Yousif
Posts: 14
Joined: Fri Mar 11, 2016 7:23 pm

voltage and current sensors

Mon Apr 11, 2016 6:57 pm

Hello everyone
I am working on a solar panel i-v tracer project using the raspberry pi and the raspberry pi touch screen.
I am looking for voltage and current sensors that work with the raspberry pi and can give me accurate readings.

Thanks

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mikronauts
Posts: 2716
Joined: Sat Jan 05, 2013 7:28 pm
Contact: Website

Re: voltage and current sensors

Mon Apr 11, 2016 7:21 pm

See my article:

http://www.mikronauts.com/raspberry-pi/ ... and-howto/

You can get ACS712 modules to measure current.
Yousif wrote:Hello everyone
I am working on a solar panel i-v tracer project using the raspberry pi and the raspberry pi touch screen.
I am looking for voltage and current sensors that work with the raspberry pi and can give me accurate readings.

Thanks
http://Mikronauts.com - home of EZasPi, RoboPi, Pi Rtc Dio and Pi Jumper @Mikronauts on Twitter
Advanced Robotics, I/O expansion and prototyping boards for the Raspberry Pi

Yousif
Posts: 14
Joined: Fri Mar 11, 2016 7:23 pm

Re: voltage and current sensors

Mon Apr 11, 2016 7:27 pm

How is the accuracy of the ACS712 sensor with measuring currents because i am measuring really small currents (0-0.5)A???
will it work well for these small currents???

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adun
Posts: 102
Joined: Fri Mar 20, 2015 9:25 am
Location: Switzerland

Re: voltage and current sensors

Mon Apr 11, 2016 7:32 pm

I suggest you use a mcp3422 adc that will be attached to the Pi's i2c bus.
there is a good reference design in the datasheet for using mcp3422 as a battery gauge.
Basically you use a voltage divider to get the voltage and measure the voltage drop over a very small resistor where you can calculate the current from

Image

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davidcoton
Posts: 4008
Joined: Mon Sep 01, 2014 2:37 pm
Location: Cambridge, UK

Re: voltage and current sensors

Mon Apr 11, 2016 9:23 pm

What is the voltage and current range that you need, and what resolution? Do you need AC measurements as well as DC?

If you are working with mains connected systems, you must be familiar with the wiring regulations in your country, and with safe practices at the voltages concerned. You must make sure that the sensors you use are appropriate and safe. If you do not have the necessary knowledge and experience, do not attempt any direct connections to mains voltages. Solar panel voltages can be as high or higher than mains -- that is 300V or more. Mistakes can damage your Pi, your property (by causing fire), or your life.
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Yousif
Posts: 14
Joined: Fri Mar 11, 2016 7:23 pm

Re: voltage and current sensors

Tue Apr 12, 2016 3:14 pm

I am using a small solar panel (0-3)V range and current in range(0-0.5)amps so i don't think there is any safety problems

csatt
Posts: 6
Joined: Sat Oct 25, 2014 12:07 am

Re: voltage and current sensors

Wed Apr 20, 2016 11:17 pm

Hi Yousif,

I built an IV curve tracer and posted the design on GitHub:

https://github.com/csatt/IV_Swinger

The documentation describes how I implemented the ammeter and voltmeter. I used the ADS1115 ADC and a 10A/75mV (7.5mΩ) shunt resistor. I tried the ACS712 for the ammeter. But my design uses relays which generate magnetic fields that interfere with the Hall effect (which is how the ACS712 measures current). You are dealing with a smaller range of voltages and current than I was, but my ammeter and voltmeter are very accurate even at the low ends, so I think a similar design will work for you.

- Chris

Yousif
Posts: 14
Joined: Fri Mar 11, 2016 7:23 pm

Re: voltage and current sensors

Thu Apr 21, 2016 5:14 pm

Thank you Chris

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