Hi Stan,
Schematics of battery pack:
https://download.mikroe.com/documents/specials/hexiwear/hexiwear-battery-pack-schematic-v102.pdf
If I get it well, you want Rapid IoT to power the whole hexiwear battery pack (and more specifically the click board). The HW as is does not allow for it
If you look at the battery pack schematic carefully and in association with Rapid Iot schematic you will note:
- Only 5V is distributed via the connector between kit and battery pack
- 5V on this connector is 'an input' to RApid Iot:
So your smoke detector does neither receive 5V nor 3V when not battery is enabled in the battery pack.
I took a look at how you could hack the HW to enable your use case but not sure whether you want to do that. You must be very carefull and make sound decisions but I came up with 2 options:
OPTION1:
On Rapid Iot:
1. Isolate VCC_5VEXT on the kit by removing D3 & R16 - this means you will no longer charge your kit when put on a battery pack or a docking station. You will still be able to charge it via USB (and power later on your battery pack via USB)
2. Connect TP5 to TP1 (This will connect Rapid IoT Battery output to the connector going out of RapidIot
On the battery pack:
It is more complicated as you have to rework he 5V line coming out of the Rapid IoT connector to feed the VCC BAT line on the hexiwear battery back (cut some lines, soldering...). You would need access to the board layout
OPTION2:
A very quick &dirty alternative would be the following:
- Open Rapid Iot kit, locate a place where you can solder a wire to catch VBAT (TP5, TP32, J11) and get this wire out feeding VCC BAT on the hexiwear battery pack. This will be simpler but you will have a wire coming out of the kit hanging around and your battery pack and this kit will be tied together forever :smileywink:
- Be EXTREMELY carefull though :smileyshocked:, not to connect a battery to Rapid IoT battery directly... you would create damage and start fire. Better protect each battery line with a resistor / diode so if you forget your mods in the future, you will not manage associated risk.
We took measures on the kit to manage those potential conflicts as per example below:
