This is critical to the device. A few choices are:
- Plantower PMS5003, PMS7003 - compact and low noise, suitable for indoor application, $15-17$
- Nova Fitness SDS011 - larger size, slightly stronger fan, $15-$17
- Sensirion SPS30 - seems working fine, good brand-name, ~30$
- Winsen ZH03B, similar to PMS5003, $20
I would discourage
some sensors because of my experience working with them:
- A cheapter one such as Shinyei PPD42NS, Samyoung DSM501A, 5-7$. I have not get a stable reading plus you need to have fan installed if no active flow of air is presented
- Alphasense such as N3 and R1: the readings is not consistent between units and expensive
- Honeywell HPMA: I bought 3 units from Aliexpress, and they are dead after 5day to ~5 months in use
- Arduino: this option is popular before 2015, and it would work with this project + low power consumption
- ESP8266/ESP32: it provides more power, more RAM, WiFi-connected
3. Power management:
- A lithium charger and protection board, such as TP4056
- 5V boost for PMS7003
- I used a charging board with 5V boost converter using IP5306. The drawback is the chip needs at least 50mA to stay on
- Any LED such as RBG led or WS2812 would works
- Better yet, use OLED 128x32 display, so we can write out concentration, time, and battery voltage
2.2 Wiring and gluing
Below are the wiring diagram. The diagram are not contained a wire to manually turn IP5036 boost, and 220ohm "dummy" load, so that the boost "seeing" enough current to keep on.
In addition, I wired up pin D7 (on WeMOS) to pin Key (on IP5306) with 1000ohm resistor to turn on the 5V-boost converter. If you have other loads around a few hundreds mA, the IP5306 should turn on automatically, and turn on via D7 is not needed. The datasheet indicated as lead 50mA, but I found it needed more than that. With PMS7003 and OLED running on 5V boost, it is not enough to keep the boost converter turn on. I add a 220ohm resistor between 5V and GND plus PMS7003 and OLED to keep it on.
Grasp some tools to works with the box, cut the wire, and stick parts together.
And here are the parts.
Inside the box
If you want to know more about specification of dust sensors, visit Table 1 in this post. Let continue next page with the code.