Project on measuring the power my home uses

[DrShoe]

lem la 55

The idea is to measure the power my home uses, store and analyze later with a PC.
A digital power meter with pulses per watt should be handy for this but I have a analog one with rotating disk.

What I want: The incoming phase of my home into a LEM current sensor (LA 55-P) to measure the current.

The voltage is not measured only the zero crossing.

From a zero cross, sample the current for 20mS and multiply it by the voltage from a lookup table.

The advantage of this system is that no switching analog ports is needed.
What is the maximum sample rate with a 16F876 10 bits.?

AD7755 is also possible but the current sensor is difficult to place and I like to this with own made tools.

Any ideas? any did this already?

 

[flatulent]

two thoughts

It would be easier if the output of your sensor was processed with analog electronics and that signal fed to your computer. You could bridge rectify the output and filter it with a capacitor to get a voltage related to the current. This assumes that the diode drops were small compared to the signal level or you corrected for this in your computations. If you were not too particular about accuracy, you could assume an average line voltage in your processing. Of course this will not take power factor into account. If all you are interested in is the 24 hourly cycle of power usage this may not be a problem.

The main problem is safety. You will have to disconnect the main wiring to your house to put them through the sensor center.

 

[dacadc]

Energy metering

You can use:
1. Analog Devices Chips
2. Crystal Chips
3. PSoC processor, it is reference design for it

 

[korek]

Hi,
You can also check SAMES chips. Power measurement is their specialty.
https://www.sames.co.za/

 

[dacadc]

Sames

I tested Sames. The ADI and Crystal are in times better! So I cannot advice to use Sames

 

[marie65]

Re: Sames

I tested Sames. The ADI and Crystal are in times better! So I cannot advice to use Sames

Can you detail why ADI and Crystal are better than Sames? I just want to begin a project with the Sames chips and I'm interest by your experience with this chips.

 

[marie65]

Re: Sames

I tested Sames. The ADI and Crystal are in times better! So I cannot advice to use Sames

Can you detail why ADI and Crystal are better than Sames? I just want to begin a project with the Sames chips and I'm interest by your experience with this chips.

 

[bunalmis]

Re: Power measurement

Lem sensor good choice for current measurment. You can use small
isolation transformer for voltage measurment.

Dont forget P not equal the V*I

You must find the cos Q power factor.

 

[okguy]

SAMES is poor on its spec (ESD, variations, ...)
Just check all datasheets: you will understand !

OkGuy?

 

[nukhung]

Hi,
You can also check SAMES chips. Power measurement is their specialty.
https://www.sames.co.za/

Please advise me where I can order a few SAMES chips, I have contacted SAMES but they don't reply.

 

[DrShoe]

Analog Devices

The best solution for me came from Analog Devices the ADE7755.
I've received two samples. Changed the application note a litte for using my LEM sensor.

 

[FANT]

Power measurement

If you are using this project for your home aplications is everithing OK, but if you intend to use it as a measuring instrument or even worst for business, take a lot of care about the safety of your instrument, consider ( if you are in the EEC area ) that there are many rules to be followed about something applied to the mains ( overvoltage protection, aovercurrent protection, galvanic insulation, IP grade protection.
If this is the case, you can contact me ( PM or directly here ) if you need some informations.

Don't forget that everithing connected to the manis ( except plugs ) must be marked CE and follow the 73/23/CEE directive.

Mandi

 

[VSWR]

Re: Power measurement

The ADE7752 is a high accuracy three-phase electrical energy
measurement IC.

You can use simple clamp-on type current transformers on each the incoming three phase wires. No need for changes in your houses electrical installation (could be dangerous).

 

[nukhung]

Hi,
Chipset Solution for Watt-hour Meters.
AT73C500 & AT73C501 from Atmel

 

[Sobakava]

Atmel Power Measurement is obsolete

Atmel finishes his power measurement/analysis line.... AT73C500 & AT73C501 are obsolete now.

 

[superben]

cs5460

How about cs5460?

It can be used to measure voltage, current, active power, power factor, frequency and test watt-hour

 

[mario1980]

Re: Power measurement

Not an answer to your problem, but since you are somewhat interested in this matter you should consider the possibility of turning off the power of the whole house, during the night. The reason is that electromagnetic fields are not so good for human beeings, especialy frequencies about 50Hz affect memory. I have heard of such houses that have the possibility of switching off power during night and not only.