DIY wireless remote meter for the SS MPPT

_OS_ · March 2009

Hi everybody!

I have started working on a wireless, remote meter for my cabin system. The plan is to install the transmitter in the tool shed where my CC and batteries are and a receiver in the living room of my cabin (and also an optional USB dongle receiver that can be plugged into a laptop).

As wireless transmitter I will use the Nordic Semiconductor nRF24LE1 and receiver I will use the same (and for the USB dongle a nRF24LU1p).

The transmitter will read the battery voltage, panel voltage, charge current, battery temperature and ambient temperature via serial line from the SunSaver MPPT controller. The current in/out of the batteries will be calculated by measuring the voltage over the Trimetric shunt.

I have e-mailed Morningstar and the author of SC-View for any source code they might have for the Modbus protocol on the SS MPPT but both replies where negative. So I have spent the last week writing a MPPT modbus "emulator" that I can use to debug the firmware. I now have the emulator up and running in my study interfacing SC-View. The reason I did this is because my SS MPPT is in use in my cabin system way up in the snowy mountains and I am developing the wireless meter in my study at home.

I will get back with more photos and information later. I will put source code, any drawings and so on on the web.

Below is a picture of two nRFgo evaluation boards with nRF24Le1 modules inserted. I will use these evaluation boards to develop and debug the firmware and move the nRF modules to a custom made PCB when done.

Please notify me if this post is inappropriate for this forum.

BB. · March 2009

Re: DIY wireless remote meter for the SS MPPT

Looks like a very interesting project...

My only caveat: What will be the power consumption of the transmitter/receiver/logging equipment.

This can be a significant drain on small systems.

-Bill

_OS_ · March 2009

Re: DIY wireless remote meter for the SS MPPT

BB. wrote: »

Looks like a very interesting project...

My only caveat: What will be the power consumption of the transmitter/receiver/logging equipment.

This can be a significant drain on small systems.

-Bill

My goal is to keep the average current consumption on the logger/transmitter below 5mA. I plan to sample all the variables mentioned above every second and the system will go to sleep in between. In sleep the nRF chip only consumes a few microamps. Compared to the 35mA around the clock drawing in the SS MPPT and 16mA for the Trimetric it is almost neglible.

My main concern is the range of the wireless since these chips are targeted at wireless PC accessories. There is also a module with an SMA connector for an external antenna I can use in case the range is not good enough with the PCB antennas in the picture above.

I also plan to install a device that disconnects the MPPT from my system at night since I am not using the 12V output on the unit and there is therefore zero current in and out. There is only the 35mA current consumed by the unit itself. I guess the Morningstar engineers have not considered a system where an inverter is used and no current drawn from the 12V outputs. Such a system can go to deep power down at night since there is no current to measure.

I have started a blog and will post updates there:
http://osaether.wordpress.com/

OS

mike95490 · March 2009

Re: DIY wireless remote meter for the SS MPPT

Way cool. Thanks for the info.

Had you looked into ZigBee radios ? Longer range, same band I believe, but lower data rate

_OS_ · March 2009

Re: DIY wireless remote meter for the SS MPPT

mike90045 wrote: »

Way cool. Thanks for the info.

Had you looked into ZigBee radios ? Longer range, same band I believe, but lower data rate

No, I haven't looked at ZigBee because I know the nRF chips very well.

OS

K4GAA · March 2009

Re: DIY wireless remote meter for the SS MPPT

_OS_ wrote: »

My main concern is the range of the wireless since these chips are targeted at wireless PC accessories. There is also a module with an SMA connector for an external antenna I can use in case the range is not good enough with the PCB antennas in the picture above. OS

I'm interested in your project because I have a SS MPPT solar charge controller and a Trimetric meter in my RV. I was considering the use the Aircable RS232 to USB Bluetooth devices. They have a variety of options to extend the range.

https://www.aircable.net/

I've been using a laptop to monitor performance locally but it would be nice to remotely see how the solar/batteries are doing when the RV is idle for the winter. I only need about 150 foot range. I've been using both Solar Guppy's software as well as Morningstar's for local monitoring the charge controller.

I'll look forward to tracking your progress on your blog. Ray

_OS_ · March 2009

Re: DIY wireless remote meter for the SS MPPT

I have a test version of my remote meter up and running now and checked it in my system yesterday. I noticed that the SS MPPT reported a load current of 0.07A (sometimes 0.17A) even when the load was disconnected. I first thought this was an error in my firmware but the MSView software showed the same current. I e-mailed Morningstar and got this reply:

It is a minor current offset that the controller is not accounting for. I have tested, verified, and noted this on a new unit here. The offset will be adjusted to account for this in the next firmware update.

I have not updated my blog lately but will soon and include a link to the source code.

Ole

DIY wireless remote meter for the SS MPPT

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