Smart meter.  Self install? - Page 1
Forum section: electronics / beginners

author: paulca
author_rank: Super Contributor
timestamp: August 15, 2020, 04:32:40 pm
content: So I'm thinking of installing one of these in my meter box.https://meters.co.uk/products/em-408-single-phase-modbus-meter-with-ct/It's a single phase smart meter. It's not a full current device, just takes L+N to sample voltage and power itself. Current is measured via a current transformer.I can't see any reason why I can't just put a normal mains plug on this and stick it in the socket in the electric cupboard.... can you? Do I even need to mount it in a DIN rail enclosure? If it's not wired into the consumer unit it's just a domestic electronic device with a coil clipped on the live tail....Just trying to save on having a spark install it.

author: Gyro
author_rank: Super Contributor
timestamp: August 15, 2020, 05:46:12 pm
content: It depends how you install it. There's no problem with clipping the current transformer around a meter tail. The mains input isn't doing anything more than powering the meter, so no, there's nothing stopping you from powering it from a ordinary fused mains plug.If you needed to hook into the consumer unit to get a mains supply then you would need a sparks, but if you already have a convenient socket, then there's no problem.You don't particularly need a DIN rail enclosure, although it makes mounting easier, and you can still get small plastic ones - you just need to ensure that the mains supply connections are insulated and properly strain relieved. A fuse wouldn't go amiss either, at least use a 3A or lower in the plug.

author: james_s
author_rank: Super Contributor
timestamp: August 15, 2020, 05:56:14 pm
content: I'm sure that would work, but why not just pop it into your panel as intended? I'm not familiar with UK laws but it's perfectly legal if not generally advisable for individuals to install that sort of thing themselves over here. It's not rocket science, unless your panels have some kind of tamper seal just do a tidy job and nobody will ever complain.

author: paulca
author_rank: Super Contributor
timestamp: August 15, 2020, 06:06:34 pm
content: Quote from: james_s on August 15, 2020, 05:56:14 pmI think it comes down to insurance. If something goes on fire and burns the house down. The insurance will look for any excuse. Uncertified installation work would be one of them. By not "installing it" and instead adding it as a consumer device I can jink round that.

author: kaz911
author_rank: Super Contributor
timestamp: August 15, 2020, 06:33:13 pm
content: In the UK if you are a "competent person" you can install more or less anything in your own home.It is NOT illegal to plug something into the consumer side. It is not illegal to put clamps on the inboundYou can NOT create new power groups - but you can extend existing - so adding a new plug socket downstream on a group is legal - adding a new group is not.Anyway - I have the old version of this :https://loop.homes- that is a power meter that clamps on and plugs in and keeps you updated with info via phone for GBP 50,-They have gone from pure engineering company before - aka hardcore website - to a very consumer website and new apps.But I can't fault the hardware. Runs fine now on 3rd year without battery replacement on the wireless sensor.But I find their current website ... OTT...

author: james_s
author_rank: Super Contributor
timestamp: August 15, 2020, 06:34:06 pm
content: Can you not get a permit to do the work yourself? I've replaced several panels (consumer unit) and even the entire service entry with the mast and meter base myself, had to get a permit and have it inspected and signed off but that was not a major obstacle. As far as insurance, you might encounter the same problem if they find you've got something meant to go in the panel sitting in the cupboard plugged into a wall socket. That's insurance for you.

author: paulca
author_rank: Super Contributor
timestamp: August 16, 2020, 02:34:00 pm
content: The RS485 link from it is just 2 wires, I know there is a lot of discussion about this before and after I read that thread I felt like I knew less.The idea was for me to make a short 12 inch tail using CAT5 and just send the single pair to a MAX485 breakout board, then uart to the ESP8266 to publish in the network.Those low voltage electronics will almost certainly be running on a switch mode power supply and thus possibly floating at around 100V.Should I ground the low voltage digital stuff? If so, how?

author: Gyro
author_rank: Super Contributor
timestamp: August 16, 2020, 09:55:05 pm
content: There doesn't seem to be much information in the manual on the RS485, but if you reference your RS485 terminator to your local ground then the meter's logic ground reference should follow.Best to check with the manufacturer though.

author: paulca
author_rank: Super Contributor
timestamp: August 17, 2020, 07:55:38 am
content: It's okay. When I went to order the meter, they wanted £50 postage. So I found an alternative that doesn't require the 485 bridge with cheaper (free) shipping. A Shelly EM. It's already ESP8266 based and flashable, but the build in firmware has an open API and no reliance on "cloud", so fingers crossed.

author: Gyro
author_rank: Super Contributor
timestamp: August 17, 2020, 11:59:46 am
content: QuoteOuch! They're supposed to be in the UK. Charging £50 postage for a £49 device is just a sneaky way of generating interest in a £100 product.Glad you found something better!

author: Monkeh
author_rank: Super Contributor
timestamp: August 17, 2020, 02:20:16 pm
content: Quote from: paulca on August 17, 2020, 07:55:38 amCode:Subtotal£49.00Shipping Royal Mail <1kg: £3.70VAT£10.54Total£63.24...?QuoteUnfortunately they make no attempt to specify accuracy or indicate if it's capable of determining the direction of power flow.

author: paulca
author_rank: Super Contributor
timestamp: August 17, 2020, 05:11:55 pm
content: Quote from: Monkeh on August 17, 2020, 02:20:16 pmIt's probably as I'm in Northern Ireland. In some cases the shipping cost look up can't work it out as they have a GB, not UK destination list and everywhere else defaults to "other". In other cases they use a carrier who charges an NI surcharge.... because it basically involves getting it on one of the over night flights. This is becoming rarer though.In this case it's likely it couldn't work out where I was so defaulted to £50 shipping.For the Shelby I don't really need high accuracy, just indicative monitoring. It has two clamps and I've spotted people using them to measure solar and mains. I don't know about direction, but I'm sure I've seen people setting it up and getting negative current.

author: Monkeh
author_rank: Super Contributor
timestamp: August 18, 2020, 04:18:03 am
content: You've inspired me to get off my arse and do similar myself as I've wanted to for ages. I'm going to pick up a similar meter from Eastron (via the slow boat, so it should be this year at least..).I shall show the final result, assuming I get it finished.

author: paulca
author_rank: Super Contributor
timestamp: August 18, 2020, 04:24:00 pm
content: Quote from: Monkeh on August 18, 2020, 04:18:03 amThere is a build thread (ish) where I created an RS485 -> Wifi dongle using an ESP8266 and MAX485 board. Just in case you are looking for ideas and getting a ModBus meter. Careful as there is now, M-Bus which is Meter Bus and not RS485.

author: BillyD
author_rank: Regular Contributor
timestamp: December 30, 2020, 05:58:20 pm
content: Quote from: paulca on August 15, 2020, 04:32:40 pmI bought this EM-408 myself and have been poking around with it recently.Took a lot of messing around to get it doing anything as I'm not very knowledgable about modbus, and there's not a lot of documentation about this device.Main pitfalls for me were that the serial protocol of my unit is 9600 baud, 8 data bits, Even parity, 1 stop bit whereas the Arduino which I was initially using has parity Off.Also I was using SoftwareSerial, and its timing was skewed enough to corrupt the data.The other painful thing about modbus is that if you do anything wrong, it just doesn't respond, so troubleshooting is not much fun.All works fine on both arduino and esp8266 now that I've figured out the correct parameters and used the hardware uart.As to whether you could plug it into an outlet as opposed to wiring it into the DB, you could if it's more convenient.Main thing is that ideally that you want the unit to be getting the exact same voltage as the point where the CT is mounted, so that your wattage figure is accurate.Depends on the wiring and loads between the CT and the place where you plug your unit in.

author: carl0s
author_rank: Unknown
timestamp: January 02, 2021, 06:07:42 pm
content: did somebody mention current transformers for energy monitoring?

author: paulca
author_rank: Super Contributor
timestamp: January 02, 2021, 06:17:43 pm
content: Quote from: BillyD on December 30, 2020, 05:58:20 pmIs modbus not RS485 as opposed to RS232 UART? I didn't think they were even electrically compatible.I spotted this on my travels, there is mbus and modbus. The former is for sending meter readings from meters for energy retailers to install. modbus is the industrial long range RS485 control/telem protocol.

author: BillyD
author_rank: Regular Contributor
timestamp: January 02, 2021, 07:38:45 pm
content: Quote from: paulca on January 02, 2021, 06:17:43 pmWell not exactly, as Modbus is a protocol whereas RS485 defines the voltage level on the bus. Yes it is very commonly used over rs485 bus alright, but apparently is also widely used over IP.So in my case I used a MAX485 ic to connect the serial pins on an arduino (and later an esp8266) to the rs485 bus on the EM-408 meter. Modbus is geared towards reading and writing pins and registers in devices on the bus - and it could be any device, not specifically meters. In my case I was querying registers on the meter to get current/volts/power factor/etc. To do this I simply write 8 bytes to the bus comprising the (1) id of the target device, (2) the command ie 'read register', (3) the offset of the register, (4) the number of adjacent registers to read and (5) a checksum for these bytes. Then I wait for a response to appear on the bus - ie the max485 converts the rs485 signals to tha appropriate voltages to connect to the rx pin on my microcontroller.