I got to the house ready to get to work - my NUC with all the bluetooth doohickey configured, a simple shell script to pipe the serial output to a rotated text file while I figure out how to store the data for the long term, the HC-06 serial bluetooth dongle, and the electronics project box that contains all the little miscellaneous wires and parts.
Getting the NUC up and running was the easy part, luring me into a false sense of achievement even though there's nothing special about it.
|Wee! Computer is up and running|
Second possible issue was the power consumption of the HC-06 bluetooth module. The datasheet shows average pairing current of about 25mA, with spikes up to 40mA. However, once paired, the current consumption should stay at around 8mA. The Trimetric 2025 down-converts the 48V available at the battery down to 5V using linear regulators, so the current available at the 5V rail is fairly limited. Bogart engineering folks said there should be at least 5mA available at the 5V rail, and that the display uses another 15~20mA or so. I was hoping that by turning the display off and by putting a little capacitor to take the load, I'd be able to get the HC-06 module to at least pair after which I'd be able to turn the display back on and use the Battery Monitor while recording the data.
For both the issues, unfortunately, I was proven overly optimistic.
|Range testing the Bluetooth Module|
The wall where the battery monitor is mounted is behind the counters, and there's a heavy one-piece granite countertop making it very difficult to access the area. There's no other connection in the box other than the wires coming from the battery box, no easy way to get the data out or power in. And I really didn't want to look for yet another 48V to 5V converter which may also skew the voltage readings in the battery monitor.
I went down to the subfloor to see if there was any hope from underneath.
|I see the light!|
This means that I probably need to go back to ESP8266 for sending the data back to the computer. Wifi should have more than enough range to, and now that power's no concern, Wifi's back on the table! I'm leaning towards having the ESP8266 simply sending out UDP packets with the serial data to a hardcoded address, but we'll see what's easiest to implement. Hmm, I wonder if there's enough memory to fit a Lua VM in the ESP8266!