Small wall outlet sensor node
I've created this to have easiest way to establish environment monitoring across the house
the idea is to have a wall outlet type plug with everything on board
and I like to do small things
The board is less than 50 x 50 mm
It contains AC-DC power supply with resettable fuse, 3.3V LDO, arduino based on atmega328, radio, LED, and two slots, one for DS18B20 and the second one is for DHT11/DHT22
The real consumption measured by RMS wattmeter is just 0.3W
I guess the DHT11/22 pin could also be used for PIR sensor or drive a relay/actuator.
@axillent, did you get a chance to test the MPL-03S-05E I sent you?
@axillent Very nice! How do you make the circuit board and the soldering of surface mounted components is quit advanced.
@gregl thanks, yes, the same board can be used for any simple 1-2 inputs or 1-2 channel actuator
I have a plan to create something similar for wall switch in 3-wire and 2-wire versions
I read a datasheet and I doubt about where to use it
it requires quite a big external filter
the total size will be bigger than normal isolated AC-DC
The supply based on none-isoleted schema is interested in some projects where you need lower footprint.
If someone interested I will do a test
Here are a schematic and PCB prints
it is half-a-day project including a home-production of the PCB
but it is a 2-year experience
I also use a simplified approach for some PCBs, without drilling, using 0.5mm FR4 cut by office scissors and thermo-transfer technology. This one requires about 30-50 minutes for the production circle.depending on etching speed. For example this two side AC lamp off-timer:
Pictures bellow are virtual, under printing
It would be cool with a 90degree angled version as well
@axillent Your an evil genius!
all this is simple, just a patient work
Printed thing is a bit ugly comparing to the virtual one, but it's work is real
Small wall mysensor.org node – 00:10
@axillent So very very cool!!
as @gadu commented, making one at 90 deg so its very low profile would be even better for places such as hallways where the sensor could be bumped....
@axillent - well done!
@axillent Very impressive! What is the total cost of the components involved?
@bjornhallberg it is hard to say
the BOM is simple and short
but the cost of a single component is dramatically depends on how many your purchase in a single order
for example atmega328 purchased in 10pcs will be US1.2 pcs while a single pcs will costs US3-4
If it will be an interest I think in production this PCB can cost retail US8-12
very very cool!!
made two more with modified box - it is a bit wider to hold DHT sensor inside
I made a new sketch as a combination of Dalas example and DHT. This new sketch able to detect automatically connected sensors and work according to detection.
One problem I've got. I cannot get DHT working from AC plug. It is working fine been powered from DC and failed during startup been powered from AC The most probably the reason is high pulsation (up to 440mV) coming from the supply based on SR10 chip.
Dalas is fine with this but not DHT. Probably some code inside the library holds.
Had to mark each sensor with radio channel because they will work with different gateways