Test equipment cable monitor LiIon
Using the "High Side DC Current Sensor Breakout" Adafruit/904 or Adafruit/2650. This is based on INA219 using a shunt R of 0.1ohms that can measure to 0.1mA - sufficient resolution for the measuring the Mayfly's expected sleep current of ~0.35mA.
Build: For the cable, the LiIon battery side is the female socket, screw the red wire into -Ve. The Mayfly side is the male header, screw that red wire into the +Ve socket.
Connect the blacks wires together - optionally add the capacitor. The black wires can be soldered or crimped, and should be protected with an insulation eg electrician's tape.
CapacitorNotes: I like the capacitor as I had some some problems with Mayfly reseting with meters in the cable. Also the Adafruit driver code for the INA219 references the device can be reset with current surges. I see a hardware capacitor solution to a potential current surge, rather that the software solution they use. To add the capacitor, note the +ve and -ve sides. Add the "+" leg to the redwire going to the Mayfly and "-" leg to black wire.
The battery cable is two parts
- Digikey/1528-1126-ND Adafruit/261 CABLE ASSY JST PH 2PIN 4"
- Dk/1528-2617-ND Adafruit/3814 JST PH 2 PIN CABLE MALE HEADER
or a single battery extension cable, Adafruit/1131, that is cut in two and trimmed.
Optional capacitor, low ESR and this is one I used on another project
- Dk/732-9079-1-ND CAP ALUM 680UF 20% 10V THRU HOLE LOW ESR
For the Adafruit/904 also need a Grove cable. Cut in two and strip ends and solder in the Adafruit/904
- Dk/1597-1083-ND 110990037 GROVE 2MM 4PIN R/A CONN 10PACK
In the picture the LiIon +ve is connected to the INA219B, the Mayfly#1 with the USB cable polls the I2C and reports current.
The Mayfly#2 (with screwdriver & Xbee) has its power solely provided by the LiIon.
The J2/FTDI monitoring cable has its power and DTR pins clipped so its only monitoring, and not providing power or causing a tty reset.
(code https://github.com/neilh10/ModularSnsrsNh/tree/test_nh1/sensor_tests or https://github.com/neilh10/ModularSnsrsNh#c85f34f85ccf2952305e166c54172e0af9bb2a76 )
Discussion at https://github.com/EnviroDIY/EnviroDIY_Mayfly_Logger/issues/21
For the Adafruit/2650 the parts need to be assembled (tbd)