Investigated inverter's panel meter communications

Found that all 8 wires (4 twisted pairs) had a signal.

And just probing with an ungrounded probe showed that these were 120v peak-to-peak:

Confirmed by switched to a 10x probe:

So my conclusion is that:
1) They are using a differential carrier on all 4 twisted pairs
2) I need to use a comparator to get a digital signal
3) My readings will be distorted by 50Hz 230v mains hum.
4) The timebase was  2 mSec/Div so period was 12 mSec / 80Hz

Interestingly the meter is packed with electronics:

And the 20A charge controller uses the base as a metal heatsink:

I'm hoping I may be able to upgrade a 10A controller to a 20A one myself but it doesn't look that straightforward.

2nd panel produces 7.2 A

Wired up second solar panel to a charge controller and 24V batteries.

Interestingly, this charge controller is rated at 20A (rather than 10A). Could this be why it reached 7.2A compared with 5.2A the first panel achieved yesterday through the 10A charge controller?

I must investigate before I buy the remaining three charge controllers.

Panel supplying 5.2A@36V (187W) and went off grid

Went off grid using 600W 24V pure sine wave inverter.

It can supply the extension (except for electric shower, washing machine and dryer).

And the main house (except cooker, kettle and fridge).

So I had it supplying lights, TV, satellite receiver, broadband router, etc for 2.5 hours (from 10 pm) from a 40 Ah 12v car battery and 90 Ah 12V leisure battery in series.

It was also supplying the extension from 12 noon to 8 pm.

It turns its fan on when it heats up. All worked better than expected.

Wired up Rasp Pi to monitor charge controller meter

I'm going to use the Raspberry Pi to replace the charge controller meter. (I can then monitor 5 charge controllers at once an dpost the result son the web).

But first I need to find out how the communications takes place over the RJ45 cable.

So I will monitor it with the Rasp Pi

The pin-out for the GPIO header and for the RJ45 I found on the web

I believe the Rasp Pi uses 3v3 voltage levels so I will need to buffer its inputs and if the RJ45 is using current mode rather than a voltage swing I may need to get a bit more crafty.

I'm also assuming a asynchronous protocol say 1 start, 8 data and 1 stop bit at 19K2 baud. But if they transfer in encrypted blocks it will be harder to decode.

Tried #3 235W panel with 2x 12v car batteries

Checked O/C voltage of panels #1 and #2 in the attic. Both still say 0v. #3 and #4 panels say 36v as expected. #5 I can't get to easily.

It was too windy and rainy to check the cabling for #1 and #2 on the roof so I connected #3 to the 12v/24v charge controller and meter and took two 12v car batteries out of my defunct Vitarras as a load.

Everything worked OK but the sun was too low (at 6 pm) to register above 0.0 A on the meter.

Also, one battery was down to 6v while the other was at 12v. So next I will use the 60W 12v system to charge this one back to 12v so the loads are more even.

Wired up my dual charge controller to 60W and 235W panels

Wired up my 12/24v dual charge controller and meter to my 12v/60W PV system.

Left it all day and the meter finally saw some power. (Though a 60W system should source 5A of power).

Spurred on by this I decided to drop a cable from the attic to one of my 24v/235W PV panels and then wired up two car batteries as the 24v load to the charge controller.

using 15A connector blocks

It's hot and nasty (itchy rock wool everywhere and loose boards) in the attic and the cables are close to the eave run - so little head room

But when I tested the open circuit voltage it was 0V !

My heart sunk. As I'm not sure if I tested all the panels when I received them.


So I tried another panel in the attic. It read 36V open circuit and so I connected it up. But again it read 0v down in the house. Below is the label at the back of each panel:

.

I'm hoping that my cabling is at fault. I'll go up on the roof with a voltmeter this Sunday and check all the panels before my extension cables.


I also found out that while the 300W pure sine wave inverter powers the lights in the extension it cannot get past the fuse box to the main house. I don't know why. Investigation is required.

Raspberry Pi system controller received

Finally received my long awaited Raspberry PI.

I registered my interest with RS Components on 9th March 2012. And was invited to place my order on 31st March 2012:

RS Stock No.	Qty	Description	Unit Price	Goods Value
756-8308	1	Raspberry Pi Type B Single Board Computer	£21.60	£21.60
			Running Total	£21.60
Tax				£4.32
Standard Delivery (Despatch expected within 6 week(s))				£4.95
Order total				£30.87

Just took over 3 months to arrive :)

However, I received it Saturday and fired it up and it looks good.

It provides two USB ports (nominally for keyboard and mouse) a RJ-45 ethernet port and a HMDI screen output.

I used my mobile phone charger as a power supply.

The O/S I downloaded to an SD card.

My aim is to use this as the heart of a monitoring/control system for the wind turbine and PV panels.

It uses 2W and is half the size of my hand. Perfect!