mr3k
Posts: 1
Joined: Wed Feb 25, 2015 11:30 am

Current sensing

Wed Feb 25, 2015 11:32 am

Hello,

We are doing a school project where we want to measure current from a power cord (230V). We found this sensor: “Non-Invasive Current Sensor - 30A” (https://www.sparkfun.com/products/11005). How can we connect this to our Raspberry PI?

Thanks in advance.

texy
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Re: Current sensing

Wed Feb 25, 2015 12:46 pm

Hi and welcome to the forum.
From the webpage you supplied, it pointed to an arduino project that you can use as a starting point :
http://openenergymonitor.org/emon/node/58

However this relies on the fact that the arduino has analogue inputs, which the Pi doesn't have. You will need to hook up an
ADC chip to the pi, to convert the analogue voltage across the load resistor to a digital form.
So you have some homework to do........
Texy
Various male/female 40- and 26-way GPIO header for sale here ( IDEAL FOR YOUR PiZero ):
https://www.raspberrypi.org/forums/viewtopic.php?f=93&t=147682#p971555

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Tage
Posts: 287
Joined: Fri May 24, 2013 2:29 am
Location: St Thomas, Ontario Canada

Re: Current sensing

Wed Feb 25, 2015 3:57 pm

http://www.mouser.com/ProductDetail/Tri ... cs/CSE186L
here is a cheaper current transformer rated for 10A. but you need to do some soldering as the core cannot be separated to insert the ac wire.
with all current transformers it is important that the correct resistor is connected to the sense output (secondary winding) before you run any current in the ac power wire. if you forget to connect a resistor to the winding the voltage can become quite high and the current transformer isolation is damaged.

grahamed
Posts: 277
Joined: Mon Jan 30, 2012 7:01 pm

Re: Current sensing

Wed Feb 25, 2015 10:37 pm

Hi

One thing to note, all current transformers have a maximum rating obviously. Less obviously they have a minimum rating - below maybe 5% of rating they may produce little or no output due to hysteresis in the core. So choose your rating with care.

Also take notice of the need for termination as mentioned DO NOT USE TERMINATED - if there is no circuit the voltage will rise until it finds a way, probably by breaking down the insulation of the transformer. Or it may spark a little.

You do understand that you must pass only one conductor not the whole cable through the transformer?

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