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Author Topic: How to connect current sensor to Arduino Uno?  (Read 1277 times)
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Hi,

I just bought a current sensor (http://shop.sumeetinstruments.com/index.php?route=product/product&product_id=495). I would like to connect the output of this current sensor to my Arduino Uno. However, the output from the current sensor is a jack that looks exactly like the jack for headphones. I know I need to measure the voltage being sent out across this pin but I have no idea how to connect this jack to the analog input pin of the arduino board.

Any advice must suggested. Was not able to find anything on Google about this.

Thanks
-sid
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Quote
I know I need to measure the voltage

Without a datasheet, it is practically useless.
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Yes, not enough information supplied in that product description to know everything required to wire to an arduino. This much is clear from the description, it's a straight AC only CT (current transformer) that requires a fixed resistor across the it's output connections to develop a AC voltage proportional to the AC current flowing in the primary of the CT. The size of the resistor is unknown because they fail to give the turns ratio of the CT. Once the resistor size is calculated correctly and installed, then you need to rectify and filter the AC and possible scale the voltage so that AC current range is converted to DC voltage range of no more then 0-5vdc to represent 0 to max amps of the primary current flow. So find a real datasheet before proceeding. Operating the CT with out a output load resistor on the CT output pins can destroy the CT and subject you to very high voltages due to the normal very high turns ratio that CTs use.

Lefty
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Right Here!
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The good news is that it is possible to resolve the issue.
The bad news is that it will take a lot of time and effort.

How much the unit cost, and how much time you're prepared to spend on it will be for you to decide.
You will need a reasonable test meter, and know how to calculate current in a resistor, given the voltage.

In the first place you need to be able to generate known AC currents, and the easiest way to do this is with a low voltage transformer and some chunky resistors.

Start with, say, 1amp, and put something like 1kohm across the sensor's terminals. Close the core on the current carrying wire and see what you get. You want to end up with about 10V at the maximum current you expect to measure.

This was the easy bit.

The hard part is converting that AC voltage to a DC signal in the range 0-5V. A conventional bridge rectifier is of limited use as it will lose 1.2V straight away and give you all sorts of linearity issues. It is possible to make zero offset rectifiers with Op-Amps, but the easiest method is to use dedicated RMS-DC chips which aren't too expensive. They are also very accurate.
« Last Edit: December 15, 2012, 06:33:21 pm by Folderol » Logged

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Take one step back and get yourself a hall sensor with a 0-5volt output.  Linearity problems solved - also monitors DC current in either direction.
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