Am Wed, 26 Feb 2014 17:53:24 +0100 hat "Dr. H. Nikolaus Schaller" hns@goldelico.com geschrieben:
- UMTS module activity sensor
Some people would like to reliably disenable the UMTS module because they don't trust the power-off command or the power indicator LED provided by the module. So they want some external mechanical switch
- or alternatively an activity indicator LED that uses external
hardware to monitor the module's power drain. This can quite easily be done (there are current sensor chips with a threshold that can make an LED illuminate as soon as the module draws more than let's say 5 or 50mA). One minor problem is that such a circuit adds a voltage drop which must be kept very small since the module may draw 2-3 Amperes from the battery during transmission peaks. A mechanical switch must also have a very low resistance and should be very reliable.
Be careful about a switch! We do NOT want to add a physical switch somewhere at the case! Not all units will have UMTS, and a switch adds costs (more complicated case mold, needs to manually be assembled, etc.)
So in case an LED does not work, we will not include anything else - I still think the chance of the module being compromised is very very slim.