Open Energy Monitor

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rexnanet
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Re: Open Energy Monitor

Post by rexnanet » Mon Feb 27, 2017 10:38 am

I'm also starting a energy monitoring project :)

As ESP8266 already has a emonTX lib I thought "why not adding an external SPI ADC and that's it???" :D

I though of using MCP3008 (75-200Ksps) and 8 channels. Should be ok.

But now I've read some of the posts on this thread and realized that might not work so great...
I think it doesn't support multiple sample-and-hold so reading one channel and then another will introduce some error... Is that meaningful at these rates?

If it's not an option I'll go for ESP8266 + STM32F103 option.

P.S. I've just saw people using ADS1115 (860SPS) but probably power measurements are not accurate (or even done)...

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RogerClark
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Re: Open Energy Monitor

Post by RogerClark » Mon Feb 27, 2017 10:47 am

rexnanet wrote:I'm also starting a energy monitoring project :)

As ESP8266 already has a emonTX lib I thought "why not adding an external SPI ADC and that's it???" :D

I though of using MCP3008 (75-200Ksps) and 8 channels. Should be ok.

But now I've read some of the posts on this thread and realized that might not work so great...
I think it doesn't support multiple sample-and-hold so reading one channel and then another will introduce some error... Is that meaningful at these rates?

If it's not an option I'll go for ESP8266 + STM32F103 option.

P.S. I've just saw people using ADS1115 (860SPS) but probably power measurements are not accurate (or even done)...
I did consider using the ESP8266 but the issue with just one ADC or needing an external multiplexer or external ADC

You can get a Blue Pill for $2, which is far cheaper than that ADC or even an external multiplexer, and with either of those ESP8266 + external devices options, the sample rate is going to be a lot lower than you get using the STM32F103 to sample the data.

BTW. Although I planned to use an ESP8266 to transmit the data, I found that where I needed to put the TX boxes, was out of wifi range, as it was in the garage, so I ended up transmitting the data to another board using 433Mhz.

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rexnanet
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Re: Open Energy Monitor

Post by rexnanet » Mon Feb 27, 2017 11:16 am

RogerClark wrote: You can get a Blue Pill for $2, which is far cheaper than that ADC or even an external multiplexer, and with either of those ESP8266 + external devices options, the sample rate is going to be a lot lower than you get using the STM32F103 to sample the data.

BTW. Although I planned to use an ESP8266 to transmit the data, I found that where I needed to put the TX boxes, was out of wifi range, as it was in the garage, so I ended up transmitting the data to another board using 433Mhz.
Ok, that seems a good option.

So what are you using as a server? the Raspberry pi or are you sending to emoncms.org?

Using the STM32 as an "ADC" the data is sent by RS232 to the ESP, right?
I'm hoping to get the ESP8266 to send the data to the Raspberry Pi and have it all "locally, inside the house".
I'm going to monitor the electrical "cabinet" and it's inside the house so it's in range...

I also thought using NRF24LE1 as it has an MCU with ADC and also the wireless part and have another NRF near the Raspberry and send data through RS232... Still looking for the better approach...

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RogerClark
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Re: Open Energy Monitor

Post by RogerClark » Mon Feb 27, 2017 8:25 pm

I dont have a central unit like a RPi etc, I have separate display units I made using Maple minis and the ILI9341 display.

All my system does is read the power and broadcast on 433MHz, once per second.

Multiple receiver units around the house display the power.

I was intending to add power control to this system, and I built a power controller capable of modulating a hot water heater, but I never ended up deploying it, because I designed and built it for my sister and my parents to use, but circumstances changed and it was no longer practical to deploy it.

The system was intended to functional where the Emon Tx was the master arbiter and the power controllers would request and be allocated a specific number of watts by the Tx unit, by communicating over 433MHz.

But I still had a huge amount of work to do on it, and it wasnt worth continuing with at the moment.

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rexnanet
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Re: Open Energy Monitor

Post by rexnanet » Wed Mar 01, 2017 10:45 am

Oh, ok. I thought it was solely based on a emoncms "scheme".

I'm going to try the ESP8266+MCP3008+emoncms.org approach first because it's simpler.
If it fails I'll change the MCP by the STM32.
And then when I have results I'll change the web server by the Raspberry Pi to keep the data more "private" :)

The local displays are also a nice feature!
I'll have to think about it but maybe adding a TFT to the raspberry as I already got one (only need to get it to work :) )...

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RogerClark
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Re: Open Energy Monitor

Post by RogerClark » Wed Mar 01, 2017 8:22 pm

The local displays work very well, but they have to run from a 5V PSU because I am using the ILI9341 display which is back lit LCD and hence takes too much current to run from batteries.

If you know of large black and white ( non backlit) LCD display, let me known, as Id like to do a battery version of the display.

I am also thinking of adding Bluetooth transmission to my design, so phones and tablets could be used as the display via a simple App.

I could move the whole monitor to the nRF51822, but as I already have multiple systems working fine, it would be easier for me to add Bluetooth to the existing hardware

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rexnanet
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Re: Open Energy Monitor

Post by rexnanet » Wed Mar 01, 2017 8:34 pm

As for the power, I know, it will be powered from a USB wall adapter.

Big ones I don't know but tou could run multiple nokia 5110's. They are reasonably cheap and you could put one digit on each and be readable :)
Other than that only e-paper. There are 6inch displays from the older kindles that are cheap now. I think some guy got it to work with a raspberry... I dont know if it would work with a microcontroller...

If you uploaded some info on emoncms.org you would already have the GUI made and logged history... But its not a big deal.

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RogerClark
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Re: Open Energy Monitor

Post by RogerClark » Wed Mar 01, 2017 8:43 pm

Thanks

I use those Nokia displays on some other projects, but they were too small for this, but i like the idea of 1 digit per display.

I looked at ePaper, but at the moment its expensive because you need a driver board as well as the display.

BTW
I still think using a Blue Pill as the ADC and to calculate the power is cheaper and better ,than using and external DAC or multiplexer, but the choice is yours ;-)

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rexnanet
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Re: Open Energy Monitor

Post by rexnanet » Wed Mar 01, 2017 9:19 pm

In this case the external ADC is cheaper ;) around 0€ ;) lol
Thats why I considered it.
Dont think these are the ones I saw the first time but they vive an idea:
https://hackaday.io/project/13327-teens ... pter-board

https://hackaday.io/project/4446-e-ink- ... pi-display

zmemw16
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Re: Open Energy Monitor

Post by zmemw16 » Wed Mar 01, 2017 9:24 pm

RogerClark wrote:Thanks

I use those Nokia displays on some other projects, but they were too small for this, but i like the idea of 1 digit per display.
probably not, consider 7 segment displays, istr seeing 6" ones somewhere. current consumption - i've no idea
srp

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