- Introduction
- Printing the parts
- Assembly
- Flashing the firmware
- Configuration
- Registration
- Home Assistant integration
- Mounting instructions
- Troubleshooting
The steps in these introductions are all the steps I needed to create a single enclosure. Feel free to adapt, replace or skip any of the steps, to make your own version.
Some of the photos in this guide are from a prototype version using the Witty Board. While this might look different, all of the steps are quite similar.
You can find the printable files in the 3d folder. The parts do not require special attention. Make sure that you print the parts with the biggest flat surface down. At least 20% infill will ensure they are rigid enough. I used PLA, but since the sensor must not be installed in direct sunlight, I do not expect any problems.
It depends on the use-case if you need all the parts.
You need at least:
- Enclosure bracket
- PCB bracket
- Screw hole covers
- Temperature sensor cover
For usage with a flexible tube:
- Tube bracket
- Tube fixing ring (2x)
For easy drilling of the enclosure:
- Drill templates (top and bottom)
- Rubber seal templates (16 mm and/or 12 mm)
You might need to adapt the tube fixing rings to your particular tube. There might be slight differences in the flexible tube outer diameter. The rings must fit tightly, so they stay in place.
For this step, you will need:
- 4-pin 2.54 mm male header
- 4-pin 2.54 mm male header right angled
- 4-pin 2.54 mm female Dupont headers (2x) with terminal pins (8x)
- JST terminal pins (4x)
- Wires (thin, six colors if possible)
- Pliers, crimping tools and wire strippers
Optionally, if you plan to connect to the power line directly:
- 2-pin 2.54 mm female Dupont header with terminal pins (2x)
- 2-pin 2.54 mm male Dupont header with terminal pins (2x, for contra cable)
The sensors can be soldered to the ESP8266, but another option is to create a cable loom and use wire-to-board connectors.
The cable should be assembled as follows (do not solder it to the ESP8266 yet):
You can re-use the JST connector housing that comes with the SDS011 cable.
For this step, you will need:
- Enclosure (Gewiss GW44 205)
- A slow (hand-operated) drill with a 1 - 1.4 mm drill bit
- An electric drill with a 3 mm drill bit
- A 16 mm spade drill bit
- Small piece of scrap wood
- Strong adhesive tape
- Sharp chisel or another deburring tool
The drilling step is a time-consuming step.
Secure the drill templates on the top and bottom side of the enclosure, using some strong adhesive tape. The templates should be centered and tightly mounted to the edge of the enclosure.
The small holes should be drilled carefully. Use a hand-operated drill, because an electric drill will melt the plastic, clogging up the drill and potentially breaking the drill itself.
The bigger holes should be pre-drilled using a 3 mm drill bit first. Use a piece of scrap wood on the back side, so that the drill bit does not shoot through the plastic, potentially damaging the enclosure.
On the bottom side (next to the outtake holes), use the 16 mm spade drill bit to create a hole for the cable gland for the power supply. On the top side, use a 16 mm spade drill bit for the flexible tube as well. Use the piece of scrap wood on the back side of the plastic.
Note: make sure that you hold the enclosure firmly during drilling. If the spade drill bit gets stuck, it might start to rotate the enclosure.
Note: if you plan to directly solder the power supply cable, you can better drill a 12 mm hole on the bottom side.
Clean-up all the holes and remove any of the burrs. This ensures that the rubber seals can be mounted properly. A chisel works great in this case, without scratching the plastic.
For this step, you will need:
- Enclosure bracket
- M3 Brass inserts (5.3 mm outer diameter, 5 mm or 6 mm tall)
- M3 8 mm self-tapping button-head screws (4x)
- An electric drill with a 3 - 4 mm drill bit
- Small piece of scrap wood
- Soldering iron
Drill the enclosure mounting holes first, depending on your desires. If you decide to hang it on two scows, make sure that you drill the two top holes only. Use the scrap piece of wood to ensure that the drill bit does not shoot through the case.
Insert the M3 brass inserts in the three bigger stand-offs on the enclosure bracket. The easiest is to do this with a soldering iron. Make sure that the molten plastic does not get inside the brass insert. One way to do so, is to insert a small M3 bolt first (e.g. 5 mm or 6 mm bolt). If you struggle to get the M3 brass inserts flush due to the molten plastic, you can decide to drill the holes first, so that the molten plastic can get out.
Mount the enclosure bracket next. Use the four M3 self-tapping screws to secure it to the enclosure.
For this step, you will need:
- Cable gland 16 mm (2x) including nut (2x)
- Rubber seal 16 mm (2x)
Note: you can also cut some seals from an old bicycle tire, using the rubber steal template.
Install the cable glands on the top and bottom side. From the inside, put on the rubber seal first and then the nut. Tighten the nut by hand, ensuring that it is as tight as possible. Verify that it will not come loose when you tighten the cable gland itself.
The rubber seal ensures that the cable gland does not get loose and prevents water from coming in.
If you decide to mount the enclosure, now is the time to mount it to its final destination. The enclosure mounting screws will be hard to reach once you finish the next step. To improve water resistance, use a M3 or M4 seal on the inside between the screw and the enclosure.
For this step, you will need:
- M3 15 mm brass stand-offs with 6 mm thread (3x)
- M3 spacer 3 mm (3x)
- M3 10 mm bolt
- ESP8266 (Wemos D1 Mini V3)
- Air quality sensor (SDS011)
- GPS sensor (NEO-6M, NEO-7M or NEO-M8N with the blue PCB and solderable antenna).
- Temperature and humidity sensor (BME-280, 5 V version)
- PCB bracket
- M2 self-taping screws
- Wiring loom, or wires for soldering
- Temperature sensor cover
- Hot glue
Fix the GPS sensor and the ESP8266 on the PCB bracket.
Install the brass stand-offs in the brass inserts in the enclosure bracket. Then place the air quality sensor on top, with the fan down. Then place the PCB bracket on top, using 3 mm spacers. Fix them with the 10 mm M3 bolts.
The BME-280 temperature sensor can be mounted next to the outtake holes, using a small screw. It is recommended to mount the temperature sensor cover as well, to isolate the temperature sensor better from the inside air. A drop of hot glue should keep it in place. I must admit that this sensor cover is an afterthought, to make the temperature readings more accurate.
Finally, connect the wiring loom in accordance with the wiring diagram above. Use the following pinout:
SDS011:
- Pin 1 (TX) -> Pin D1 (GPIO5)
- Pin 2 (RX) -> Pin D2 (GPIO4)
- Pin 3 (GND) -> GND
- Pin 4 (2.5m) -> unused
- Pin 5 (5 V) -> 5 V
- Pin 6 (1m) -> unused
BME-280 (5 V version):
- Pin 1 (VCC) -> 5 V
- Pin 2 (GND) -> GND
- Pin 3 (SCL) -> Pin D4 (GPIO2)
- Pin 4 (SDA) -> Pin D3 (GPIO0)
NEO-6M, NEO-7M or NEO-M8N:
- Pin 1 (VCC) -> 5 V
- Pin 2 (TX) -> Pin D5 (RX)
- Pin 3 (RX) -> Pin D6 (TX)
- Pin 4 (GND) -> GND
For this step, you will need:
- Tube fixing ring (2x)
- Tube bracket
- 15-20 cm flexible tube (6 mm inner diameter, 8 mm outer diameter)
- Power supply cable (e.g. USB cable)
- Zip tie
Insert the flexible tube through the cable gland and connect it to the intake of the air sensor. Install a tube fixing ring on the inside. This ring should prevent water (if any at all) from running down the tube into the sensor. Then install the tube bracket on the cable gland and install the flexible tube to the bracket, with a tube fixing ring on the end.
Install the power supply cable. The USB cable should fit thourgh the 16 mm cable gland. Route it behind the PCB bracket and connect it to the ESP8266. Use zip tie to fix it to the PCB bracket top hole, for additional stress relief.
The cable gland on the bottom should be tightened all the way for the power supply cable. This acts as an additional strain relief. The cable gland one on top should be tightened as well, but not too tight. The flexible tube must not be compressed too much otherwise it could obstruct the air flow. Make sure that if you pull on the tube, it cannot move. Then look down the tube, to see if you do not see any inward affliction of the tube.
The shorter the tube, the better it is. According to the datasheet of the sensor, a tube length up to 1 m is allowed. The original manual suggests the use of a 20 cm tube. The Dutch National Institute for Public Health and the Environment, who are stimulating people to join the Sensor.Community, suggests to use a tube less than 5 cm, to increase plausibility of measurements.
For my design, a tube of approximately 15-20 cm is necessary to create an unobstructed 180 degree bend. Without a tube, it would be hard to ensure that the sensor is mounted upright AND make it water-resistant. It also ensures that the sensor sucks up fresh air (away from the outtake). You can decrease the tube length if you mount the sensor on a dry location (even removing the tube bracket at all).
The tube has a inner diameter of 6 mm (~28 mm² of area), the actual intake port has a diameter of 5 mm (~19 mm² of area). The 85 outtake holes (~96 mm² of area) should allow for an unobstructed air flow. I have compared my sensor with other nearby sensors, and it performs identical.
A more-scientific study observed a decrease in the maximum air flow of the flexible tube, with longer tube lengths. Comparing 20 cm with 100 cm, the air flow decreased linearly from 664 ml/min to 412 ml/min. Every 1 cm of tube would impact the maximum air flow by about 0.5 %. Note that this is the maximum air flow, which may be much higher than the air flow generated by the air quality sensor. More details of this research can be found here.
For this step, you will need:
- The screw hole covers (4x)
- M3 x 7 mm rubber seals (4x)
Last step is to install the lid. The enclosure comes with four screws to close the lid. For additional water proofing, add a M3 rubber seal and finish it off with a screw hole cover.
The screw hole cover can be removed with a large flat head.
Your sensor is now ready for use.
For this step, you will need:
- A micro USB cable
- esptool.py
- Firmware file (see firmware folder.
From the command line, invoke:
esptool.py --port [PORT] write_flash -fm dio 0x00000 latest_en.bin
Replace [PORT] with the serial port of your sensor. It is typically
/dev/tty/tty.USBxyz on Linux and COMn on Windows.
Once flashing is completed, power cycle the sensor.
Power-on the sensor. If it has not been configured before, it will start a wireless network. Connect to this network, and navigate to http://192.168.4.1.
On the configuration page, you can configure the WiFi network to use. It is also possible to configure the hardware and API connections. Some points of attention:
- Make a note of the 7-digit identifier shown in the top bar. You will need this in the next step.
- Enable beta updates. Note that your sensor may seem unresponsive the next time it boots, because it will most likely download the new firmware.
- Enable the Sensor.Community API integration (using HTTPS). Enable others as desired. You do not need to enable any API integrations if you decide to use the local Home Assistant integration.
- Ensure that you enable the right hardware. For this build, enable
- SDS011
- BME280
- GPS (NEO-6M, NEO-7M or NEO-M8N)
If the sensor cannot find the configured wireless network, it will start its own wireless network again. You can then start over.
The WiFi chip and the GPS chip are power-hungry. This results in some heating-up of the enclosure, depending on the exact module used and the amount of WiFi traffic. This will affect the BME280 temperature and humidity readings.
It is possible to account for an offset of the temperature readings in the firmware (this is not possible for humidity, unfortunately). To find the offset, it is possible to run the sensor for some time, without the lid of the enclosure mounted. The graphs below show the offsets for two of my sensors (yellow line is the one without the lid mounted).
The graph show an offset of about 1 °C to 2 °C, and it follows the temperature curve of the enclosure without the lid. Similar results were achieved in different environments.
The NEO-M8N is more-efficient than the NEO-6M or NEO-7M. Using the u-blox configuration tool, it is possible to enable more-efficient power saving modes, at the expense of accuracy (which isn't a problem for a stationary device). Do note that that not all devices have built-in flash for storing configuration parameters, so they might be erased after power cycling. Consult the following sources for more information:
- https://www.u-blox.com/sites/default/files/products/documents/u6-PowerMgt_AppNote_%28GPS.G6-X-10014%29.pdf
- https://www.u-blox.com/sites/default/files/products/documents/PowerManagement_AppNote_%28UBX-13005162%29.pdf
If you decide to contribute to Sensor.Community, you can go to https://devices.sensor.community/ to create an account.
Once you have created an account, you can add sensors using the sensor identifier from the previous step. An important note here is that you cannot modify an existing sensor, and if you delete it, you cannot register it again. Make sure that you add three sensors under the 'Hardware Configuration' section:
- SDS011
- BME280
- GPS-NEO-6M (also for NEO-7M or NEO-M8)
Once your sensor is registered, you can look it up at https://maps.sensor.community/. It might take some time before the first measurements appear.
If you made any mistakes during the registration, please check this for details on how to get support (you will need to send an email and ask them to manually correct the registration).
There are two sensor for Home Assistant available. The first one uses the Sensor.Community API, the other directly talks with the sensor.
- https://www.home-assistant.io/integrations/luftdaten/
- https://github.com/lichtteil/local_luftdaten
After installing the integration per installation instructions, add the
configuration below to your configuration.yaml. Aadapt the IP address to
match your sensor's IP address. The scan interval should not be less than 120
seconds, because the sensor itself does not update faster than that.
sensor:
- platform: local_luftdaten
host: [IP HERE]
scan_interval: 120
name: Air Quality Sensor
monitored_conditions:
- BME280_humidity
- BME280_pressure
- BME280_temperature
- SDS_P1
- SDS_P2Restart Home Assistant, and you should have additional sensors to add to your dashboard.
There are some mounting instructions:
- Mount the sensor upright (tube on top). The sensor requires this position, so that gravity optimizes the flow of particles through the air sensor. It also ensures that water cannot enter the outtake holes on the bottom.
- Make sure that splashing water cannot enter the outtake holes on the bottom.
- The sensor should be mounted in the outside and average environment. This means that you should not place it next to a chimney, for example.
- Ideally, the sensor should be mounted at 1.5 m height. During the registration of the sensor, you can account for other heights.
- Do not mount the sensor in direct sunlight. The temperature sensor might report incorrect measurements.
Finally:
- Inspect the sensor once or twice per year. Check if it is still mounted securely, that there is no dirt inside the sensor and the tube is clean.
- Discoloration due to UV light is to be expected.
Some things to consider when troubleshooting a sensor:
- If you plug in the power, you should hear the fan spin up for a brief period. If it does not turn on, check the connections. If it does not turn off, something might be wrong with the firmware.
- Check the web interface for debug logging and error counters.
- Some ESP8266 boards have on-board USB-to-serial. The firmware will output logging to this port (at 9600 baud).