Welcome to EnviroDIY, a community for do-it-yourself environmental science and monitoring. EnviroDIY is part of WikiWatershed, a web toolkit designed to help citizens, conservation practitioners, municipal decision-makers, researchers, educators, and students advance knowledge and stewardship of fresh water. New to EnviroDIY? Start here

Reply To: Stability Testing ~ how to do it?

Home Forums Mayfly Data Logger Stability Testing ~ how to do it? Reply To: Stability Testing ~ how to do it?

#15011
neilh
Participant

I’ve received more “LTE Bee Adapter” cards, and looking to experiment using it to investigate why the  Xbee WiFi S6B is not reliably connecting to the local wifi network. https://github.com/neilh10/ModularSensors/issues/21

The LTE Bee Adapter card provides power directly from the LiIon battery, control of the Xbee reset, and potentially also an Xbee power OFF capability.

The WiFi S6B is specified for 3.14 to 3.46V so this isn’t a good long term solution. The LiIon Battery can be up to 4.2V.

Part of my tests are to let the LiIon battery discharge, as might be expected in the field with little sun, and then incrementally charge it back up, as solar is available, possibly over days. This is one of the most difficult parts of powering (and testing), slowly varying power availability.  This appears to be causing some unreliability,  and I haven’t yet been able to identify if it is something in my setup or something else.

Part of  LiIon battery discharge characteristic, is its voltage drops and internal impedance rises. The priority is to keep the Mayfly running, with good traceable wall time, taking sensor readings (with wall time)  and then transmit (when power available) to the internet. The rate of voltage drop, and impedance rise, is dependent on the capacity of the LiIon battery.  I’m standardizing on a 4AHR outdoor (-10C?) rated battery. LiIon impedance also rises as temperature drops. So there is a narrow window of when the battery, as measured by its voltage, can support the highest dynamic power demand – typically when using RF power.  For the real world, discharging a 4AHR battery can take a week, which is a good thing normally, but for testing I’m having to be creative.

So the first part of the test with WiFi S6B/LTE Bee Adapter was to see if it would get into the state of not connect to the WiFi network -~ and if did, would the RESET bring it out.  However in overnight/24hrs it has connected to the WiFi every time as expected. So that’s a good thing. (Though MMW POSTs gave my a “201” in 500mS about 1-in-5 times, with the more typical no response timeout being 3000mS)

So going to go to back to standard powering WiFi, but with logic sensors on the WiFi S6B, and also add 0.1uF ceramic decoupling capacitance directly to the WiFi module pins, which will allow me to monitor the Vcc as well as logic sensor.