Hi Guys,

Currently working on my own mppt project and i need to measure the output power from the solar panel. Im using a PIC MCU to measure the voltage and current.

Measuring the voltage is easy just a voltage divider connected to ADC input, however how can i measure the current coming out of the solar panel? I know i can use a low OHM resistor and amplify it with an opamp, but it get a bit complicated because i need a +/- 5volt power rail to supply the opamp, and also is this method accurate?

So.. for thos of you that have measured current before, how did you do it? what problems did you encounter? and what is the best way to go about doing it?

Thanks
Rock.

Another popular way of measuring current is via the use of a hall effect sensor, depending on how low the current is that you would like to measure depends on how many loops through a ferrite core you would need to do. I know you can buy ferrite cores with a notch cut in them ready for the hall effect sensor I have seen them on digikey and the like.


I know they have a variety of IC's out there that are capable of current measurement using hall effect sensors as well.

http://www.gmw.com/magnetic_sensors/sen ... CSA-1.html

this one looks pretty good if you are into making your own boards and such.

Hall effect sensors are very good, although the precision isn't as good as the standard op amp method.
Ive ordered some LT6106 samples from the linear technology, ill be experimenting with them as soon as they come in.

Here is LTs take on low side current sensing. For our applications the accuracy achieved by the first circuit is enough.



The output of the current amplifier goes to the ADC, and you can adjust the gain of the amp to suit your voltage reference.

For those of you after a good ADC for you micro controllers, I've successfully used the LTC1400. Its a serial SPI ADC with 12bit resolution at 400KSps.

Hi,

This is a very simple current sensor that I have designed for sensing currents on a ground-referenced line. It simply operates on the basis of a current mirror and a shunt resistor, and provides a good accuracy. Putting a small capacitor in parallel to R11 will reduce noise on the output.

Note however, that the output is inverted (zero current gives high output) and biased to the supply. A stable supply voltage is necessary.

Bouke

Hi Borke

Ive never that particular circuit before.. How does it fair with component tolerances??