Power Line loging.

[jcon777]

What is the best and most accurate way to constantly read the utility power voltage and ampere usage. I need to send them out to LCD on 4 data line and out to a serial line using 16F873. I am using PBP.
Please send me the circuit with pbp code .

Thanks.

[NavMicroSystems]

@jcon777

Are you kidding?

Are you really expecting to receive a full blown solution?
(schematic and ready to run code)

I guess Mel would say:
"You have got to do some homework"

If you tell us how far you have got so far
we will certainly be able to help you figuring out some details.

rgds

[jcon777]

of course I did a lot of work, but did not get good result, this why I am asking for new ideas .
I used 2 limiting resistors connected to a bridge with a divider resistors on the output with a cap as a filter.
Somehow I am not getting a stable result.

Thanks.

[NavMicroSystems]

Am I right in understanding you are trying to measure mains (AC) voltage and load using a few resistors and a capacitor?

[CBUK]

if that was so, i think you could assume 2 puffs of smoke for correct operation, one for under voltage, and 3 puffs for over voltage. surely the easiest way would to be by using a transformer to drop the line voltage by a ratio of the windings, and as for the current the use of a CT coil around the live conductor to give a mili-amp current for the ratio again. then what you have to ask yourself is are you going to display the values in the RMS value (the useful value) or the mean value..... why are you wishing to do these measurements?!?! to make KWh meter or something??

Chris

[NavMicroSystems]

@ CBUK

we are all guessing.

let jcon777 come back with some more details before we continue this thread.

rgds

[Dwayne]

Hello Jcon,

Jcon>>of course I did a lot of work, but did not get good result, this why I am asking for new ideas .
I used 2 limiting resistors connected to a bridge with a divider resistors on the output with a cap as a filter.
Somehow I am not getting a stable result.<<

Well, a couple of things... you will get various readings. Every time you turn on a appliance, your voltage will drop. The Voltage will increase if you turn off a appliance. And depending upon how much current that apparatus has, you will have larger swings in voltage.

A cheapy way how to measure voltage, can be with two resistors, in series, valued at about 1/12 or so. Then run through a Bridge to Pulsate to DC. But if you use a capacitor, you will run into the problem of seeing the "Fluxuations".

With this in mind, you can use a comparator and constantly sampe the output...And as soon as the output starts dropping, you know your maximum voltage... and print that out to the LCD. then continue sampling until it starts to increase and peaks.

With a duel trace scope, you can monitor the input voltage and the output voltage.. and have a "converstion" factor. If its 120 volts in, and the peak after the Bridge is 4.5...then 0 volts is equivalent to 0 after your bridge... Solve the equations simtaniously, and get a equation like converting Cel to Far.

Realizing that the Voltage drop from 120 down to whatever will add a negative accuracy factor to your answer. But that small amount may not be a that big of a deal for you...

Either way, give us a idea what you are doing... show us a diagram...Some code... or both. A person can't expect to come on a forum and say "Give me this" or "Give me that" with code, schematic, and the works. I am sure this was not your intention. I think what you really wanted to say, is that your way or method of getting the data you wanted is not working well enough, and you need help in thinking of another way to do it. Or maybe you have no idea how to go about it, and need help in that direction.

Either way, Try posting another thread with your idea, what you have drawn up that works (or doesn't work), Tell what kind of outcome is happening, and ask if there is another way to accomplish the task a little better with everyday common parts. Add a schematic to the Thread, and Add your PBP code too. I am sure there are *many* folks (including myself) who will look at the info and say "This is good, but it may be more accurate and cheaper to do it this way".

I have asked for help a few times, and have had some beautiful reponses on ideas I never thought of. (Thanks Guys and Gals). Things like this is what makes a forum successful. I came from the Philips Microchips...ASM only... UV lights, and 25 min burn time... YUCK!. I am now hooked on these PICS, and have learned much about them... and have MUCH more to learn.

Dwayne

[CBUK]

i would just like to add from a UK point of view that using resistors directly on the mains supply is a very dangerous thing to do because effectively your pic circuit will have potentially 'live' parts that have no isolation from the power line.
also dwane, you say the voltage will vary when an appliance is turned on, yes it will but only by mili volts, in the UK we have a tolerance of 4% for voltdrop in an electrical system, so if the voltage is dropping beyond this then there could quite possabily be a problem in the mains supply. another thing to consider is large current drawing appliances such as tumble dryers/ electric heaters/ fridges will cause surges and spikes on the mains when switching in and out. if you do not have sufficient protection to snubb these surges and by using just resistor voltage deviders straight into the pics then they are just going to go pop! the other thing that you have demonstrated for example the 1/12 ratio and getting 4.5 volts out after silicone rectification for 120 volts then this doesn't really give enough resolution of scope to measure small varying changes surely?!

[Dwayne]

Hello CBuk,

CBUK>>i would just like to add from a UK point of view that using resistors directly on the mains supply is a very dangerous thing to do because effectively your pic circuit will have potentially 'live' parts that have no isolation from the power line.
also dwane, you say the voltage will vary when an appliance is turned on, yes it will but only by mili volts, in the UK we have a tolerance of 4% for voltdrop in an electrical system, so if the voltage is dropping beyond this then there could quite possabily be a problem in the mains supply. another thing to consider is large current drawing appliances such as tumble dryers/ electric heaters/ fridges will cause surges and spikes on the mains when switching in and out.<<

yes, you are correct... Diodes can help in this area...


I was playing around with a Car Gas Pump with a friend of mine... we connected it to a PWM via a MosFet to control its speed. Found the MosFet getting very warm at low speeds, and very cool at high speeds. The motor was drawing about 1 amp. The MosFet was rated at 10A when sunk. Measuring voltage, we had spikes in the 50 Volt range and higher...

Put a diode across it, and the MosFet cooled down like it was supposed to...Solved the heat problem <g>.


CBUK>> if you do not have sufficient protection to snubb these surges and by using just resistor voltage deviders straight into the pics then they are just going to go pop!<<

Yip! you are correct....

I am just trying to figure out what the Gent wants to do, and how. I think MicoNavigateSystems has the right way how to think... What DOES he want. We can only assume, guess, and make broad assumptions, unless he gets more detailed.

I was only hoping to encourage him to try again. I am thinking that what he said was not what he meant. Sometimes in these computer forums, what comes across is not what we mean, because we cannot see the Body Language of the person talking.

Dwayne