I have successfully built an RFID reader/logger, and have it working as I want. Now that it must work for a living in a wildlife research application, it will have to sit out in the field for weeks awaiting a (rare) event before attempting to read an RFID tag in a fairly leisurely time-frame (several minutes if necessary). The device will then sit (preferably) unpowered until re-set by the operator (me). I have read a good deal about Arduino sleep modes, but it seems to me that simply switching the power off until the event happens would save a lot more power. For instance, I could use a NO reed switch to control a relay and power-up the Arduino. However, as an electronics noobie I have no idea how the voltage spikes and switch-bouncing at startup will affect (a) the Arduino, or (b) the way my code works.
As it happens, the power socket on my Uno makes a dicky contact, which I guess simulates what might happen. I have found that my code sometimes creates a number of empty files on the SD card, whereas it should create only one (at the start) which is finally closed off when the reader is presented with a master tag. It does writes data correctly to the last file created. I guess the mad file-creating behaviour may be caused by intermittent power supply as I connect the battery, in which case I can maybe correct it by building in a software delay at start-up - but is there any other software pitfall I should be on guard about?
And what about effects on the hardware? Since this device is for standalone use, I am contemplating building more units based on a minimal 'Arduino' (almost just the Atmega chip). Is there any extra component I really should include to avoid the possibility of damage at power-up and power-down?
Apologies if this scenario has already been discussed elsewhere on this forum - I don't know the lingo well enough to know what to search for!