Sensair S8

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manjh
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Sensair S8

#1 Post by manjh » 22 Aug 2017, 00:02

No question or problem this time, but a post to share how installing a Senseair S8 CO2 sensor has worked out for me.
Technically this is easy as pie. Connect Vcc (5V!) and ground, and the two data lines to two GPIO's (D7 and D8 in my setup).
In Domoticz create an "Air quality" device, and in ESP Easy a device for the hardware (using the idx from Domoticz).
Schermafdruk 2017-08-21 23.44.04.png
Schermafdruk 2017-08-21 23.44.04.png (97.33 KiB) Viewed 2606 times
Looking at the ESP Easy interface I could see the Co2 value, in Domoticz it stayed zero.
Then tried a "custom sensor" in Domoticz, and the value came in very nicely. But not in the correct format where a value gets a textual property: excellent, fair, etcetera.
So I created a small script that copies the value into the "air quality" device. That works. Not a real solution, but more of a workaround. OK for now.
Here's the script:

Code: Select all

-- this script will copy CO2 values from the hidden custom-sensor device into the AIrQuality device

commandArray = {}

if devicechanged['$Dummy CO2'] then
    val = tonumber(otherdevices_svalues['$Dummy CO2'])
    commandArray['UpdateDevice'] = otherdevices_idx['SenseAir S8 CO2']..'|'..val..'|0'
end
--   commandArray['UpdateDevice'] = otherdevices_idx['SenseAir S8 CO2']..'|999|0'

return commandArray
Later (thanks to a suggestion from grovkillen :) ) I changed this setup into a simple rule in ESP: this eliminates the need for a dummy device in Domoticz, and a running script.
Here's the rule (including a line for my BMP085):

Code: Select all

On System#Boot do 
  timerSet,1,30
endon

On Rules#Timer=1 do
  SendToHTTP,10.0.0.199,8080,/json.htm?type=command&param=udevice&idx=1808&nvalue=0&svalue=[BMP085#Temperature];[BMP085#Pressure];0  
  SendToHTTP,10.0.0.199,8080,/json.htm?type=command&param=udevice&idx=1806&nvalue=[S8#PPM]
  timerSet,1,30
endon
When this worked (setup on a breadboard) I added a few more sensors just for the fun of it: DHT22, DHT1750 and BMP085. I know, not the most up-to-date, but this is what I had lying around.
I put the whole setup in my living room and let it measure for a while.

What strikes me is how easy it is to draw conclusions. Also, how "different" this sensor is. I don't know for sure, but I suspect many of us are "techies": we love to play around with things and make it work, and then sort-of loose interest. The fun is in the building of the unit.
But this is different.
I can draw conclusions from the measurements, and can see new applications on the horizon.
Look at the graph below, specifically the last two days (the graph before that is contaminated by measurements during setup).
Image
I can see the CO2 value being low, until the evening starts (this is when we are in the living room, two adults). Then around midnight we turn in and the value slowly drops. In the morning, I get up and open up the large doors to the garden to let the summer in: the CO2 value immediately sharply drops.

How can we use this: rising CO2 value indicates people present, and could influence the switching of lights (OK, I admit: there are better ways to do this). But more importantly, I could link the value of the CO2 level to a ventilation system: turn it on when the value rises above a set value, turn it off when it is under another set level.

The only downside of this sensor: it is not cheap. I found prices in China of $54 and up. A steep price, but when you think of what this little device does... :)

(As soon as I have some time, I will update the Wiki page for this setup)
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Last edited by manjh on 22 Aug 2017, 10:04, edited 5 times in total.

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Re: Sensair S8

#2 Post by grovkillen » 22 Aug 2017, 06:29

Thanks for a great review. Regarding the air quality device in Domoticz, can't you add a rule instead of using a script?

https://www.domoticz.com/wiki/Domoticz_ ... ir_quality

https://www.letscontrolit.com/wiki/inde ... th_own_IDX
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Re: Sensair S8

#3 Post by manjh » 22 Aug 2017, 09:45

grovkillen wrote:
22 Aug 2017, 06:29
Thanks for a great review. Regarding the air quality device in Domoticz, can't you add a rule instead of using a script?

https://www.domoticz.com/wiki/Domoticz_ ... ir_quality

https://www.letscontrolit.com/wiki/inde ... th_own_IDX
I could give it a try. You know how it is, once you find a workaround you leave it at that. :x
But using a rule would be "cleaner" I think.

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Re: Sensair S8

#4 Post by manjh » 22 Aug 2017, 10:05

grovkillen wrote:
22 Aug 2017, 06:29
Thanks for a great review. Regarding the air quality device in Domoticz, can't you add a rule instead of using a script?

https://www.domoticz.com/wiki/Domoticz_ ... ir_quality

https://www.letscontrolit.com/wiki/inde ... th_own_IDX
Tried it, and it works. Funny thing is that I already had taken that path for my BMP085... so it fits in very nicely.
Thanks for the suggestion!

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Re: Sensair S8

#5 Post by grovkillen » 22 Aug 2017, 10:14

manjh wrote:
22 Aug 2017, 09:45
You know how it is, once you find a workaround you leave it at that. :x
I do know :) That's why I asked. :geek:
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Re: Sensair S8

#6 Post by manjh » 22 Aug 2017, 10:18

grovkillen wrote:
22 Aug 2017, 10:14
manjh wrote:
22 Aug 2017, 09:45
You know how it is, once you find a workaround you leave it at that. :x
I do know :) That's why I asked. :geek:
As the Brits say: birds of a feather... :D

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Re: Sensair S8

#7 Post by grovkillen » 22 Aug 2017, 10:24

Stick together. 8-)
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Re: Sensair S8

#8 Post by manjh » 11 Sep 2017, 09:44

This sensor has a great wow-factor. With most other sensors, you are excited immediately after installation, and then get used to it.
The S8 still surprises me.

Check out the screenshot below. Before, I've already recognized the daily peaks, every evening the doors and windows close and we are staying in the livingroom. Hence the CO2 level goes up: 2 adults breathing is enough for this sensor to measure in a room of about 70 square meters.

But now check out the enormous peak on September 10th!
It was quickly explained: an evening at home, watching a movie, with 10 or 12 candles lit. Check out the CO2 output of those!

Image
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Re: Sensair S8

#9 Post by grovkillen » 11 Sep 2017, 12:25

Yes, the candles are a big oxygen consumer... :?
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Re: Sensair S8

#10 Post by manjh » 11 Sep 2017, 12:26

grovkillen wrote:
11 Sep 2017, 12:25
Yes, the candles are a big oxygen consumer... :?
I know, but in a room this size, I did not expect the effect to be really measurable... :shock:

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Re: Sensair S8

#11 Post by TD-er » 18 Sep 2017, 13:13

I also noticed the CO2 level to rise dramatically fast when cooking (on gas).
Our kitchen has no door to the living room, so concentration becomes equal in those rooms. (12 + 25 + 10 m^2 in total)
Let's say, it is good my CO2 sensor has a range from 400-5000 ppm, since it can spike over 2000 ppm in no-time.

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Re: Sensair S8

#12 Post by manjh » 18 Sep 2017, 17:28

TD-er wrote:
18 Sep 2017, 13:13
I also noticed the CO2 level to rise dramatically fast when cooking (on gas).
Our kitchen has no door to the living room, so concentration becomes equal in those rooms. (12 + 25 + 10 m^2 in total)
Let's say, it is good my CO2 sensor has a range from 400-5000 ppm, since it can spike over 2000 ppm in no-time.
Amazing, this sensor can detect the change even though the oxygen consumption is in the kitchen... :shock:

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Re: Sensair S8

#13 Post by TD-er » 20 Sep 2017, 12:24

manjh wrote:
18 Sep 2017, 17:28
TD-er wrote:
18 Sep 2017, 13:13
I also noticed the CO2 level to rise dramatically fast when cooking (on gas).
Our kitchen has no door to the living room, so concentration becomes equal in those rooms. (12 + 25 + 10 m^2 in total)
Let's say, it is good my CO2 sensor has a range from 400-5000 ppm, since it can spike over 2000 ppm in no-time.
Amazing, this sensor can detect the change even though the oxygen consumption is in the kitchen... :shock:
Well the rooms are connected, so the concentration will become equal in all adjacent rooms.
But it was an eye-opener for me to see this dramatic increase happening so quickly.

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Re: Sensair S8

#14 Post by grovkillen » 20 Sep 2017, 12:36

TD-er wrote:
20 Sep 2017, 12:24
manjh wrote:
18 Sep 2017, 17:28
TD-er wrote:
18 Sep 2017, 13:13
I also noticed the CO2 level to rise dramatically fast when cooking (on gas).
Our kitchen has no door to the living room, so concentration becomes equal in those rooms. (12 + 25 + 10 m^2 in total)
Let's say, it is good my CO2 sensor has a range from 400-5000 ppm, since it can spike over 2000 ppm in no-time.
Amazing, this sensor can detect the change even though the oxygen consumption is in the kitchen... :shock:
Well the rooms are connected, so the concentration will become equal in all adjacent rooms.
But it was an eye-opener for me to see this dramatic increase happening so quickly.
Yes you can even measure the CO2 level in water since equilibrium will happen after a while. The smaller air volume the faster this equilibrium take form.
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Re: Sensair S8

#15 Post by Drum » 21 Sep 2017, 00:26

Hmmmm maybe another way to measure CO2 in an aquarium....

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Re: Sensair S8

#16 Post by manjh » 21 Sep 2017, 11:55

Drum wrote:
21 Sep 2017, 00:26
Hmmmm maybe another way to measure CO2 in an aquarium....
I think you could, as long as the sensor is not submerged in the water. But measuring the CO2 level just above the water, just under light hood covering the tank. It should give a fair indication of CO2 level in the water, I think.
This could be a nice experiment! Measure the CO2 level with and without the air pump switched on!
But I don't have a fish tank... :oops:

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Re: Sensair S8

#17 Post by Drum » 21 Sep 2017, 20:47

I have a big aquarium, with a CO2 system, I do not have the senseair sensor, yet. I will look at the datasheet and see how sensitive it is to moisture.

If it will work, I think putting it in a plastic container upside down would be ideal, if it can handle the moisture. Will be 100% humidity all the time, but I think I can protect it from splashes and immersion. Just in the hood is not enough it needs to be in the water, or in an air bubble in the water.

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Re: Sensair S8

#18 Post by grovkillen » 21 Sep 2017, 21:11

You can protect it somewhat using rice or moisture capturing bags (found in some shoes and purces and stuff).
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Re: Sensair S8

#19 Post by manjh » 21 Sep 2017, 22:23

grovkillen wrote:
21 Sep 2017, 21:11
You can protect it somewhat using rice or moisture capturing bags (found in some shoes and purces and stuff).
You would have to replace that every once in a while. I use a moisture-eating powder sold in DIY stores, it is sold to keep moisture out of campers and caravans. But that stuff takes up moisture and turns into liquid. Can't use it for the fishtank, I don't think the fish would appreciate it very much :shock:

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Re: Sensair S8

#20 Post by Drum » 21 Sep 2017, 23:40

The specs say 85% humidity (NON-Condensing) max. No easy way to do that for an aquarium application.

Using chemical dehumidifiers would be very bad. Ph would go through the roof as would the hardness. I think they are generally calcium based. Calcium chloride if I remember correctly.

On a similar note, I was using a bme280 (pressure, temperature and humidity) sensor in the garden for a few months. It was in a sensor housing which keeps the rain out but allows air flow.
It stopped working so I took a look today. Lots of corrosion on the sensor board. I cleaned it up, put a conformational coating on it and put it back out. Hopefully it will be okay for a while.
Condensation is not good for circiut boards.

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Re: Sensair S8

#21 Post by grovkillen » 22 Sep 2017, 07:46

Yes, I only gave some suggestions to try. They might not work well for aquarium... :roll:
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Re: Sensair S8

#22 Post by Shardan » 22 Sep 2017, 13:04

i have developed electronics for fish tanks for a decade.

For using thks sensor as a co2 sensor it needs a closed chamber to isolate an air "bubble" from the environment around.
If you want to give it a try i'd suggest to use a plastic case, one side open.
Mount the sensor deep inside the case, use silicon or similiar to make the cabling air tight.
Place the box with the open side down over the water surface.
Lower it until the lower rim is below the water surface.

This creates an isolated air chamber, avoiding the influence of the air around..

Anyways, this sensor might be not suitable for this purpose.
The humidity is extremely high and might condense water inside the sensor.
I'd prefer a pH electrode as it is made for working in the water and
calibration is much easier.

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Re: Sensair S8

#23 Post by manjh » 12 Sep 2018, 16:51

I've been running an S8 in a multi-sensor box for a while now. The box contains a dustsensor, a BME280, and of course the S8 sensor.
On the outside I mounted an OLED display onwhich I can show all measured values. Additionally there is an RGB LED that I can give a color to match air quality.
To ensure good readouts, I mounted a small fan.

All very nice, but my wife did not appreciate this humming box displaying text and colors, so I decided it was time for a second sensor.
This time I decided to keep it small: a D1 mini, with the S8 piggy-backed on it.
WIring is very simple, connect to gnd and 5V. On the other side use two 47 Ohm resistors with some crimp around the leads, to connect the signal from the S8 to D7 and D8.
I used a small piece of double sided tape to connect the two, but just to make sure I put a small tiewrap around it.
The whole thing is USB powered, and very small.


IMG_20180912_164008.jpg
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Makes me wonder if there is a possibility to run this off a battery? I know the ESP can, bring it to sleep and wake up every 15 minutes or so.
But what about the S8? If I use three AA batteries, is the voltage too low? What if I connect to a 9V battery?

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Re: Sensair S8

#24 Post by grovkillen » 12 Sep 2018, 17:11

You could try powering it with 4.5V and see. No harm done. 8-)
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Re: Sensair S8

#25 Post by manjh » 12 Sep 2018, 19:00

grovkillen wrote:
12 Sep 2018, 17:11
You could try powering it with 4.5V and see. No harm done. 8-)
Yes, agree. but I thought I would probably not be the first person to think of this, so I was looking for some shared experience.... ;)

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Re: Sensair S8

#26 Post by grovkillen » 12 Sep 2018, 19:03

manjh wrote:
12 Sep 2018, 19:00
grovkillen wrote:
12 Sep 2018, 17:11
You could try powering it with 4.5V and see. No harm done. 8-)
Yes, agree. but I thought I would probably not be the first person to think of this, so I was looking for some shared experience.... ;)
I will test tomorrow at work ;)
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Re: Sensair S8

#27 Post by TD-er » 12 Sep 2018, 21:22

Those CO2 sensors need quite a lot of current to work.
So maybe a battery alone will not work for long because of the relative high internal resistance of the battery.
I guess adding a big capacitor, with a resistor between capacitor and battery, may help here.

Those super caps (0.47F, 5.5V) may be suitable. Just make sure the voltage over the capacitor never exceeds the rated voltage and better stay a bit below it.
If the S8 works fine on 4.5V, then that would be a nice max. voltage.
Just use something like 10 Ohm resistor to charge the capacitor and connect the S8 directly to the cap.

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Re: Sensair S8

#28 Post by manjh » 12 Sep 2018, 23:16

TD-er wrote:
12 Sep 2018, 21:22
Those CO2 sensors need quite a lot of current to work.
So maybe a battery alone will not work for long because of the relative high internal resistance of the battery.
I guess adding a big capacitor, with a resistor between capacitor and battery, may help here.

Those super caps (0.47F, 5.5V) may be suitable. Just make sure the voltage over the capacitor never exceeds the rated voltage and better stay a bit below it.
If the S8 works fine on 4.5V, then that would be a nice max. voltage.
Just use something like 10 Ohm resistor to charge the capacitor and connect the S8 directly to the cap.
Would this work?
https://www.aliexpress.com/item/2-Pcs-U ... autifyAB=0

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Re: Sensair S8

#29 Post by TD-er » 13 Sep 2018, 01:08

Yep, given that Grovkillen can confirm the sensor works fine @4.5V.
And you really have to make sure you do not overcharge those caps to a higher voltage.
They contain a lot of energy in a very small package and higher voltage will destroy them. The only question is, how explosive will the destruction be.

And if you do not supply a charging resistor, these caps will just short circuit the power supply feeding them.
The time to charge them is depending on R*C. (about 4*RC for 80% charge?)
Charging a capacitor means the voltage will increase, so 80% charge means 80% of the charging voltage.
And if you wait long enough, the voltage over the capacitor is the charging voltage, so do not charge with more than about 4.5V
You could go up-to 5.5V, but those caps are actually 2 caps of 2.7V each and if they are not matched very well, the voltage over one may be higher than the other and thus get over 2.7V when you use > 5V charging voltage.

You could also use a switching voltage regulator powered by the cap, but that will introduce unneeded noise on the power lines and inefficiency.
Or just use one of those buck converters directly powered by the battery, just to make sure you can still get enough power when the battery gets discharged.
But that will also discharge the battery to almost 0 and some chargeable batteries don't like that.

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Re: Sensair S8

#30 Post by Drum » 13 Sep 2018, 12:53

I would get the deepsleep and settings configured and working perfect on mains before trying battery power. Less variables to troubleshoot makes life easier.

One thing I saw on the date sheet was "Response time - 2 minutes by 90%"
Grovkillen, could you explain what this means and do you know how long it is from power on to stable readings? Not all devices give a good reading for a short period but as I do not have a S8 I have no idea. I run a few solar / 18650 battery operated units (temperature and battery Voltage mostly), but they are on for a few seconds every 10 minutes and can pretty much run indefinitely with a small solar cell charging the battery.

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Re: Sensair S8

#31 Post by grovkillen » 13 Sep 2018, 15:05

The sensors are working at 4.5V, that is confirmed. :)

Regarding the "2 minutes to 90%" is in fact the response time for first "good" measure. The detector temperature need a certain time to reach a good level and after 2 minutes it has reached 90% of that level, at that point the readings are very much reasonable. You can of course turn the S8 off in between and have the detector reaching this level faster upon next start but this is not recommended since the S8 is only dumping it's values to its EEPROM once every 4 hours. If turned off before this period no records are saved and the ABC will never kick in. The LP8 is better suited for battery powered applications since it's designed to save it's values in between measure and power off.
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Re: Sensair S8

#32 Post by manjh » 13 Sep 2018, 16:08

grovkillen wrote:
13 Sep 2018, 15:05
The sensors are working at 4.5V, that is confirmed. :)

Regarding the "2 minutes to 90%" is in fact the response time for first "good" measure. The detector temperature need a certain time to reach a good level and after 2 minutes it has reached 90% of that level, at that point the readings are very much reasonable. You can of course turn the S8 off in between and have the detector reaching this level faster upon next start but this is not recommended since the S8 is only dumping it's values to its EEPROM once every 4 hours. If turned off before this period no records are saved and the ABC will never kick in. The LP8 is better suited for battery powered applications since it's designed to save it's values in between measure and power off.
Effectively this means the S8 should be powered on constantly, and this kinda rules out battery operation. Switching the ESP off and keeping the S8 on will save some power, but I don't think it will suffice to run on AA batteries for a longer period of time.
Will be looking at the LP8.

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Re: Sensair S8

#33 Post by HomeJCL » 14 Sep 2018, 15:27

"Regarding the "2 minutes to 90%" is in fact the response time for first "good" measure"

Shouldn't this be read as : the usual std for instruments being that it would take 2 minutes before reaching a response step of 90% on the output/measurement ?
This is usually expressed as T90 = 2 minutes, e.g.: if CO2 value in the atmosphere goes from 1000ppm to 2000ppm after 2 minutes it would have a measured valued at the output of the S8 of +/- 1800 ppm ?

On the other hand 2' response step for an NDIR would be very long ...

Of course I'm not intimate with the S8 :D

PS: Warmup would better describe the process :roll:
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Re: Sensair S8

#34 Post by grovkillen » 14 Sep 2018, 15:37

HomeJCL wrote:
14 Sep 2018, 15:27
"Regarding the "2 minutes to 90%" is in fact the response time for first "good" measure"

Shouldn't this be read as : the usual std for instruments being that it would take 2 minutes before reaching a response step of 90% on the output/measurement ?
This is usually expressed as T90 = 2 minutes, e.g.: if CO2 value in the atmosphere goes from 1000ppm to 2000ppm after 2 minutes it would have a measured valued at the output of the S8 of +/- 1800 ppm ?

On the other hand 2' response step for an NDIR would be very long ...

Of course I'm not intimate with the S8 :D

PS: Warmup would better describe the process :roll:
Warmup, that's better! :P
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HomeJCL
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Posts: 46
Joined: 03 Feb 2018, 10:42

Re: Sensair S8

#35 Post by HomeJCL » 15 Sep 2018, 20:07

I’m warming to ESP Easy :twisted:
Belgium and land of ESP ... counting :D

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