Current sensors and monitoring energies

Hi everyone!

After some searches - unfortunately without answer - here I am, asking you some questions :)

I have a project which consists in giving me the consumption and production in real time for several energies (wind and photovoltaic, actually). In order to do this, I use several current sensors connected to an Arduino Uno rev3 (used as a A/D converter), which will be linked to a Raspberry PI and a LCD Screen (with Domoticz installed on this, to have an user-friendly interface).

Anyway, here are my questions :

Let's imagine that the solar panel produces a current of 20 amperes. We would have an analog current of 6.66 milliamperes from the current probe, knowing that the Arduino accepts a tension between 0 and 5 Volts... According to the ohm's law (V x A = W), with a 10 ohm resistance for example, we will have 0,0666*10=0,666V Is that sufficient, or is an operational amplifier necessary?

My current sensors are the following ones : http://shop.openenergymonitor.com/100a-max-clip-on-current-sensor-ct/ and http://www.econologie.com/shop/ecowatt-pinces-amperemetriques-pour-triphase-p-320.html?zenid=84669184cc352653e3618b468378ac89 (without the conversion) Where could we find the missing specifications for these current sensors?

Does the Arduino convert directly the datas collected (analog) if I connect the Raspberry PI on the Arduino's digital outputs ? In fact, how could I connect them together?

Thanks a lot by advance,

Does the Arduino convert directly the datas collected (analog) if I connect the Raspberry PI on the Arduino's digital outputs ? In fact, how could I connect them together?

Before going deeper . . . .how do you plan to connect the arduino to the raspberry? (I mean, which pins and/or ports . . .?)

Regards

vffgaston: Before going deeper . . . .how do you plan to connect the arduino to the raspberry? (I mean, which pins and/or ports . . .?)

Regards

Hello,

Thanks for your answer. That's exactly my question : how to connect them together. Of course there is the USB port - with an external supply because the Raspberry will probably not support everything -but maybe there are other ways.

What would you recommend ?

Regards

That's exactly my question : how to connect them together.

OK. Sorry for the delay.

There are some other forers that do know, by far, much more than I do on this (and many other) concern(s); anyway, I'll give some (no dangerous) advice:

1) I will assume that the rapsberry is like a conventional PC (I do not know linux) so I have to make some assumptions: USB works the same; you can use keyboard and screen, etcetera

2) It's crucial to know what the speed of data in beetwen arduino and rapsberry is neccesary. I'm not speaking of baud rate and/or clock frequencies and things like that, but on the number of readouts from your sensors (after being processed by the arduino) you need to send to the rapsberry.

3) if it is not enormous (say, more than 10.000 by second) the best is to use a common -communications- solution; I would say USB. This means you need software in both sides to accomplish that, but sure you can find lots of libraries for rapsberry to do that (in arduino you have them). There are too concerns on the distance in beetwen the two systems; if it is big (say over 10 - 20 m) perhaps you need a RS232; don't worry: there are small boards that convert from one protocol (USB) to the other (RS232) so you can start using the easy one (USB) and then upgrade it if necessary.

4) Using arduino as a ADC is an option. In fact, everytime the arduino reads an analog input is acting as a ADC, as far as it gives you the reading as a number you can operate (mathematically and many other senses -storing, displaying, . . .- speaking) with. You have to decide the resolution you want/need: the more the accuracy the slower the arduino will operate. For hobby purposes I'd say 10 bits (1024 different readouts -steps) is more than enough. Be carefull about this: i'd advice to choose a low resolution (few bits) to start with the project.

5) According to the precedent paragraph, unless you need something extraordinary, the very same software (libraries, your own skecthes) you would use in the arduino to, say, display the values, will do to prepare them to send them to the rapsberry, whatever the format (text, number) you choose to handle they will be "sendable" via USB: you only need the rapsberry to use the same format.

Hope it helps.

Regards

1/ Yep, no problem with a raspberry.

2/ I need 1 or 2 values per second (for 3 or 4 sensors, so 3-4x), no more. According to what you said, I'm far from being limited by USB, altough I don't know exactly the refresh rate of the current sensors.

3/ So yes, USB should do the job :). Speaking of distance, it won't be a problem because the Arduino will work really close to the system (sensors, raspberry etc...)

4/ Yep it shouldn't be a problem to reduce precision by choosing a low resolution, I guess. Are they customizable in Arduino IDE ? In fact, since I'm still stuck with the connecting part (linking current sensors to the Arduino is my real issue here because I don't know the connectics)

5/ I guess that the data will be transmitted from the Arduino to the Raspberry as a database (text or someting else), but as I said previously, the connection is the real problem. I guess when the sensors will be set up to the Arduino, It should be fine (well, i don't know yet but I hope so ^^). Anyway, when I'll have a someting readable (tension or current) by the arduino, that should do it.

Regards.

Let Arduino Yun Measure/Datalog DCV/ACV/DCA/ACA/R/CAP/Freq/Temperature

Thanks Sonnyyu.

Anybody has already connected a current sensor on Arduino?

Regards.