Tag: green

Air Quality egg – dust sensor – repeatable test case

More information as I am trying to get a handle on the problem.

I now have a 100% repeatable test case – making it easier to find out what’s going on.

When I connected my laptop via the USB cable and the USB BUB to the FTDI plug on the eggs motherboard everything suddenly worked – and the dust sensor started reporting sensible values.

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(AQE plugged into the original PSU)

As soon as I unplug the USB cable and plug the power supply into the power socket the dust sensor starts reporting zero ohms. To be on the safe side I used 2 different power supplies with the same results.

The I plugged the USB cable in – and the sensor again reports sensible (non zero) values.

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(Air quality egg plugged into USB cable to FTDI plug on motherboard)

I can now leave the USB cable plugged in (so that the board does not reset itself) and plug/unplug the PSU. I have done this a large number of times. And it is 100% consistent and repeatable. As soon as I plug in the PSU the dust sensor reports zero. But all other sensors continue to report normal values. ……….. I measured the voltage on the i2c plug the dust sensor is plugged into, and with the PSU plugged in it reports 4.96V, with power from the USB port it reports 4.85V. This may possibly be significant – the only other difference I can think of is noise from the PSU – but I have no other really good theories at the moment.

Anyone with any good insights? For the time being I will run the remote egg from a USB power supply via the FTDI port – not terribly convenient, but it works.

Air QUality egg – dust sensor mk II

After plugging in the new dust sensor I got sensible raw measurements, but R0 was zero – so after advice on this forum I reprogrammed the dust sensor interface board . This was made slightly harder by the board not having any programming headers in place.

But on running load.sh – everything bar the the first fuse setting seem to work. This first setting gives a error message :

“avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.01s

avrdude: Device signature = 0x1e9311 avrdude: reading input file “0xff” avrdude: writing efuse (1 bytes):

Writing | | 0% 0.00s ***failed;
Writing | ################################################## | 100% 0.04s

avrdude: 1 bytes of efuse written avrdude: verifying efuse memory against 0xff: avrdude: load data efuse data from input file 0xff: avrdude: input file 0xff contains 1 bytes avrdude: reading on-chip efuse data:

Reading | ################################################## | 100% 0.00s

avrdude: verifying … avrdude: verification error, first mismatch at byte 0x0000 0xff != 0x07 avrdude: verification error; content mismatch ” The dust sensor now reports 100 ohm for R0 – but zero for raw values.

Any suggestions for how to get it working again?

Air Quality Egg – Dust sensor

The Dust sensor arrived tonight for the Air Quality egg arrived today – and has now been installed, and the feed is working.

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(Click for larger image)

The measurements seem a bit wrong though – possibly the Dust_r0 of -1 is somewhat wrong.

Btw. I followed the instructions here for the physical installation. I will post pictures later.

Air Quality egg – making sense of the CO sensor

To sum up :

The air quality egg outputs 2 values per sensor – the raw resistance measured, and a interpretation of that based on a number of factors including a average calibration value (R0), humidity, temperature and a factory supplied set of graphs helping to turn the raw resistance value into a ppb (Parts per billion) value for human consumption.

So these are the values from our AQE (Now placed outside in a semi rural placing)

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and these are the values from another AQE in the UK (also placed outside in a rural setting)

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and as you can see – the raw resistance is not that far apart taken over time, but the interpreted values are extremely far apart.

I would expect both of these to show very small CO values, and there is clearly something wrong in the delta between the 2 interpreted graphs.

I suspect mine is wrong – as the values are way too high, especially seeing it’s windy outside, and the air “feels” good to me.

The manufactures of the AQE has a blog posting about how to set the R0 (or calibration resistance) of the egg to change the calculations – so that is one way of correcting the interpreted values, but it is a bit cumbersome, as it requires you to upload new software to the Arduino clone, running it, and the re-uploading the base station software. For experimentation this seems a bit long winded.

What I feel is needed is software to do this on my own computer – so I may have to sit down and get cracking on this – after all this is the real advantage of all the open source software!

The quest to calibrate a Air Quality Egg

It’s quite clear that I need to calibrate the sensors of the AQE before i get much sensible out of it. So starting with the CO sensor I have hunted around for a reference source and found this :

[From The use of a standard butane hair curler is an easy, safe source to use for a very low carbon monoxide gas concentration less than 500 ppm and can be used during calibration and testing.]

The only other way I could think of calibrating this is to use the Carbon Monoxide alarm we have in the house – it’s got a display that shows CO ppm over the last 3 weeks. According to the manufacturer it starts at 10 ppm.At the moment it shows 0ppm though – so maybe that’s one place to start….

airqualityegg – Data Quality

I am a bit puzzled by the data I’m collecting from my AQE – so I started reading up on the sensors and found the following

CO to 9ppm with an accuracy of 1ppm. Normal atmospheric ranges are up to 20ppm
NO2 to 100ppb with an accuracy of 1ppb. Normal atmospheric ranges are up to 400ppb
Etc

[From airqualityegg – Data Quality]

But what I’m seeing from my AQE is :

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Which would indicate that I should be dead. But as I’m still fairly active and feeling well I decided to look at someone else’s measurements

And I found one outside Chicago

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And after looking at a few others I concluded that the AQE sensors will indeed need a bit of calibration to deliver believable results.

This seems to require a bit of programming and changes to what is in reality “hard coded” values (i.e. they will need changes to code and data that will need to be uploaded to the Egg. So I would expect this to take some time – and I am glad that I have the tools to do this – as one of the first things I did after getting the AQE was to upload new software to the base egg.

Gas usage in our house

The gas usage in our house :

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As you can see from the graph (not easily mind you) over the first 6 months of the year we used almost the same amount of gas as during the first 6 months of last year. Not bad considering we have had a much colder start to this year, where we have actually used the heating in the house more.

At the moment we are down to the lowest gas usage for any period measured so far – with a average of 1.22 units per day over the last 72 days, which is almost 30% below the same period last year.

This is in no small part due to our refurb of our conservatory, which had 8 glass doors leaking heat through non-insulated gaps between the doors and the door frames. This has now been properly fixed, and we are seeing the results already.