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windman1000
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Posted: 06 April 2011 at 12:03am | IP Logged Quote windman1000

Hi
I found this Hall-Effect Current Sensor On Ebay Link

PDF PDF LINK



Can this take the place of Shunt on the piclog and if so do I hook the +supply to the regulator 5v Side Of piclog, Ground to Ground Of piclog, ADC to the ADC picaxe Chip But leave inline the 1k resistor and the 0.01uF Cap?

And if this is ok to use as the shunt do i need to change anything in the Picaxe Code?

Thanks
Windman

EDIT Im trying to get the AMPS more Stable / linear

Edited by windman1000 on 06 April 2011 at 12:18am



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fillm
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Posted: 06 April 2011 at 8:24pm | IP Logged Quote fillm

Hi Windman

Looks identicial to the Allegro current sensors I use, mine are 50A/ 5v and they work very well .

Seems like a good price as mine were double that price and didn't have the printed board mount. Might even get a couple for spares .

You may have to make a couple of changes to your circuit , I am not the Giru with this stuff .
Zero usually runs at around 510 and I did have a lot of trouble with counting backwards slowly but I think in the latest program it has been fixed .







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Posted: 06 April 2011 at 9:04pm | IP Logged Quote Gizmo

Hi Windman

Yeah Phills right, that's just like the Alegro chips, at a good price.

I am running a Alegro on my PicLog now. Its currently monitoring a batter bank thats powering a few garden lamps, with a smart battery charger to keep it charged, so not very exciting.

My main computer is down, so I cant dig up the changes I made to the circuit for the Alegro. I think I just fed its output pin directly into the PicAxe, where the shunt was connected. I need to go out to the shed and have a look tomorrow to check. I think the latest software worked fine, and it does include some filtering to get rid of the stray readings.

Once I get this PC running again I'll dig up more info.

Glenn

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windman1000
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Posted: 06 April 2011 at 10:50pm | IP Logged Quote windman1000

Thanks Guys
I Received this in the mail less than 12 hours after buying it (WOW)
I took an extra piclog board I had and hook up the current sensor like I explain above
and zero the 510X to 0X with no current flowing , Now waiting for some wind to calibrate the amps , If everything goes right Il buy 3 more and use them on my new 14M X 4 Piclog Project LINK

Thanks
Windman

Edited by windman1000 on 06 April 2011 at 10:51pm
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Alasdair
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Posted: 10 April 2011 at 9:27pm | IP Logged Quote Alasdair

Hi there
it would be a good idea to run it's output through an op-amp
even at unity gain, with some filtering before feeding into pic,
you can immunize against supply fluctuations giving bogus
readings and vary the gain if needed for more sensitivity.
You may also need to test for linearity across the range if you
want good accuracy, and correct any deviation in the code.
Regards Alasdair.

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sjh7132
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Posted: 27 December 2011 at 2:05pm | IP Logged Quote sjh7132

I used a part that looks just like this in my MPPT controller design. Mine was the Allegro ACS758. Mine are bidirectional devices, so 0 amps is an output of 2.5v. If yours are the same you will want to put an opamp circuit after it to bias the voltage down and give you a 0-5v output over your current range.

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Posted: 28 December 2011 at 5:38am | IP Logged Quote norcold

Have four of these sensing my mills output with the SC USB data logger, they require a very stable and precise voltage supply or their readings are way out. Currently am using connected to an external powered USB hub and am pretty happy with results. My findings are they each must be calibrated seperately and their script adjusted individually with a known meter, if not their readings are meaningless. From my experiments and opinions from others it seems shunts are more accurate( this is not a final opinion only one I am at this stage) Will be comparing this with a shunt logger I didn`t realise I had until a recent discussion I had with my solar installer. My Selectronics inverter with Energy Maintenance Mark 11.

Edited by norcold on 28 December 2011 at 5:39am


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Posted: 28 December 2011 at 7:42pm | IP Logged Quote fillm

Hi Vic,

Yes they are noisy and you will need a filter , cap and resistor to smooth them out but it also slows them down a little. From what I have seen the picaxe data they usually 0 between 508 to 514, and without filtering will be up and down 2 to 3 which then can keep adding or subtracting Ahrs depending where the zero is set, with Glenns Piclog2 program you can also add some filtering in the software . As you have gone down a road that no-one has been down here that I know of it does leave you a bit alone with your logger but it sounds like you are getting there.

After getting the zero set I calibrate mine to the PL60/PLS2 current shunt which is fairly accurate and I have also found each one is a little different.

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VK4AYQ
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Posted: 28 December 2011 at 8:14pm | IP Logged Quote VK4AYQ

Hi phill

I have shunts in circuit now for analogue meters, can I connect the logger across them with the meter, they are 75mv shunts.

All the best

Bob

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norcold
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Posted: 29 December 2011 at 2:48am | IP Logged Quote norcold

The designer of the SC logger goes into the importance of the accuracy of the ADC system ie the voltage regulation of the supply voltage to the sensors. He quotes the microcontroller can have voltage reference errors as high as +/- 5% which when multiplied by the sensors possible errors and lineararity can make its readings meaningless, thus the need I feel to calibrate and adjust each individual sensor through the script or program and checking with a known accurate meter.
I have played a lot around in this area taking into consideration my lack of knowledge re electronics and believe once I have the inverters logging running alongside with its shunts and can compare both against my two factory meters (fluke & mastech) I`ll get an idea of their accuracy. Although I do recall from my days of repairs to the curing systems in tobacco barns, even mercury thermometers(wet & dry) never totally agree with each other and believe that will probably prove to be more so in this case. But am keeping an open mind and learning I think!

PS The fluke and mastech do not agree with each other exactly but are in the same ballpark.

Edited by norcold on 29 December 2011 at 2:52am


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sjh7132
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Posted: 29 December 2011 at 3:00am | IP Logged Quote sjh7132

VK4AYQ wrote:
Hi phill

I have shunts in circuit now for analogue meters, can I connect the logger across them with the meter, they are 75mv shunts.

All the best

Bob


If one of the ends of your shut is at ground potential you could probably connect a logger. If the shunt is up at some higher voltage, the meters wouldn't care, but your logger probably would.

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Posted: 29 December 2011 at 9:16am | IP Logged Quote Warpspeed



The LEM series of current transducers offer much better performance for around $30.00

http://www.datasheetcatalog.com/datasheets_pdf/L/A/5/5/LA55P .shtml

These also use a Hall effect device, but they are a very clever high gain current servo system, not just a simple bare Hall effect sensor.
It overcomes most of the problems of Hall effect current sensing by placing the sensor inside a closed very high gain feedback loop.

The result is an 0 to 50 Amp measurement range, will measure dc or ac to 200 Khz, zero current output measurement error is in the very low milliamp range, very impressive for a 50 Amp sensor.
Linearity is also exceptionally good, because of the very high gain of the internal current servo system, and output noise is also extremely low.

By passing more than one turn through the rectangular central hole, you can multiply the current measurement sensitivity.
One turn = 50A range, two turns = 25 A range, ten turns = 5 Amp range and so on.

There is also a 100 Amp version as shown in the above picture.

Only real disadvantage is they require both a positive and a negative supply voltage. But a very simple low power voltage pump circuit would easily provide a negative supply rail if you only have a positive supply voltage available.

Edited by Warpspeed on 29 December 2011 at 9:30am


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