Does anyone have a intrest in a cheap CO2, temperature, humidity sensor with LCD?

**DDG** · 19-05-18, 08:48 PM

Hello.

I know a lot more about electronics than I do about horticulture and I am currently planning a project for building a DIY CO² sensor, it would have to be classed as a advanced DIY project, but the cost of a humidity and temperature sensor is so low that I might as well throw those in while making the CO² sensor/read-out system.

[This was written last, but I wonder if anyone know of any system that would allow CO² dispensers to be opened/closed electronically because it just occurred to me that what I have planes for could be turned into a low-cost CO² system assuming a fitting release is available to be used, if a suitable control mechanism for the valve exists and doen't need to be created from scratch then it would be fairly easy to implement. But the safety features would have to be thought about hard and long to ensure it is safe to use.]

If I would make one for just me it would take one form which isn't useful to others, but I wanted to check if there is any interest in this sort of thing because then I would make a design to be sent to others, I wouldn't charge any money, not more than a couple of % of the total cost(the shipping cost for the components to me would be shared and then you would pay for the shipping home to you) of the supplies(to make sure I don't loose money on the hole thing in the end) since this isn't about making money but rather to offer something to this community. And even if you aren't adding CO² to your grow room I for one think that it would be very interesting to get a read-out of the ppm's(parts-per-million's) of CO² in your grow room. I don't add any CO² but I still want to know how much I got for my plant but I am not prepared to pay for a commercial solution.

The cost of this device would be dominated by the cost of the CO² sensor but I've made an estimate for the cost and permitting £20 to "Misc" stuff like plastic or 3D printed enclosure the estimate cost is £43,5 but please note that this estimate is based upon buying single items, if bought more, then it would be cheaper and if lower accuracy would be acceptable then the cost can be cut further. But for an estimated £43,5 we would get these specifications(the price wouldn't change much by removing the humidity and temperature sensing):

Relative Humidity(RH) range: 1% - 99%
Relative Humidity(RH) accuracy: +/- 1%
Temperature range: -40°C - +125°C
Temperature accuracy: +/- 0.25°C
CO² range: **see below
CO² accuracy: Not specified

**The choice of CO² sensor makes a big difference and price is a important aspect, there appears to be sensors that cost around £15(might be £23, the market for these sensors are confusing to say the least) but that gives a sensor with a range of 400ppm - 10000ppm, or a sensor with 0ppm - 5000ppm, or 0ppm - 2000ppm. If one would double that price then the range would be 0ppm - 10000ppm. As for the accuracy of these sensors very little info is found but I am not the first one to build a sensor with these, there are also a difference between a CO² sensor and a Volatile Organic Compounds sensor which calculates an equivalent CO² value which appears to be just as good.

This device would consist of a OLED or LCD display panel which sits in a little plastic box or maybe on a circuit board made to be mounted onto a panel or may both so one may choose, in any case that box would have a battery which would be required to be changed but given today's circuitry the battery should last a long time, a battery that can be charged from a USB port could be done but then it would have become a complete product and i don't think it is viable for me to dedicate all that time without the intention of making a profit on these things. There would however be a option of a external power supply if you had one at hand with a suitable output voltage.
And of course there would be a cable running from the box to the plastic casings probe which would be hung inside the grow room. My estimation of cost was based on the assumption that the user would supply a couple of AAA batteries or something like that.

So the conclusion is I guess this, are there any interest from the members here for a below £60 CO², Relative Humidity and temperature measurement device with a OLED/LCD display for reading out the values?

If there are any people out there for whom this sounds intriguing then please let me know, and if so I'd also like to know if you would prefer a more DIY style "product" for a lower cost or a more complete and professional look to it for a higher cost?

To be clear about my intentions, if there are enough interest then I would be glad to work this out and sooner or later I would be able to supply people with this sensor device, if there aren't enough interest then I will probably just throw together my own 1-time DIY contraption and share the details of how I did that.

I hope you all are having a nice weekend.