Arduino system with serial port and wireless internet access

Projects General Guidance
1

I'm interested in doing an Arduino project to:-

a) Read data via a serial port from my Solar PV system inverter
b) Reformat the data
c) Send the data to a website (PVOutput.org) via a wireless connection to my router

Could somebody please advise me what a suitable combination of basic Arduino board and shields
would provide the necessary hardware to do this?

I'm currently using a dedicated ASUS eeePC to achieve this function, but I'd like to develop an Arduino solution
to replace the netbook, both as a learning exercise, and to achieve a more reliable and cost effective alternative.

Than you.

2

Sounds like the combination of a basic Arduino UNO and a WiFi shield would do what you want.

3

Thank you.
Can I get an RS232 cable which connects to pins on the Uno board and has an RS232 connector on the other end?
I've ordered some learning documentation on the Arduino but haven't actually seen one yet.

4

hi gmj3191,

I don't think that you can just connect an rs232 cable to the arduino directly, you need a chip to convert the rs232 to the correct logic type,
Read through this, It may help a little bit...

PhayilBoy

5

I see, thank you.
I had hoped one of the Arduino boards may have onboard RS232 hardware.

6

I believe you need to buy an RS232 to USB converter cable. They cost $1 USD from China on eBay.

As for sending the data to the internet, I would recommend some form of Arduino Ethernet. The easiest way is to just buy some kind of Wi-Fi shield and hope it works. This is easiest but most expensive. The way I would do it is to buy a pair of Nordic n so that your data goes from Arduino > Nordic link > Arduino with ethernet. You can buy the official ethernet shield or cheap ethernet modules such as the ENC28J60 since they have recently come out with libraries that enable DHCP and examples to send data to Pachube. (GitHub - njh/EtherCard: EtherCard is an IPv4 driver for the ENC28J60 chip, compatible with Arduino IDE) This way if you want multiple data loggers, you only have to buy more Nordics rather than more Wi-Fi shields.

7

Thanks, but I don't really want to do that as two ENC28J60 boards would cost $70 and I don't want to run an Ethernet cable.
I just want to replace my existing wireless system based on an eeePC with a custom Arduino solution.
I don't need Pachube as there is an existing system at PVOutput.org with a standard data entry method.

What I want to do is is

Inverter Arduino <Router - Internet> - PVOutput.org

8

... also,would using the USB port for the RS232 interfacing complicate testing, as I thought that the USB port will be used to connect to the IDE, but I haven't got my head around that yet as I've only just started looking at Arduino development issues.

9

Does your inverter have a Female or Male DB9 connector for serial?

Looks like for $3.58 you get a DB9F-RS232 to TTL Serial converter and a USB power cable to provide it with power:
http://www.ebay.com/itm/RS232-To-TTL-Converter-Module-Built-in-MAX232CPE-Transfer-Chip-With-4PCS-Cables-/270845851440?pt=LH_DefaultDomain_0&hash=item3f0fabb730#ht_3506wt_1107
Assuming your inverter doesn't have a USB port you will probably have to provide 5V power from the Arduino.

An alternative, for $19.95, is a DB9M-RS232 to TTL Serial adapter cable:
http://www.ebay.com/itm/MAX232-RS232-to-TTL-serial-cable-in-DB9-shell-Monitor-ECS-embedded-uC-OpenWRT-/290613252159?pt=LH_DefaultDomain_0&hash=item43a9e6503f#ht_1914wt_1107
It fits a six-pin header like the classic FTDI (USB to Serial) cable.

10

The "Inverter Arduino" part probably be done with an NPN transistor and two resistors. Below link is to some rs232 to ttl alternatives. Bottom is how I inverted rs232 to ttl for a chip using the two resistors and an NPN transistor.