Hi
I have had a search round on this site and others for information in reading the data from my Electricity Meter.
I found this http://arduino.cc/forum/index.php/topic,22225.0.html topic but it was closed so I could not reply to it.
I just got into arduino kit (In the past week or so) and have done the usual experiments temperature probe, RTC, LED Blink etc. But now I wish to move on to what I wanted to do.
I installed 3.75KW of solar on my house and I wish to monitor not only how much I produce but how much I export. I have two electricity meters the First is An Elster A100C this is the one I had fitted and measures my "GENERATION" i.e. the Total energy produced by the PV. I have managed to read this meter after reading this Electricity Meter Reader article. It worked almost first time using a just an uno and a TSL261 TSL261 Datasheet(PDF) - List of Unclassifed Manufacturers PhotoIR optical sensor. This meter constantly transmits its data about once every couple of seconds or so so was pretty simple to read.
The second meter I have is the one fitted by NORWEB my electricity supplier this records both my "IMPORT" i.e. the electricity I get from the grid and my "EXPORT" i.e. the excess electricity I produce that goes back to the grid. Unfortunatly this meter only displays the "IMPORT" figure but I am reliably informed that deep in its registers are the "EXPORT" values too.This meter an Ampy 5196A I have had some success in reading this meter too. I used the TSL261 as a receiver and this http://dx.com/p/38khz-ir-infrared-transmitter-module-for-arduino-135040 as my transmitter. Before I dived into reading the meter with the UNO I thought I would see if I could read the meter with a PC using a USB to TTL adapter (cp210x).
I hooked it up as follows.
Serial adapters tx Pin ----> signal pin on the transmitter
Serial adapter Ground -----> Transmitter Ground
Serial Adapter RX Pin <----- Receiver Signal Pin
Serial Adapter Ground ------> Receiver Ground
Serial Adapter 5V -----> Receiver VCC
I opened up "termite" and sent /?!{cr}{lf} to the meter at (300 Baud 7Bit Even Parity One Stop Bit) but no joy :0 , other than /?!{cr}{lf} being received back by the receiver (Echo was turned off). After a little head scratching I had a flash of inspiration, I thought what happens if the "1" should be "0" and vice versa. So I dug out a 74c04 Hex Inverter and inverted both transmitter signal and the receive signal. I opened up "termite" again and sent the command 20 or so times and eventually got a reply something on the lines of /AMP05196A-21 (I think). The receiving was very Hit and mis only got a reply about 7 or 8 times out of about 100. The transmission was working though as the meters Red led flickerd for about 5 seconds every time I sent the command. The receiver seems to need to be pointed precisely at the RED led to work, at first I thought the TSL261 may need amplifying. In writing this post I found this http://www.abacuselectrics.com/f6zd09r.pdf data sheet It appears that my Utility company have fitted one of the only meters that replies in the RED spectrum not the IR spectrum. There must be just enough IR being emitted to operate the TSL261 if the wind is blowing in the right direction and I balance on the right leg.
My original question was going to be can I invert the tx/rx serial port signals in the "UNO" in software or am I still going to need to still use an inverter. I figure I can get away with an inverter for the transmitter by connecting it like so.
UNO tx Pin ----> Ground transmitter
UNO 5V -----> Signal Ground.
Thus when the TX is low the LED will be transmitting.
My second question, In the light of my RED/IR discovery is, Am I best trying to amplify the TSL261 output or can someone recommend a TSL261 equivalent for RED light and am I going to have to stop daylight getting to it.
I have a copy of the IEC 62056-21 specs and getting the data out of the meter is relatively simple one you have the optical probe. I hope that this will allow access to the data IEC 1107 optical port for less than $10 rather than the $80-100 everyone seems to charge for the a probe. This would be more accurate and simpler to implement than say a CT clamp.