Arduino Electricity data logger - converting for gas meter.

[solarbot]

Hi,

Thanks for the info on this post: http://www.navitron.org.uk/forum/index.php/topic,8881.0.html regarding the magnetic pulse produced by the newer gas meters in the UK.  Our meter is fairly new and has and LED that I was hoping to use but alas in never pulses - so news of the potential to pick up a magnetic pulse is interesting & encouraging.  I'm hoping to get the meter logged before this years heating season.

I'm hoping to convert this: http://www.airsensor.co.uk/component/zoo/item/energy-monitor.html to pick up the magnatic pulse.  Seems that most people have been using reed switches for this purpose - I'm wondering if anyone has had any success with Hall Effect Sensors for this application....?

[johnrae]

If you use a small compass you'll be able to trace where the magnetic source is.  On some meters it's at the end furthest away from the lowest digit.
The beauty about reed switches is that they are completely passive devices so require no power (apart from the fact they are switching a very low current signal)
jack

[solarbot]

Thanks Jack - I will try the compass trick.

I'm hoping to go down the Hall Effect route as it should avoid problems caused by debounce/false counts that are common with mechanical switches - although the passive nature of a reed switch is very attractive :-)

[tz0c0s]

Although I don't recall how, a debounce circuit was very easy to construct when I had a fair few to make yearrsssss ago.

Regards Andy

[roscoe]

solarbot,

what is the manuf/model of your gas meter ?

[solarbot]

Hi Roscoe,

The meter is an Actaris - SC6

[KenB]

Solarbot,

If it's an Actaris, it is probably similar to mine.  They are described in the industry as "pulse ready" - which means that they can have an optional pulse module fitted to the index (the dials on the front).

If you look at the index, the least significant zero digit is probably silvered. If this is the case - it is intended for opto-reflective sensing - not magnetic.

However this Ofgem document is a discussion with Actaris about a magnetic pulse ready index - so both types may exist?

http://epr.ofgem.gov.uk/document_fetch.php?documentid=12953

Here's how I managed to get a pulse count out of mine - using an opto-reflective  photosensor

http://sustburbia.blogspot.com/2009/11/using-arduino-to-monitor-gas.html



Ken

[KenB]

There's certainly a magnetic sensor available for Actaris U6 meters manufactured after January 2010. Prior to that I have my suspicions that they intended to use an optical sensor.

http://www.stream-measurement.com/5473/products/7424/lf-pulse-module-for-itron--actaris--u-series-gas-diaphragm-meters.aspx

And this document from National Grid - describes the meters they use including the SC6

http://www.nationalgrid.com/NR/rdonlyres/85E91846-F0F6-46B8-8C71-2DEE958A5AFD/37684/MeterTypes_Oct2009.pdf   with a picture of the SC6 index at the bottom of page 2 - showing the silvered zero.


Hope this helps,



Ken

[roscoe]

Fairly sure the meter will have both silver blob and the internal magnet pulse.

Just as Ken has said there is a clip on block for this meter for a few pounds more, if you don't has the DIY motivation.
Not 100% sure but this is worth a further look at £26.50.  Sure a reed switch is cheaper but you have to design some way of mechincally mounting it.

http://www.utilitymeterswarehouse.com/pulse-block-for-itron-actaris-sc6-tvi-meter.html/

[solarbot]

Hi Ken & Roscoe,

Thanks for the great info - our meter certainly has the silvered 0 so could look at the optical route (perhaps has a high energy demand for a battery operated data logger?) - I have just installed my bike computer on the meter so hopefully it will pick up any magnetic pulse available in miles :-)  We have just installed 21 solar thermal panels at our local community swimming pool - by chance the gas meter was changed at the same time.... now this does have a electical pulse output so that one will be easier - we hope to be able to see when the gas boiler is kicking in and hopefully optimise the pool termperature until we get as close to 100% solar input as possible :-) - the rest of the system is fully rigged with the Resol data logging unit - very impressed -all good fun & worthwile.... a nice combination.

[KenB]

Solarbot, Roscoe,

Further experimentation with the Actaris meter and pulse counting.

I have used a Hall effect sensor (Farnell 178-4735 http://www.farnell.com/datasheets/621734.pdf ) clipped exactly in the same place as the optoreflective switch.

The Hall sensor is mounted so that the face with writing on it, which is triggered by a passing North pole is pointing towards the least significant digit wheel.

This wheel contains the magnet, roughly in the same position as the silver reflective zero digit.

The hall sensor will work from 3V or 5V systems and needs a 10K pull-up resistor because it is open-collector. 

As the magnet passes, the open collector output goes cleanly to 0V.   Many of my problems with the optical sensor was due to signal bounce and noise pick-up. This inexpensive Hall sensor seems to have cured all that.

To connect up you will need a 3 way cable,  or if running a long distance - something like screened microphone cable would be suitable.

I'm still testing to make sure that my pulse bounce and false counting problems have gone away - it's interrupt code on the Arduino, so needs careful debugging to make sure its  working correctly.

This gas logging ( and central heating control and monitoring)  is all part of the work that I am doing on the Open source Navitrino project.




Ken

[Brandon]

ken, again well done.  You are a wealth of knowledge and ability, I applaud you!

[KenB]

Brandon,

I was just following Roscoe's "hunch" that there would be a magnet in there too.

Applying a bit of deduction - the logical place to put the magnet would be in the lowest digit wheel.  After that, it was easy to confirm the suspicion using one of the Hall sensor devices which I had left over from another project.  It is very easy to build on a scrap of stripboard - pictures to follow later.

As a general point, there still seems to be a possibility of false triggering, making the pulse count total run ahead of the actual total on the gas meter index.

This will either need a Schmidt trigger (74HCT14)  or a debounce circuit made from Schmidt Nands (4093) to cure it in hardware

http://en.wikipedia.org/wiki/Schmitt_trigger

Alternatively the interupt service routine on the Arduino needs to qualify in firmware that it sees a pulse of minimum duration and not a string of short duration false triggers.


Ken


EDIT - Of course credit should actually go to forum member MikeM, who learned from the Automated Home forum about the magnet in the lowest digit  on the Actaris G4 meter - back in January and shared it here - and used an adapted pedometer to display the count.

http://www.navitron.org.uk/forum/index.php/topic,8881.msg104021.html#msg104021

It's a shame that a lot of the knowledge in these threads gets missed or forgotten as time pases

[solarbot]

Hi Ken,

That's great news - I have been trying to find a pulse with my bike computer but nothing so far - I suspect that the pulses are too slow for the bike computer so I will try your sensor suggestion.... I have some of these which I will try: http://www.active-robots.com/products/parallax/melexis-90217-halleffect-sensor.shtml .  Will report back.....

I have been following your Navitrino project - very impressed, great and valuable work - thanks for sharing it.

[KenB]

Solarbot,

That is very similar to the Honeywell sensor I use.   Position it so that the markings face the reflective digit.

I used a 10K pull-up resistor - Melexis datasheet suggests 5K6 - but I suspect that this is not crtical.



Ken