Solar Grid Inverter Monitoring System - Part 2

The second part of this project requires the RS232 to be signalling at a longer distance than the usual fifteen metre limitations.

To overcome this distance limitation and maintain reliability of the serial network, we use of a special telecommunication device called a RS232 extender. 


The RS232 Extender

The Gefen RS232 extenders will be used to extend the RS232 connection from the Fronius IG grid inverters to the remote location, with over one hundred feet of Cat5e cable.

The Gefen RS232 extenders will perfectly reproduce all 9 pins from one end to the other and have the ability to provide power over Ethernet to the second extender, saving on extra cables and power supplies.

The extender units act as a sender and receiver pair on the RS232 network. Allowing the grid inverter's data logger to send Windows computer information to the Fronius access software.

The RS232 extender sender unit connects to Fronius IG grid inverter at one end and the RS232 extender receiver at the computer terminal at the other end.

Then the Cat5e cable connects the send and receive extender units, over 300 metres away. The sender unit is powered by a 5 volt power supply, which will also power the receiver via the Cat5e cable.


The Fronius IG Access Software

The free Fronius Solar access software is available for download from their corporate website at http://www.fronius.com. The software provides advanced onsite data analysis and archiving options for the PC. As an administrative tool, it offers full setup options for all system components in Solar Net.

The software is easy to install on the Windows system, with a helpful installer wizard.

Once installed, the software is located in the programs section of the windows start menu.

The Fronius access software splash screen displays the general energy output information for the photovoltaic solar power system.

Under the administration menu, the new PV system can be added and configured for the RS232 connection back to the grid inverter's data logger.

In the next part of this series, I will be looking at connecting the monitoring software and data logger to collect information from the school's solar power system, and explaining the features and advantages that computerised power monitoring can have for an organisation.


Other PV Solar Powered Systems and Concepts

A PV solar power system has many other applications apart from grid power installations. One example is NASA's Helios aircraft, remotely piloted to fly at high altitudes.

The electrically powered Helios is constructed mostly of composite materials such as carbon fibre, graphite epoxy, Kevlar, styrofoam, and a thin, transparent plastic skin.

The main tubular wing spar is made of carbon fibre. The spar, which is thicker on the top and bottom to absorb the constant bending motions that occur during flight, is also wrapped with Nomex and Kevlar for additional strength.

The wing ribs are made of epoxy and carbon fibre. Shaped styrofoam is used for the wing's leading edge and a durable clear plastic film covers the entire wing.

The Helios collects a variety of information in the atmosphere, and runs mainly on solar power.

On August 14, 2001, the Helios Prototype, piloted remotely by Greg Kendall, reached an altitude of 96,863 feet, a world record for sustained horizontal flight by a winged aircraft.

The altitude was more than 11,000 feet or more than 2 miles (3.2 km) above the previous record for sustained flight by a winged aircraft. In addition, the aircraft spent more than 40 minutes above 96,000 feet.

Tragically the Helios crashed over the Pacific Ocean on 26 June 2003.

Easy ESXi 4.1 with serial or USB UPS control

In the past, there has always been a problem with setting up USB uninterruptible power supply to VMware ESXi servers.  Here is the method of enabling a VMware ESXi 4.1 bare-metal server to communicate with an inexpensive serial or USB-only UPS system.

Install a Guest Windows System

You will need to install a Windows virtual machine to run the power management software, and connect to the UPS system.


I have used APC Powerchute software on a Windows 2008 server with this installation method, and encountered no problems.

Most Windows OS guests with USB management software should work in the same way.


Enabling the USB Pass-through  

Now that ESXi 4.1 has been released, it is possible to use a USB data cable on any UPS and communicate with Windows control software.  

ESXi 4.1 has the ability to make a USB connection from the server hardware, directly through to a virtual machine hosted on the same server.

This allows UPS monitoring software to run on a windows virtual machine on the server and talk to the UPS on the ESXi server USB hardware.

You will need to make sure the USB adapter is attached to only the power controller guest OS, to minimise other guest OS conflicts. 

The management and attachment of the USB hardware is done in the virtual machine hardware configuration screen.

When adding USB hardware to the hardware of the virtual machine, a new option is now available for direct USB hardware access.


Enabling the SSH Service for Root Access

The next step is to enable the SSH service on the ESXi server, so a root remote console is present via SSH.

You will need physical access to the ESXi server, so you can login to its console as the root user.

Edit the configuration file for SSH with the following command:

nano /etc/ssh/sshd_config

Find the line that starts with PermitRootLogin and change the "no" to "yes".
 
Restart the sshd service with the command:

service sshd restart

The SSH service will now accept root logins to the console for running scripts. 



Windows Guest Script File  

On the Windows virtual machine running the Powerchute software, a small .bat file needs to be created, pointing to a free SSH client called Putty.

You can download Putty from their website. http://www.chiark.greenend.org.uk/~sgtatham/putty/ 

After getting Putty and setting up the .bat script, log into the same directory on the Windows guest. 

You will be able to point your UPS control software directly to the shut-down script on the local host.

Windows .bat file:
-------------------------------------------------

putty "server-address" -l root -pw "password" -m Unix_Commands

-------------------------------------------------


Unix_Commands file:
-------------------------------------------------

poweroff

exit

-------------------------------------------------


Final Notes

This new feature for USB connections in ESXi 4.1 makes it very easy to implement UPS systems into the VMware environment. I have only tried this with Windows 2008, running APC Powerchute software and uninterruptible power supply with USB control. But I believe any configuration of Windows and power control software should work.

Solar Grid Inverter Monitoring System - Part 1

Solar based power has become an important part of modern strategy for some organisations as they move from carbon based fuel dependence to renewable energy. One of my current projects is looking at a solar power applications for a school that is working towards establishing a carbon neutral power system.

The solar panel array that is currently installed on the school's roof has enough panel area to produce up to 5 kilowatts of electrical power on a sunny day.


Fronius Grid Inverters
 

Three Fronius Grid Inverters

Three Fronius IG 30 grid inverters can feed up to 7.5 kilowatts of power back into the grid, or to the school's AC electrical systems. These high power inverters form the centre of the photovoltaic system, as AC power and access back to the power grid is essential at the school.

Grid inverters are essential for a power system to have mains AC power and photovoltaic power, enabling seamless use of both power sources as a single power source.


The goal of this project is to network the Fronius inverters into a PC system running MS Windows, so that information about the power grid and photovoltaic solar array can be collected for educational and organisational use.



Cabling the Grid Inverters for Computer Monitoring

Inverter, fuse box and Cat5 plate

Blue cables are the serial bus

The three Fronius grid inverters have been mounted on the wall in a way that makes it easy to network the units together.

The three inverter units all have special Com cards, so they can be networked together in a bus type network.

At each end of the Cat5 bus network, special terminator plugs are used to close circuit on the network.

Grid Inverter Bus Network and PC Serial Connection

The last unit has a special data logger card that gives the Fronius grid inverters a data IO port for a computer via RS232.

The data logger card has a DB9 connector, which has been then converted to Cat5 for easy of use in the networking cabinet. 

RJ45 connector in the rack to the Data Logger

The cable run from the DB9 connector on the inverter can be up to 20 metres in length. But for longer lengths of cable, RS232 extenders maybe required. For this example, the Cat5 serial cable is terminated into the network rack in another building.

The Windows PC is connected to the terminated rack connection, which connects back to the Fronius grid inverters with which the Windows PC will be communicating.



For part 2 of this project, I install and setup the Fronius IG access software on the Windows PC.

I will also be explaining the features and advantages that computerised power monitoring can have for an organisation.

Stay tuned.

Technical References Collection now Avaliable on Scribd

Burning the Midnight has added a new section to its Scribd profile, called Technical References. It contains many useful documents and wall sheets for wireless, electronics and network technologies. Handy to have hanging in the laboratory or workshop for a quick reference: http://www.scribd.com/burningthemidnight

Publications include:

• Motorola Canopy Reset Default Plug
• Radio Transmitter Power dBm to Watt Conversion Table
• IP Subnet Reference Sheet
• JEDEC Coding System Table for Diodes and Transistors
• Serial Console Cable Howto and Wiring Diagram
• Ami Bios Beep Codes Reference
• Optical Fibre Connector Reference Sheet
• Electronic Formulas
• Resistor Colour Value Howto and Code Sheet
• Ceramic and Mylar Capacitor Value Howto and Code Sheet

Check them out at http://www.scribd.com/burningthemidnight in the Technical References section of the Burning the Midnight profile. Also, the Technical Reviews section on Scribd has a lot of information on wireless, networking and security hardware systems. Well worth a look.

Redundant 48 Volt Power Supply - Part 2 - Wiring up the Rack and PSU

Now comes the all important job of wiring up the rack mounted power supply units.

This part of the project requires heaps of wire, a soldering iron, connectors and a steady hand.

Important WARNING - The next part is for informational and academic use only. This system uses dangerous and lethal voltages. Only qualified and experienced technicians should work on high voltage power supply systems.

Wire up all the internals with the appropriate cable types and colour coding. It is important to use the correct wire types and colours for the 240AVC and 48VDC circuits. All the wire ends were soldered onto connectors or terminals and all exposed connections covered in heat shrink tubing. Also, the yellow grounding cable to the rack casing was securely attached to the earthing connector on the case.

The PSU & rack all wired up

Below is a diagram showing the PSU wiring in the 2ru rack case. With 240VAC mains power coming into the PSU unit and the clean 48VDC power being delivered out of the unit. 

Parts list per PSU circuit:

1x 3700K Resistor 1x LED with mount 1x 240VAC fuse holder 1x IEC socket with mount

1x DC power socket with mount 1x Ceramic fast blow fuse 1x Switch (Suitable for 240VAC) Loads of wire for 240 volt and 48 volt Applications

Below are images of the front and back panels. On the front panel is mounted the power switch, red LED and DC power connector socket. On the back is the IEC power socket for the 240 volts AC cord connection and the fuse holder with a quick blow ceramic fuse.

Close-up of the front of the rack

Close-up of the back of the rack

Now the task remaining was to make up the DC power cables and test the PSU units before turning them on (I used my multimeter all the way though the building process, which is good practice).

Everything looked good and I was ready to test with mains power and a heavy load on the DC outputs.

DC Power Cables

Testing the PSU racks

Put the tops back on and plug them in.

Test the DC voltage and ensure everything is fine at 48.2 VDC. No leaks or other obvious problems.

All done, with two redundant 48 VDC power supplies ready to be shipped out. (I also had another technician check it over).

PSU all finished front view

PSU rack all finished back view

Stay tuned to Burning the Midnight for the next and final part of this project.

I will be mounting the rack unit and connecting up the redundant power supply to a Longreach X-Band wireless backhaul.

More fun and excitement.

Redundant 48 Volt Power Supply - Part 1 - Mounting and PSU

I have started construction of two redundant 48 VDC power supplies for use with large scale telecommunication equipment.

They will be powered by a 240VAC UPS with a diesel backup generator.

These two PSUs are for two X-Band Longreach Wireless backhauls (CarrierComm backhauls), which can transmit <300Mbps over 50km.

More about them later... 

First of all, I needed something to mount everything into. Preferably a 2RU rack mounting. Found the rack kits at Jaycar Online. Jaycar is a handy place with loads of equipment and parts, and I wish they paid me for this ad.

Rack Mounting from Jaycar

Rack and Rack Mounting Kit

Next I needed to find some power supplies to fit the rack units. I shopped around online and picked up two TDK-Lambda HWS15-150-48A caged PSUs from Digikey.

These units are quiet, cool and slim, while still producing 3.3 amps at 48 volts.

Top View of the hws15-150

Front View of the hws15-150

The kits was easy to build, with easy installable din rails. The front and back panels are simple to remove and replace for case work. Mounting PSUs was also straight forward, with a few small screw holes to mount the fames at the bottom.

Rack with the PSUs mounted

Close-up of the rack mounted PSU

Removed the front and back panels to work on in the lab.

I had to cut and drill some mount holes into the panels for the IEC power mounts, LEDs, fuses and switches.

Sparks and aluminium bits flew everywhere. The front 3mm aluminium panel was a challenge to work with.

After preparing the panels, I then gave them a fresh coat of black paint to remove any of the scratches. 24 hours later, the dry panels are ready for components to be mounted. Then I assembled the main rack case.

Finished Panels

Look on Burning the Midnight for the next part of this project.

I will be wiring up the rack mount and PSUs and publishing the wiring diagrams, pictures and comments as the unit comes together.

News Flash!
"Part 2 - Wiring up the Rack and PSU" on up and online, so check the next chapter..

Latest Projects and Upcoming Articles

Here's some of the new projects that I have been working on. A bit of a mixed bag at the moment, from PSUs and robotics to VMware.

The projects include: VMWare Infrastructure review and tricks. Redundant 48 volts power supply for telecoms equipment. Solar system reporting to computer intergration software. A tracked robot running on Linux and wireless networking.

Stay turned for these informative and useful project updates.

Further project information will be added to the new Burning the Midnight website.

Check it out at http://sites.google.com/site/burningthemidnightproject/