This Window Open Sensor (WOS) has a great WAF because it makes use of a nice case, harvested from a very cheap window alarm. This alarm module holds two AAA batteries and has a switch, a buzzer, a magnet and a reed contact.
We remove the electronics, the buzzer and the switch. Then we replace the electronics with a Sensebender with NRF24L01+ module, which just fits inside.
You can use the delivered magnet, but the one in the BOM is much smaller. So I glue that on the window instead. The module can be fixed on the window with two of the loop/hook (velcro) pads listed in the BOM, which works far better that the self-adhesive tape that comes standard on the alarm module.
Prepare for fitting a SensebenderMicro and radio:
I always use rechargeable batteries. As a consequence, the batteries condition is always indicated as less than 50%.
Not all alarm modules are the same. The ones I had first, only barely fit a sensebender micro, the ones I ordered later, have a more shiny plastic, and fit a Arduino mini pro - something to try out later.
|Qty||Value||Device||Package||Parts||Description||MF||MPN||Aliexpress or Ebay link|
|2||AAA||battery (rechargeable Ni-MH works fine)|
|2||2cm diameter||Hook-Loop to attach (Velcro)||https://www.aliexpress.com/item//32680806552.html|