I am working on an Arduino project that should be sealed, with the possibility to switch off when the user wants. A solution I have seen on commercial products is the use of a Reed switch, normally closed. When there is no magnet, the board is powered on. When the user adds a magnet at a given location on the box containing the electronics, the board is powered off.
I have been looking for such components online, but I have a hard time finding tutorials / explanations for Reed switch n00bs like me. So what I need is some help understanding a datasheet / understanding if what I think about will work.
My speccing needed:
- range of operating temperatures: -40C to 30C (this is important, polar environment use! -60C would be even better, but that seems hard to find).
- switching on and off electronics working at 3.3V
- max power draw by the electronics: up to around 200mA
- way to close the reed switch: by using a small rare earth magnet (these are surprisingly strong, but I do not have a spec available), through a plastic wall of approximately 1.5mm thickness.
After searching online I am considering this switch: MDRR-DT Series https://www.littelfuse.com/products/magnetic-sensors-and-reed-switches/reed-switches/mdrr-dt.aspx .
I like it better formed (i.e. F version, less risk to have the 2 legs getting in contact). I am quite unsure about which sensitivity to use though. I want to be sure that it is not too sensitive and does not close unexpectedly, but I still want to be able to close with my quite powerful rare earth magnet. Should I go for something like 25-30AT then? That would be like this: https://no.mouser.com/ProductDetail/Littelfuse/MDRR-DT-25-30-F/?qs=nyo4TFax6New9CGWZwJeTA%3D%3D .
Anything I am not thinking about that is important when considering using Reed switches for such applications?
What I am confused about is in part why AT is given as a range. Does AT 15-25 well mean that the switching is happening somewhere between 15 and 25, or that at above 25 weird things happen?