Arduino Pro Mini + nRF24L01 (jmodule?? or something else)

[gohan]

@martim

this is similar to what was posted above but also with a couple of capacitors: both need to be connected with arduino with jumper cables but it allows to easily swap radio module. Otherwise you have to use something like this or a board like Boots33 posted

[Nca78]

Hello, yes you still need to connect to the nano but it's a bit more convenient because the pins are all in one line and if you are using a 5V arduino the voltage converter is included.

As you might have seen in the jmodule thread I am doing a compact board for pro mini that's a bit bigger in surface (surface of the pro mini + NRF antenna + one optionnal row of connectors that can be cut if not needed) but much thinner and I think easier to solder and with 2 levels of voltage regulation (RAW => Vcc and Vcc => radio).
I have made 2 sensor boards also for temp/hum/light (if you are using i2c sensors only), reed switch and ADXL accelerometers. The sensor boards are made to be powered by CR2032 button cell so if you follow this you will have plenty of room (will make something around 42 * 25 * 12 mm all included).
I'm waiting for the boards to arrive (hoping Fedex will deliver before lunar new year) and after testing (and making the sketches :)) I will publish all the needed info.

To get the PCB you need to order them from a PCB maker (Dirty PCB, Seeed Fusion, Elecrow, PCBWay, ...) using either the gerber files available on openhardware.io website, or by using the links to PCB websites that you find either in the descriptions on openhardware.io or in the threads of this forum.

Personnaly I started with EasyPCB, I think I have posted at least one of the sensor I did on the EasyPCB thread, door sensor powered by CR2032. With right part of PCB cut (becoming a 3.x*5cm PCB) it fits easily in a box smaller than yours. EasyPCB is great for starting as it has many options and all pins available, easy for ordering thanks to the DirtyPCB direct link. You can make a few sensors with it to get used and after that order other PCBs for smaller/more advanced sensors.
jModule is compact but I find it unconvenient to solder and use (with mix of pins from pro mini on top and jmodule on bottom), with too few pins broken out and it seems the creator of the board is not coming on the forum anymore. Very different from EasyPCB where you have active support from board creator and lot of examples and troubleshooting from newbies that will help you make a lot of progress on MySensors. At least it did for me ;)

[martim]

Hi @Nca78,

Thank you for your clear explanation. I will order some boards of Easy PCB and I hope your boards will arrive soon and then I will order those as well. This sound very nice.

[gohan]

@Nca78
How long is battery life of that door sensor on CR2032? Do you mind sharing the code of how you managed to get so low power requirements?

[Nca78]

@gohan I think I shared before in the EasyPCB thread, but I'll share the script again here tomorrow if you want, I'm not on my computer now.
The idea is to use a reed switch that is both normally opened and normally closed, connected to GND and pins 2&3 to have interrupts in the 2 states.
I set high with pullups the pin that is not connected to GND, so most of the time consumption is below 2uA. As soon as the CPU wakes up I set pin to low so it's connected only a few ms.

Battery life unknown but over 6months now and just started to eat the bulk of the capacity below 2.9V so I expect it to last over 2 years.

[gohan]

If you have a link to where you posted the code is just fine. Btw, would your sensor work with a lithium battery? I think a motion sensor would be more energy consuming than a reed switch

[Nca78]

@gohan yes in that case you would short Vcc and RAW using the jumper (or ignore that part and connect your battery to Vcc and GND directly), then put the XC6206 regulator for the radio so it would get 3.3V.
I'm thinking about making a sensor board for motion sensor + light sensor, powered by CR123, it would give long enough battery life even with the cheap 1$ sensors. CR123 is better than AA/AAA as it has most of it's capacity over 2.6/2.7V which is the limit for SR501 without voltage regulator.
But the CR123 are pretty expensive so not sure it's worth it.

My script for reed switch is here :
https://forum.mysensors.org/topic/2740/easy-newbie-pcb-for-mysensors/156

[gohan]

Normal cr123 can be found in boxes and you can pay it a little over 1$ each, but rechargeable ones are indeed more expensive and with much less capacity. I was also thinking about using 18650 batteries that would give peace of mind about battery life.

[Nca78]

Except for PIR because the very low power ones are not readily available, you will have no "peace of mind about battery life" using 18650. They are self discharging and they need a voltage regulator so for most of the "sensor" uses they will have lower battery life than CR2032 if your node is carefully assembled and programmed.

I'm interested in a link to purchase the cheap CR123 as those I found on Aliexpress are either expensive (>5$/unit) or have prohibitive shipping costs (>30$ and even sometimes ... >1000$ :) )

[gohan]

@Nca78

My colleague bought a box of 18 cr123a on Amazon branded keenstone for 26€