here that you specifically need AC current measurements...
Well sir i know that OHMs law can be inserted in my problem but sir there is one problems with ohms law... let me mention it...
Sir as i have told that "Known Resistanse and measure the voltage ... you will get the current... I=V/R,,,, right ?"
But sir the problem is just change over here becuz i dont know the resitanse.... becuz do you know that how many resistanse at your main phase line ?? i think that no... (It depend upon your LOAD and some other charectaristics like wire resistanse and so on) but i want to build a Energy meter... which will be doing things digitally. so i am searching for a IC which will give me the measurement of current ...
well sir i think that you might have now understood my idea ... well sir i am really sorry cuz i have opened both of them (Threads) and sir it will never be again...
So accept my applogy.... please
If the measurement circuit doesn't contain a known resistance, you will have to insert an extra resistor of known value into the circuit. The extra resistor will of course have to have a low resistance compared to the normal load, to not adversely affect the current.
The maximum quality of your measurements will greatly depend on how large percentage of voltage drop the extra resistor vill introduce.
If measuring AC current, the current is often measured using magnetic fields instead by the use of a transformer, where the load current is sent through one winding of the transformer, and the resulting voltage is measured on another winding. The problem with transformers is that they have a limited frequency response, so they don't work for DC or for very high frequencies.
"i am really sorry cuz i have opened both of them (Threads)"
So why did you just deny it?
Anyhow, it's not the fact that you opened two threads that's the problem. The problem is that you opened the second thread (this one) without any indication that you had already received a significant number of suggestions in the previous thread.
The result for you, of course, is that you just got exactly the same answer as had already been given in the original thread!
When cross-posting, always include links between the threads
"If measuring AC current, the current is often measured using magnetic fields instead by the use of a transformer"
There are also devices available using Hall-effect, and other techniques.
These have already been explained to you in your original thread on 8052.com: " href= "http://www.8052.com/forum/read.phtml?id=133674">www.8052.com/.../read.phtml
Again, you are wasting people's time as they are just repeating stuff that has already been given to you!
Well sir i have taken your advice and again i will insert the link ... ... well sorry everybody for duplicating the post....
"sorry everybody for duplicating the post...."
The duplication in itself is not the problem!
The real problem is the fact that you have ignored all those people who had already given you plenty of help.
Why have you abandoned the other thread?
You said you would research suggestions made there but, instead, you have just re-posted exactly the same text here without apparently having given it even a moment's thought! You didn't even update it to specify that you need to measure AC!
Well sir i am really searchig for it.... and yes i have only got the basic idea.. speacially i have founded one thing important... "Commercial Current Transformers..." ,,, and there is one more thing interusting... which is "STPM01" ,,, well according to its data sheet.... it can be used as standalone cureent measurer tool... :-)
This is the kind of problem that you solve by use of a multimeter, oscilloscope or similar and not too expensive components on the lab table before starting to wory too much about a uC.
However, there are quite a number of decisions to make before starting on a project. What are you going to measure. What current range. Maximum crest factor allowed. Required tolerance. Expected target price. Frequency range (actually quite connected to the crest factor), how to power the uC, any required isolation of uC from high voltages, requirements to support DC offset currents, ...
Without the above decisions, you can't really design a solution. On the other hand: Are you designing it for yourself or as a commercial product for a company? If it is the later, I would expect you to already have the required knowledge about how to measure, electrical safety, ...
"There are also devices available using Hall-effect, and other techniques"
Since the goal seems to be measurement or integration of AC Power, there is a very elegant approach using analog Hall effect devices: measure the magnetic field with the Hall effect device whilst driving the Hall plates with an AC voltage sampled off the AC line.
That turns the Hall effect device into an analog multiplier, and in effect yields k*ei, or the AC power product.
I have designed a Hall probe that does exactly that, and the results are very accurate.