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Current sensing.

Posted: Sun Jun 10, 2012 5:42 pm
by Creative25
Hi
Is it possible to sense current directly with a pic and a current resistor.
What are the easiest options?
Best Regards:
Uli

Re: Current sensing.

Posted: Sun Jun 10, 2012 8:36 pm
by Steve001

Re: Current sensing.

Posted: Mon Jun 11, 2012 6:17 pm
by Creative25
Hi Steve
This looks like a very interesting current sensor.
Unfortunately in our area I can only get a bare chip.
Is it realistic to solder such a component on my strip board.
Or is there another solution?
Best Regards:
Uli

Re: Current sensing.

Posted: Mon Jun 11, 2012 6:49 pm
by Steve001
Try this one

http://proto-pic.co.uk/acs712-breakout/

I beleve that this is the one that john used in his project

or there is this adaptor-soic-to-dil-8way depends how confident you feel on soldering tho (bit expensive i know)

http://uk.farnell.com/aries/08-350000-1 ... dp/1136592

Steve

Re: Current sensing.

Posted: Mon Jun 11, 2012 7:29 pm
by JohnCrow
Hi
This looks like a very interesting current sensor.
Unfortunately in our area I can only get a bare chip.
Where are you located ?
As Steve said, I got mine from Protopic in the UK, Its orginally made by Sparkfun in the States

Re: Current sensing.

Posted: Mon Jun 11, 2012 9:09 pm
by Creative25
I am Located in Namibia

Re: Current sensing.

Posted: Mon Jun 11, 2012 9:32 pm
by JohnCrow
Hand soldering the device is posible if you have a steady hand, good eyes and a fine soldering iron.

One side of the device (pins 5 - 8) are the control lines. The other side are the current input. The 2 adjacent pins (i.e. 1&2 and 3 &4) are shorted together as
+ve & -ve input.
I think farnell (If they sell in your country) do sell simple BOBs so you could get the chip and 1 of those and make your own version of the board I bought.

Hope you can find something

Re: Current sensing.

Posted: Tue Jun 12, 2012 7:29 am
by Steve001
here it is on sparkfun .

http://www.sparkfun.com/products/8882

Hope this helps

Steve

Re: Current sensing.

Posted: Tue Jun 12, 2012 1:07 pm
by Creative25
Hi to all.
I just browsed the website of Allegro.
The Acs 758 has a larger footprint and I think will be easy to solder. But has a lower resolution.
I think this one is Ideal to monitor my solar batteries.
Best Regards:
Uli

Re: Current sensing.

Posted: Tue Jun 12, 2012 9:24 pm
by Steve001
Hello Uli,

Ther are also these...

http://uk.farnell.com/lem/hx-05-p-sp2/c ... dp/1617420

Or From LEM

http://www.lem.com/hq/en/component/opti ... .08.002.0/

Have used LEM Stuff before they are very good , Hopefully there is a supplier in your country.

Steve

Re: Current sensing.

Posted: Sat Jun 16, 2012 11:35 am
by Creative25
I think I am going for the allegro sensor.
I will order from the US Digi Key has economic shipping options.
I will put a post once I have it working.
Best Regards:
Ueli

Re: Current sensing.

Posted: Wed Sep 19, 2012 12:49 pm
by Creative25
Hi to all.
My current sensor ACS712 has arrived and I made my own board unto which I soldered it.
It is very easy to implement.
Especially with a reference voltage of 4.096volts then the formula is easy.
According to the data sheet it has an accuracy of 1% which is fine.
Just a pity they do not have a 10A sensor so I had to use the 20A sensor.
With a 10A sensor the reading would be exactly twice as accurate.

When you disconnect a load the reading is slightly above zero, but after a few seconds it goes exactly back to zero.
But still it is within 1%
So I guess this is because of self heating of the sensor. I think it would help to add a copper area to the pad so the chip does not warm up.
Best Regards:
Uli

Re: Current sensing.

Posted: Wed Sep 19, 2012 1:32 pm
by Enamul
Hi Uli,
This is a nice current sensor. I haven't noticed that earlier. Did you use that earlier or the first time you have ordered this? How reliable is this sensor in terms of life span? Is that suitable for commercial products for current metering or even energy metering?

Re: Current sensing.

Posted: Wed Sep 19, 2012 2:03 pm
by Creative25
Hi Enamul.
I can not say anything about reliability because I just have tested it for a few minutes.
I guess I will have to use it for a year or so before I could say it is reliable.
I guess with an Guaranteed accuracy of 1% it is not good enough for a commercial meter.
Except you create some firmware for more precise reading.
In my circuit I plan to use it for energy budgeting for this purpose it will be good enough for me.
Best Regards:
Uli

Re: Current sensing.

Posted: Wed Sep 19, 2012 2:08 pm
by Enamul
You are right. Thanks a lot. I will try one and see how far I can get from it.

Re: Current sensing.

Posted: Wed Sep 19, 2012 2:22 pm
by Creative25
Let us know if you find a way to improve accuracy.
Best Regards:
Uli

Re: Current sensing.

Posted: Wed Sep 19, 2012 6:20 pm
by Steve001
Enamul wrote: Is that suitable for commercial products for current metering or even energy metering?
there is a application note on microchip site

http://ww1.microchip.com/downloads/en/A ... f?from=rss

and another one here

http://dev.emcelettronica.com/single-ph ... crocontrol


for DC circuits i would look at LEM devices (They are a tad expensive but good) or a mv shunt calibrated to suit IE 200A = 75mv

http://www.lem.com/hq/en/content/view/268/205/



steve

Re: Current sensing.

Posted: Tue Dec 04, 2012 10:46 am
by ingobauer
caisses enregistreuses

Triple-channel device with digital interface allows for monitoring three separate voltages, eliminating the need for discrete devices for each voltage
High accuracy: 80 ┬ÁV maximum offset voltage and 0.5% gain error enable high peak current detection
Integrate into applications with increasing common-mode voltage ranges: Common-mode range of 0 to 26V, supply range of 2.7 to 5.5V, and 160 mV maximum shunt
Performance optimization under multiple operating conditions: Configurable alert monitoring scheme, programmable sample averaging, and independent bus and shunt voltage conversion times

Re: Current sensing.

Posted: Wed Dec 19, 2012 3:12 pm
by Steve001
here are a couple more currrent sensors IMAG0075 is a LEM HTFS 200-P it's a 200 amp hall device that i am planning to use within a project that i have lurking but unfortunately i haven't has the time to do much work on it :(

IMAG0073 This is a 2500:1 current transformer which is fed into a bridge rectifer circuit and resistor which is set to give 2.5 volts out at a set current have used this in a project and it worked well

IMAG0057 is for the people that wish to go the "whole hog" this is a 7000:5 current transformer that we use at work . . . stupid things :roll:

Steve

Lem data Sheet

http://www.lem.com/docs/products/htfs20 ... _rev09.pdf

Re: Current sensing.

Posted: Wed Dec 19, 2012 3:16 pm
by Enamul
Hi Steve,

Did you use your own custom made board after CT or any ready-made board to interface with microcontroller?

Re: Current sensing.

Posted: Wed Dec 19, 2012 5:27 pm
by Steve001
Hi Enamul

Its a custom PCb that did and had made by pcb train it's got other stuff on ther too A MOC3021 and a BTA18 triac wich was going to be used as a "soft start" and a couple of relays, It was in project for work which got mothballed it was on here but i got asked to remove it so i cannot post too much about it but i am willing to help you with it if you want.


Steve

Re: Current sensing.

Posted: Fri May 10, 2013 8:34 pm
by Steve001
Attached a prototype pcb and manufacturing files for the above Lem current sensor
Pcb designed in eagle 6.1.0

had it lurking on hard drive just decided to finish it off , hope someone finds it usefull

THE HOLE IN THE CENTER OF THE HTFS 200 SENSOR WILL REQUIRE OPENING OUT TO 20mm 4mm PIOLT HOLE ON PCB


Steve

Re: Current sensing.

Posted: Sun Jun 09, 2013 7:31 pm
by Steve001
after having a tidy up today i found these two current transformers that the rep gave me from one of our suppliers from work to play with for a project.

The blue one has the following markings on it

NCT-07
5(6)A - 330mA
Class 0.1
http://www.hzknowhow.com

Unfortunateley i cannot obtain a data sheet for it :(

which is a shame as they also make this with a 330 mV output this has a distinct advantage with a voltage output rather than current , the issues with open circuit current transformers are elminated with this device.

The grey one is from ITACOIL
part number 1000506/B
5(6)A - 330Ma

But but ITACOIl wanted MASSIVE order quantities 1K + this made it difficult to decide to use :(

Hope this info is of some use

Steve

Re: Current sensing.

Posted: Mon Jan 06, 2014 9:57 pm
by Steve001
Found this application note about current sensing whilst looking for something else

http://cds.linear.com/docs/en/applicati ... /an105.pdf

steve