When my import meter LED indicates 'reverse' (>40ms on ) what is the state of the 3.6KJ energy bucket a) when it lights, and b) when it extinguishes? Is the 'off' transition a chargeable tick?
If the charge is initiated at he next 40ms pulse, is the 'bucket' full, half empty or indeterminate when the reverse flow indication turns off?
While I wait for my CT to arrive from China, I have a notion for an algorithm to control an immersion heater via a SSR using info from this LED. I'm also thinking when the CT arrives, this light going off could be a backstop against my clever automatic parameter adjustments not being as clever as I thought and costing me money
If I get charged the moment it extinguishes then neither of these ideas is so hot!
My own experiments with a kettle show that turning the kettle on does not cause the LED to go out right away, so it certainly isn't an instantaneous indicator of reverse flow - or more accurately, does not indicate the end of reverse flow instantly.
My humble newbie apologies if this has been asked already, I did search the site, honest.
I know about the current (excellent) designs here but I've a weakness for re-inventing the wheel, especially if I can trim some hardware with some smart code.
Re: Meter reverse flow LED
It's all a bit of a moot point. For fairly obvious reasons, the meter manufacturers don't spell out exactly what they do internally, and as far as I'm aware, we don't have an insider who can tell us. I assume you've read about meters in Building Blocks, and Robin Emley's (calypso_rae) copious posts on his energy diverter http://openenergymonitor.org/emon/node/1757. Together, these pretty much sum up our knowledge on these meters.
Robin will be happy to supply you with a proven kit at a reasonable price, if you don't want to reinvent the wheel again you can use the published sketches, or you can write your own.
Re: Meter reverse flow LED
Thanks Robert, yes I've read read quite a bit on here, including Robin's posts. If I do achieve any improvements - I'm looking at simplification rather than efficiency, which is probably already optimal - it will be from standing on the shoulders of giants!
If no-one comes back with an answer, it shouldn't be hard for me to run an experiment on a sunny day,use a sketch to run the heater until the LED goes out 100 times and see if the 1/10ths digit increments. I'll post the results here (unless there's a better place). Don't hold your breath, I live in W. Wales! I was just hoping someone might have done this already.
I'm a software engineer, not an electrical engineer, so I'd like to keep the electrics as simple as possible. I guess I'll find out soon if you are right about cheap SSRs!
I'm planning to experiment without any voltage transformer and use the LED to determine when the flow reverses. I realise I won't get true power readings but I figure for a spare power diverter I just need to balance total current flow in and out within the 3.6kJ 'window', perhaps with a 'fiddle factor' for differences in power factor. I was hoping that code on the Arduino could adjust this dynamically if need be. If the LED going out doesn't add 1Wh to the bill, I can use that freely as feedback for the heuristics and for flow direction. If it does 'click over', I'll just have to be a bit more conservative with my 'guesses', and live with the fact that 'unexpected' flow reversals will increase my bill slightly. At 12p / 1000 'mistakes' I'll not lose any sleep over it.
If it doesn't work I may well end up buying one of Robin's excellent kits, but I like inventing - or refining others' inventions - nearly as much as I like saving money!