RS485 converters

To communicate with a RS485 solar inverter, WebSolarLog needs a RS485<>USB converter. Almost every RS485 converter is compatible, and you can find cheap ones at DealExtreme.com or Ebay.com.

We tested a couple of RS485 converters on the RaspberryPi. Based on these tests, we advise to buy a converter with an PL2303 or CH340T chipset.

Currently we run multiple test RaspberryPi’s with PL2303 or CH340T chipsets on SMA, and PowerOne solar inverters.

If you have any questions, suggestions or what so ever regarding this post, feel free to post on our google support forum:
http://www.websolarlog.com/index.php/help-support/

RS485 protocol for (solar) inverters

The RS485 is a serial protocol for communication between digital devices. Solar inverter manufacturers often use this protocol let their inverters communicate with the outside world.

The RS485 protocol has, for (solar) inverters, a couple of advantages against RS232:

  • works over a big distance (till 1200 metres (4000 feet))
  • supports a maximum of 32 – 256 devices, which makes possible to communicate with a 32-256 inverters on a bus.

Source: http://en.wikipedia.org/wiki/RS-485

These are the 2 biggest advantages and make it possible to connect a big number of inverters on a bus and let them communicate over a big distance.

To let WebSolarLog gather data from the inverter, it needs a RS485<>USB converter. The converter makes it possible to read the data from the inverter.

If you have any questions, suggestions or what so ever regarding this post, feel free to post on our google support forum:
http://www.websolarlog.com/index.php/help-support/

Hardware specifications

The design of WebSolarLog makes it possible to run WebSolarLog on a low-costs and low-power device.

We recommend the following minimal specs:

  • processor: 800MHz
  • memory: 256MB
  • diskspace: 2GB

WebSolarLog is successfully tested on the following devices:

Energy consumption of the RaspberryPi:
The RaspberryPi is a very low powered ARM device and consumes around the 4 – 4,5W.
We did a endurance test of a couple of day with the following setup:

The RaspberryPi can be powered by a USB-port. So we connected the USB-HUB to the grid and connected the RaspberryPi to one of the USB-ports of the HUB. The WiFi-dongle and RS485 converter were connected to the HUB. This setup consumed 130W a day, what gives it a average of 5,4W a hour. This setup consumes a whopping 47kWh a year, for this you have a fully functional Webbased Solar Logger.

 

If you have any questions, suggestions or what so ever regarding this post, feel free to post on our google support forum:
http://www.websolarlog.com/index.php/help-support/