Energy monitoring device design required - Page 1
Forum section: electronics / projects

author: GeoffS
author_rank: Unknown
timestamp: March 24, 2012, 07:34:45 am
content: Now that the cold weather is here (arrived early this morning, I can see snow on the nearby peaks brrrr!) I thought I'd start an indoor project as the shed is too cold to work in.An energy monitoring system has been selected as the lucky candiate. There's lots of these around but I like the open source one fromOpenEnergyMonitor.org.. It''s Arduino based using 433MHz or 915Mhz wireless communications. Typical sensors are current transformers with an optical detector for use with smart meters.The problem I have is that my meters are older analogue, rotating disk type so I need a reliable method to detect disk revolutions (266.6 revolutions per KWH) I've found a few LED based detectors after a bit of browsing but some of them are a bit rough and unreliable.SoI thought, if there's anywhere to ask about this, it's here.Before anyone points out that the wires are visible and that I could connect current transformers to them, it's illegal to do such a thing unless you're a licensed electrician and I doubt that an electrician would install a device behind the insulated layer end bring wires out to the front, even though those CT's have no electrical connection. Smart meters are being rolled out but only for new installations or to replace faulty meters. As you can see from the meter box, I have three very similar meters and some sort of timer switch.What I'm looking for is a simple design for an optical sensor. The disk has a black mark on it so that the rotation can be seen and it's behind glass. The device also needs to unobtrusive so that the meter readers don't report it. Another thing is the the data transmitter unit is battery powered so power consumption is to be considered.So get your thinking caps on or get get your fingers googling and do my job for meThere may be a small prize for the best optionImportant: I'm sure that someone will suggest just going ahead and connecting up what I want. It's not just against the electricty suppliers rules but it's also illegal as far as state legislation goes so I won;t be doing that (penalties can include fines and if someone is seriously injured, incarceration!)

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: March 24, 2012, 10:40:31 am
content: Hi GeoffWelcome to Hobart, a bit of early winter weather.I don't know if you realise, but if the energy supply company looked at that photo, they could find out who you are from the meter ids in the photo. They are overworked and understaffed but one thing they can do is read a meter id.Luckily you weren't thinking of doing anything against the rules anyway.Do you actually want a log of your usage or don't you trust the power supply company.I checked the calibration of my meter a while ago, just by switching on/off known loads. By my calculations it was a fair bit out but I must admit that I haven't bothered to sort it out anyway.I noticed that you have no RCD protection in your fusebox, if you are playing around with Electricity you should get some put in. Or at least put anything experimental off an RCD protected powerboard.You can get an approved type of chinese power logger that can be inserted into your switchboard, I am not sure what it is called, I'll get the details if I can. you put them on each circuit. From memory $40 each if you import them yourself.I dont know how you interface to them though.

author: GeoffS
author_rank: Unknown
timestamp: March 24, 2012, 11:13:04 am
content: You're right, that the sort of thing petty minded bureaucrats would do - fixed.I have sent a question off to Aurora (the electricity supplier) to ask about monitoring and what is/isn't permitted. Although I made it very clear that there's no electrical connection involved, I'm sure I get the canned response about only having licensed people working on electrical installations.Even though I have no intention of doing any electrical work. the lack of RCDs was a surprise. Not sure if the two Clipsal MCBs are RCDs as well? They're only connected to the heat pumps. There is a sub-board upstairs where the fuses (no circuit breakers) for lights, power, stove and hot water are located. No RCD's there either. It's a rented house so I might check into that. I did have the electrician out when I moved in as the shed is on a separate feed and hadn't been connected for some years. Despite the ancient fittings there (3 phase), they did minimal remedial work and the power was turned on without issue.I'll be going ahead with the Open Energy Monitor any way and will be able to monitor most things via clip on CTs, it's just that the meter monitoring would make it complete. This being my first winter in the house, I'm keen to see just how much it costs to heat and whether I should be investing more money in woodBTW, I'll also be using the OEM stuff for weather monitoring.

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: March 24, 2012, 12:07:44 pm
content: We have a weatherboard house and a good wood stove, we burn about 4-5 tonnes a year.With those 100A current sensors, I don't think they can be very accurate on your normal loads.Considering you are not running electric heating, you are probably only using 50 amp hours per day.Your fuses are probably only 20Amp, it might be better to get some 20 amp versions of the sensor.If you find the manufacturer, I think they even go down to 5 amps.And as you are a global moderator or somesuch I guess you realise that you have to split out the active wire to put the ct sensor on.(Just checking, it could be a problem on some circuits.)

author: GeoffS
author_rank: Unknown
timestamp: March 24, 2012, 12:27:58 pm
content: I can't use CTs for the switchboard - as mentioned so don't need high current ones.I plan to use CTs for appliance monitoring so 10A will do the job, pretty sure I can get these from somewhere like Seeed.The only place I might want higher current CTs is for monitoring the stove. Problem there is that the wires are not accessible.from inside soI need to look under the house to see what's what.Good to know about the firewood, My place is two story, weatherboard, built into a hill (2 story at the front, 1 at the back). I got 4 tonnes which might be a bit on the low side.