|Product Performed to Expectations:||10|
|Specifications were sufficient to design with:||10|
|Demo Software was of good quality:||10|
|Product was easy to use:||10|
|Support materials were available:||9|
|The price to performance ratio was good:||10|
|TotalScore:||59 / 60|
This road test is of great interest to me both personally and work related. On the personal side I suffer from allergies to lots of airborne particulates and have long been searching for methods to measure the particulates in the air so I can better correlate the symptoms with the ambient conditions.
For example I want to know:
This kit seems like a low cost way to start exploring some of these objectives, and this road test is a great way to get a feel for the capabilities of the sensors in the kit.
I want to start by saying the kit surprised me during initial testing - in a positive way. It showed that the small studio where I was shooting video for the road test had poor ventilation and could easily build up concentrations of CO2. I initially assumed the sensor was out of calibration as you will see in the video, but eventually I realized it was indicating a real problem. An air quality audit of that room was not even something I was planning to do. Now I'm thinking about how to set up a fan to achieve better ventilation in that room. And I am adding air quality auditing to my list of uses for this kit.
The air quality kit includes a well-chosen suite of sensors that would be used in comprehensive monitoring and analysis of air quality and comfort levels: CO2, temperature, humidity, smoke particles and dust particles.
High CO2 levels correlate well with humans feeling unwell due to poor air quality.
Temperature and humidity definitely play a role in our comfort levels.
Smoke can be unpleasant or worse.
Dust and pollen can cause allergy symptoms.
The Sensor Evaluation System supplied by the Amphenol Advanced Sensors Group kit is a complete system that includes fully integrated hardware - sensors, MCU and display. The kit includes everything needed to test the sensors, except a power supply, but it can be plugged into any USB port to obtain power.
The arduino UNO also comes pre-loaded with demonstration firmware so here is a video that shows how the kit is assembled and what it does when power is applied.
Assembly & Power Up Test Video
There were a couple of things that surprised me with this kit:
The first surprise is that hardware kit is a complete system that just plugs together and it includes an OLED display. In fact the main micro controller card, sensor interface card and OLED display arrived already plugged together, only the sensors had to be plugged in.
The second surprise is that fully functional software comes pre-loaded on the host micro controller. Surprising because it is a 3rd party micro controller card. This software reads all the sensors and displays their values on the display.
So overall, the system was amazingly easy to set up and start taking readings.
Next up are descriptions of each sensor and videos of each of the sensors in action:
Carbon Dioxide Sensor
CO2 sensors are often used to monitor air quality. CO2 concentration level in an inhabited space is a very good indicator of other toxins that build up when there is inadequate ventilation. High concentrations of CO2 also correlate to low oxygen levels, but in situations where low oxygen can be a problem, an oxygen sensor should be used.
This sensor uses NDIR (non-dispersive irfrared) CO2 sensing technology. The basic principle is based on the fact that CO2 absorbs light at a wavelength of 4.26 um. Generally an IR source at this wavelength is used to illuminate a controlled flow of air. An optical bandpass filter at this wavelength is inserted before an IR detector opposite the source. CO2 concentration is proportional to how much light reaches the detector.
The T6713 can measure CO2 up to 5000 ppm. +/- 25 ppm up to 2000 ppm and +/- 30 ppm between 2000 and 5000 ppm. This is very good performance.
It has <2% stability variation over 15 years, so it lasts a very long time.
This CO2 sensor runs off 5V and can use an I2C interface or a UART interface. It also has a PWM output.
There is an internal 1M pull-up on the Control Pin which puts the device into UART mode at 19200 Baud. If this pin is grounded, the device is placed into I2C slave mode, which is the case for the sensor evaluation shield in this kit. The T6713 sensor uses the Modbus protocol but wraps it in an I2C format.
My continuity tests show the evaluation shield makes the following connections between the CO2 sensor and the UNO:
|Sensor PIN||Description||UNO Pin|
|1||TX / SDA||SDA|
|2||RX / SCL||SCL|
|6||CTRL / Test||GND|
Amphenol supplies an app note for this sensor here.
Here is a table that shows the symptoms associated with various levels of CO2:
|350 - 400||Background (normal) outdoor air level|
|400 - 1,000||Typical level found in occupied spaces with optimal air exchange|
|1,000 - 2,000||Level associated with complaints of drowsiness and poor air|
|2,000 - 5,000||Level associated with headaches, sleepiness, and stagnant, stale, stuffy air. Poor concentration, loss of attention, increased heart rate, and slight nausea may be present.|
|>5,000||This indicates unusual air conditions where high levels of other gases could also be present. Toxicity or oxygen deprivation could occur. This is the permissible exposure limit for daily workplace exposures.|
My studio had levels over 1,700 ppm - not a great situation, but very good to know. That measurement alone was worth the price of admission.
Here is a video showing the CO2 sensor in action:
Temperature and Humidity Sensors
Temperature and humidity are very important for human comfort, but also for all manner of manufactured products, materials and processes. Consequently temperature and humidity sensors are very common and definitely used to monitor air quality. The T9602 includes both a temperature sensor and a humidity sensor in one module. They have several features that I really like and that set them apart form other sensors:
Other features include flexible interfacing (either I2C or pulse density modulation) This kit uses I2C.
This device runs off 3.3 V although a 5V variant is available (it looks like there is some level conversion for the I2C on the evaluation shield so it plays nicely with the 5V devices on the same bus)
Here is a video showing both temperature and humidity sensors in action:
Here is the connector pinout - there is some circuitry between the sensor and the UNO for level translation:
|T9602 Pin||Function||UNO Pin|
Smart Dust and Smoke Sensor
The SM-PWM-01C Smart Dust Sensor detects dust particle concentration in air by detecting infrared light reflected from dust particles. Air is moved through the module by thermal expansion. It looks like the resistor that is visible in the image above is used as a heater which heats air, causing it to rise. The slot over the resistor is the inlet port and the smaller slot on the far side of the module is the outlet port. This implies the device should be oriented with the outlet port above the inlet port. The semi-circular port allows the detector lens to be cleaned. It should be covered with opaque tape when the device is properly oriented with the outlet port above the inlet port. The application note mentions using black sponge to avoid reflections, although I don't recall seeing any in my kit. (When I opened the package I wasn't looking for it)
If I am reading the app note correctly the number of reflections off dust particles is proportional to particle concentration and the duration of the reflections provides a measure of particle size.
The output pulses (presumably frequency) on P1 are proportional to particle concentration of small particles in the 1-2 um range, such as smoke.
The output pulses (presumably frequency) on P2 are proportional to particle concentration of larger particles in the 3-10 um range, such as dust and pollen.
These signals should use a 30 second moving average to obtain stable readings.
This is a 20 um Ragweed pollen (it can range in size - some are much smaller):
I'm a bit hazy on exactly how the reflection signal is converted into P1 and P2 pulse signals - the explanation in the app note tries to simplify it to a 2-dimensional geometry, but I think I would need to know more about the optical geometry to understand it fully.
Ragweed season is rapidly approaching, so I should be able to see if it is detectable.
Here is a video of the smoke sensor in action:
Here is the dust sensor connector pinout:
|SM-PWM-01C Pin||Function||UNO Pin|
Other significant components in the kit include:
An AAS Arduino UNO (ASS-AQS-UNO)
The MCU provided with the kit is a standard Arduino UNO in most respects but it is branded as AAS (Amphenol Advanced Sensors) and it comes with a pre-loaded air quality demo program.
This makes working with the evaluation kit super easy, allowing more focus to be on sensors and data than getting an MCU to work. Presumably I can try flashing the code available on GitHub onto a standard UNO to see if it works before editing the code or erasing the original demo. (there are several versions available on GitHub)
Note that the dust sensor pulse signals require a pin change interrupt library.
One thing I want to try is to see if I can split P1 and P2 signals into separate readings.
Another thing I want to explore is sending data out via Bluetooth.
If and when I attempt these enhancements, I will update this road test.
An AAS Sensor Evaluation Shield (AAS-AQS-UNO)
The AAS Sensor Shield breaks out the UNO signals to sensor-specific connectors, making the whole system plug-and-play. There are a couple of transistors to make I2C work with a 3.3 volt device. There are also some extra connectors including Bluetooth and VOC sensor (volatile organic compounds).
This card can plug onto any Arduino UNO compatible connector MCU which means it should work fine with many MCU cards from various manufacturers.
An OLED display
The included display is a 96 x 64 monochrome OLED. (cyan)
It runs off 5 volts and uses I2C for communication.
AS you can see in the above videos it does a nice job of displaying sensor data.
Here are the pin connections to the UNO:
|OLED Pin||Funtion||UNO Pin|
This display is fairly generic, which is useful - it looks like the AdaFruit Arduino library for a 96x64 OLED would work with it.
There is a Bluetooth connector on the sensor shield, but I couldn't find any info about it anywhere. I mapped the pinout below:
|Bluetooth Connector||Function||UNO Pin|
This would seem to indicate the Bluetooth port would use a bit-banging serial protocol, probably emulating a UART and SPP over Bluetooth.
Hopefully I will be able to find out more about it and try a remote application.
Here is a brief video about it:
I think this product has a lot of potential - it is quite unique in the performance it achieves at this price point.
The sensors are very accurate and pre-calibrated and the combination of sensors is very useful.
The kit was complete incredibly easy to use. At first I was a bit worried that there would be nothing to write about - just plug it in and it works.
I learned quite a bit during this road test including how the various sensor technologies worked.
Between what I learned and the use I'm getting out of the system, this road test has been worth all the work and I'm very glad I got involved..
The Amphenol Advanced Sensors division has put together an excellent sensors kit, well suited to its purpose of air quality measurement.
I expect to continue working with this kit and I will update this road test as I progress.
I will add a battery and package the system in a 3D printed case as soon as I get my 3D printer overhauled.
I will be taking readings during allergy season to see how weather affect readings and how filters affect readings.
I will keep looking into wireless operation.
Right now the system is great for auditing air quality and it could be set up to continuously monitor air quality, but I want to eventually find a use case where it improves my quality of life in handling allergies better.
I have been thinking about how to design a package for this system for quite a while. The sensors and display are mounted in very awkward locations, given that they all need access to ambient air. A rectangular box would block all functionality of the system, so I eventually decided the case had to be divided into 3 main sections plus a bezel for the display.
The resulting design was still complicated due to all the irregular shapes that needed to be enclosed or accessed. The case was 3D printed in black, which doesn't photograph very well, so the first video is animations of the CAD design:
The next video shows the actual 3D printed parts and the completed assembly:
The design took a long time (pondering off and on) because it was difficult to come up with a design strategy that I felt would be efficient and workable. The final assembly took 9 screws, which is more tapping than I would like, but it ended up to be very solid and quite functional. As hard as this was, I can't imagine how I would even do it without a 3D printer.
I will likely add in some measurement results if they yield anything interesting.
Some of the enclosed spaces I intend to test for CO2 buildup are:
Links to Relevant Material: