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Permalink Reply by Nick Arsov on May 28, 2012 at 10:19am

Hi Jibabio,

The simplest way up to 200A unidirectional or bidirectional for you is to use one of the Allegro's ICs ACS75x - http://www.allegromicro.com/Products/Current-Sensor-ICs/Fifty-To-Tw... .

For higher currents, it's better to use current divider technique - http://www.allegromicro.com/Design-Center/Technical-Documents/Hall-... . In this approach, you sense 1/2...1/5....1/10 of the real current for example where the main current flows through the high current schunt part, while the measurement is made in the measurement part ( the schunt has 2 sections ). Then you have to recalculate the real current.

Also for higher currents you can use a current sensing transformer. The problem with them is that they are not as slim as ICs.

If you decide to use another approach - schunt current sensing - high current schunt with a simple and cheap IC as a current monitor, you can use Diodes current monitors - http://diodes.com/products/catalog/list.php?parent-id=79 with a high current schunts from Isabellenhutte for example - http://www.isabellenhuette.de/en/products/ .

There's another approach of using N current monitors with current or voltage outputs and then make a SUM of them with an OpAmp.

If you have any questions, please just ask me.

Best regards

Nick

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Permalink Reply by jbabio on May 28, 2012 at 4:56pm

Thank you for your answer, Actually I have two 180A attopilot sensors and wish to use them. I will try arrange them in parallel and then add their outputs like in one of the examples from your links.

This way the current will be splitted between both sensors and as a result each sensor will only handle 116Amp at maximum load.

Thank you.

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Permalink Reply by Nick Arsov on May 28, 2012 at 10:14pm

Hi jbabio,

I'd suggest using another approach. At such high currents you should be very very carefull as I'd seen glowing cables!!!

I suggest dividing the current flow to two circuits -> 4 + 4. The current flow do not disturb current reading. Then you can sum the current readings but note that if the full scale of the 180A current sensor is 5V(3.3V), you can't simply sum them. The easiest way is first attenuate each output to 1/2, then sum the two outputs. Thus you'll have 100% full scale at 360A. Also you can first sum them and then attenuate the signal to get within 5V(3.3V) scale. The second approach is much uncomfortable as you need a higher stabilized power supply for the summing OpAmp. Do look at the datasheet of your sensors for the full scale and then decide.

Best regards

Nick

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Permalink Reply by jbabio on June 4, 2012 at 7:44am

Finally I'm using H07V-K 25mm2 cable between batteries and two power distribution boards.

The power distribution system is arranged this way:

Each 100Amp power distribution board carries one polarity and both are bond with 0,5mm hex spacers, (soldered cables are in opposed sides) this way I have the exact space between outer faces of the boards (up and down) to solder XT60 connectors for the ESCs.

And here came the questions:

Could you specify the circuit needed to atenuate the and then add the signal of the two attopilot sensors? I could install them on the batteries (one on each battery) and since they are installed in parallel should each sensor handle and measure only half the total draw.

I'm also studying the option to use this more secure (but bigger) non invasive Hall Effect sensor Suggestions?

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Permalink Reply by Nick Arsov on June 4, 2012 at 8:20am

Hi Jbabio,

If you don't want to make an additional summing amplifier, have a look here - http://bg.farnell.com/jsp/search/browse.jsp?N=2003+203849+110129494...|0&Ntk=gensearch&Ntt=current+sensor&Ntx=mode+matchallpartial&locale=bg_BG&appliedparametrics=true&getResults=true&suppressRedirect=true&isRedirect=&originalQueryURL=/jsp/search/browse.jsp%3FN%3D2003%2B203849%26Ntk%3Dgensearch%26Ntt%3Dcurrent%2Bsensor%26Ntx%3Dmode%2Bmatchallpartial%26No%3D0%26getResults%3Dtrue%26appliedparametrics%3Dtrue%26locale%3Dbg_BG%26divisionLocale%3Dbg_BG%26catalogId%3D%26skipManufacturer%3Dfalse%26skipParametricAttributeId%3D%26prevNValues%3D2003%2B203849

You can find here your current sensor.

If you decide to use a summing OpAmp, then have a look here - http://www.ecircuitcenter.com/circuits/opsum/opsum.htm  or  here - https://www.google.bg/search?hl=bg&lr=&newwindow=1&q=op...

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Permalink Reply by Gabriel on December 10, 2012 at 10:30am

Hi ! Thanks for the links !

I would need to measure about 180-200A, I've got an APM 2.5 with its power module (90A max).

What would I need to do, where do I need to connect the sensor's output ?  Would it work like the original power module current sensor?

For example, with one of these current sensors :

http://bg.farnell.com/jsp/search/browse.jsp?N=2003+203849+110129494...

Thanks.

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Permalink Reply by Nick Arsov on December 10, 2012 at 11:27am

Hi Gabriel,

Here it is a good high current sensor - http://www.hitecrcd.com/products/aircraft-radios-receivers-and-acce...

You have to follow the APM documentation on where to connect the sensor - http://code.google.com/p/ardupilot-mega/wiki/APM25board

Best regards

Nick

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Permalink Reply by Gabriel on December 10, 2012 at 2:44pm

Great sensor ! just what I need ^^ Thank you Nick.

But do you think this sensor is compatible with APM ?
Do I Just need to connect it to port A2 ?

Thank you very much for your help, my problem is almost solved ^^"

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