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.

Building an Industrial Robot - Part 1 - The Robot Brain and Body

Here's my project to make a universal platform for industrial robot experiments.

The requirements are to develop and construct an industrial grade tracked robot for under US$2000.

The robot has to be able to work in harsh environments, be net-workable and operate for long periods before recharging.


A series of blogs will follow the progress of the tracked robot project, and this part is focused on the base construction and layout of the robot's computer.


The Robot's Main Body

Before you mount a computer brains for a robot, you need a body to mount it, so I created a quick, cheap and strong assembly method.

Side of the robot without the hatch

Top of the robot without the hatch

The main body is made of poly carbonate panels with aluminium framing for lightness and strength.

The panels are glued to the aluminium frame with silicon, the same way you would build a fishtank.

This makes construction of a robot body easy, without too much drilling and reducing the number of bolts or rivets that might come lose during the robot's operation.

Also, construction makes the robot's main body water-proof, in case it has to operate in low level water.

The main body has been sprayed with a grey primer and matt black finishing paint to protect the polycarbonate body and increase water-proofing.

It also gives stealth or a black ops look to the robot.

Side view with the hatch on

Top view with the hatch on

With the top hatch and soft mounts on, the main body is sealed for protection of the robot's computer systems.

The GPS is mounted on the top, next to the 2.4 GHz omnidirectional antenna.

The pole mount at the other end of the main body is for the web cam.

In the centre, the main hatch opens to access the computer system for system reprogramming, battery maintenance and internal repairs.


The Robot's Computer

The main brain of the robot will be driven by a Mini-ITX system running Linux. The Mini-ITX system will be using a SSD to boot  and run, which removes the requirement for a hard drive that might be damaged when the robot is in motion. The idea behind the Mini-ITX is to reduce complexity from hardware into software tasks, and making the programming and design of the robot's brains much easier.

The main part of the robot lies in the PIC Micro-controller connected to the Mini-ITX by a RS232  connection.

This controller has 20 inputs and outputs for driving motors and reading sensors.

The PIC Micro-controller allows the software on the Mini-ITX to interface with the robot's outside world.

The 802.11g Linksys bridge is set to connect to the local access point for remote access to the robot via IP, either for the information of a remote user or for the robot to download new information and instructions. The network security is done by WAP encryption on the layer 2 as well as 256 AES VPNs from the Linux OS.

The Webcam and GPS are plugged straight into the Mini-ITX via USB cables.

This supplies the robot's computer with GPS positioning and a digital eye for navigation.

Computer Layout Components: Mini-ITX computer 802.11g Ethernet Bridge USB GPS USB Webcam 2.4 GHz Antenna Pic Micro-controller Board USB, RS232, Cat5 and Coax cabling

The Robot Computer Layout

The above diagram show the logic layout of the connections and hardware used for the computer controller.

The Mini-ITX connections use Cat5 to the 802.11 bridge, RS232 to the PIC Micro-controller and USB to the web cam and the GPS.

The 802.11 bridge is also connected to an antenna with shielded coaxial cable.

The choice of operating system for this robot project is Gentoo Linux. I have found this Linux distribution ideal for embedded and custom designed systems. It is very easy to make live images and small OS footprints with Gentoo Linux. I have tested Gentoo Linux on Mini-ITX systems before without any issues.

More to come in the next parts of this project, as we examine the power system, track design, motor systems and software applications required.

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..