Dyson DP04 teardown (fan/filter) - Page 1
Forum section: electronics / general

author: thmjpr
author_rank: Regular Contributor
timestamp: March 05, 2020, 07:11:12 am
content: Dyson DP04 fan with filter in the base (under that gray grille).Has particulate matter sensing, VOC, NO2, humidity, temperature, wifi.Front with the cover off showing the LCD display. There is an ambient light sensor which adjusts the brightness, so no light pollution at night. Looks like its on the right hand side with that infrared receiver. I'm not entirely sure how it gets through the opaque plastic case though. Only the LCD cover is clear.Interesting nose cone design in the middle.Big wifi module (wurth) and sensors are off to the left.Back of the main board,STM32F429running the show.The connector (J3) on the top left goes up to the top air guide, then to a small motor that opens or closes vanes on the air guide. When the vanes are open the air directs outwards instead of forward. The TI chip beside the connector is ULN2803A (0.5A transistor array).View of all the sensors.The large silver box in the middle is the PlantowerPMS5003. Its a $20-30 sensor, so none of those cheap $2 infrared LED based ones. Can differentiate PM2.5 (smoke) and PM10 (dust, pollen) particulate matter.I've used a similar part in my air quality monitor:https://hackaday.io/project/21912-portable-air-quality-monitor, its decent given the compact size.Note that the PM sensor has its own internal fan, which ducts directly from outside and circulates around the various sensing boards. Its not possible to use the units main fan as it would result in varying air flow when you change its speed. Its also necessary to sense ambient air, so you can't sample from inside of the unit post-filter.SHT31humidity and temperature sensor.Unknown sensor in the middle, no markings on it, I expect this is for VOC/NO2. Initially I thought it could be temperature, as they snaked the PCB a bit, but the SHT31 already has that. Maybe it has an internal heater that they want to isolate.

author: thmjpr
author_rank: Regular Contributor
timestamp: March 05, 2020, 07:13:47 am
content: Base of the unit, top is the power inlet board, fairly standard. I didn't check why it has three wires yet, maybe a standby power? The plugpack is 2-pin so its not earthed.In the middle.. is just insane, three bearings to guide the cable as the base rotates (the fan can swivel 180 degrees back and forth). The wire barely touches one of the bearings in normal use, they are completely unnecessary as far as I can tell.This is the other side of that base plate above. In the middle you can see a hole for the bearing.Outside of that, a number of small magnets so the fan will not freely rotate, it will "snap" into various positions.Outside of geared ring you can see a striped surface, is is for a photo-interrupter so it can determine its current location (once it moves a bit and scans a code).The white ring with the tabs is another bearing race for vertical force, this one has some plastic balls inside.Image of the fan blades, plastic material.Top and bottom of the fan motor control board, STM32.

author: Gyro
author_rank: Super Contributor
timestamp: March 05, 2020, 08:04:24 pm
content: All that complexity for a fan!I wonder how efficient it is at actually filtering the air, given that most of the airflow is drawn directly through the back of the hoop by the 'air multiplier technology' (venturi effect).

author: thmjpr
author_rank: Regular Contributor
timestamp: March 06, 2020, 04:13:28 am
content: Measured the three pins on DC plug: 20.5V, 19.5V and gnd. Its still possible to be some form of low power standby trigger I think.Power consumption:- Plugpack only: 0W (20mA 0.05 PF, not enough resolution on meter)- Unit off: 2W- Fan low (1): 3.6W- Fan mid (5): 8.6W- Fan high (10): 40WI typically use 2-3 fan speed so power consumption is very low. Of course its not going to filter much air at that speed, but thats ok here.Quote from: Gyro on March 05, 2020, 08:04:24 pmThat is a good point, when its in "fan" mode you'll get say half the air being room air and half coming from the filter. If you expect the air in your room to circulate eventually, its not the end of the world, but if you were working on something dusty it would not be pleasant. When its in "vane closed" mode, there is no venturi effect and the air will come directly from the filter only.