Tom's Life Bits

MightyBoost is a 5V/1.5A boost/charger/backup PSU, meant for embedded systems running from a 5V input. It requires a LiPo battery that kicks in if external power is lost (2Ah+ recommended). Paired with Moteino it can accept a PowerButton for no-login shutdowns, much like ATXRaspi.

• 5A-1.5A boost supply
• LiPoly charger (default 200mA, 500mA via jumper, see explanation below)
• Provide power from input as long as it’s present and charge LiPoly
• Act as backup supply when power is cutoff and switches to LiPoly battery source
• Moteino controlled mode (default) where Moteino will provide the smart features of a shutdown button and signalling to your Pi, BBB, etc. Moteino also senses when power is switched to backup and can sense battery level and make decisions when to signal Pi to shutdown cleanly (ie immediately or when battery finally runs out, etc.). That means you can control it in any way you want based on a number of inputs and conditions. Sample code will follow the release.
• Standalone mode (via jumper) where it can be used as LiPoly to 5V boost supply. This allows you to power anything requiring 5V including for instance your internet modem or router or other things like that which you’d want to stay alive during an outage
• Provides a boost for your Android/iPhone/iPad when in need
• When coupled with Moteino, it could act as a compact smart backup PSU + Moteino gateway for your home automation, when a RFM69/RFM12B transceiver is added.
  

To change the charging current you need to cut the default jumper open and resolder the other jumper. Also to use MightyBoost in standalone mode, just solder the “5V* OUT ON” jumper to enable the “5V*” output to always be ON (ie power your internet modem).

Charging will be set around 200mA by default (and not 500mA) and that’s because your input power supply must be able to deliver whatever the load takes + the charging current, otherwise the charger will shutdown and not charge the LiPoly battery, so this will be a requirement. For instance if your Pi takes 500mA, then your supply will need to be 700mA at the very least, I would opt for a 1A to give a hefty margin if the Pi spikes for any reason. If you use the jumper to set charging at 500mA then you need at least a 1A supply, I would add 300mA more for that safe margin. If you power your BBB through MightyBoost you should probably look for a 2A supply.

To duplicate the features of ATXRaspi and monitor the battery level and make decisions, I published a sample sketch here. Use a simple Moteino (no transceiver needed) to control MightyBoost and emulate the behavior of ATXRaspi. If you want to get fancy and send control messages and get battery level over wireless you will need to add a transceiver to your Moteino.

** Note for when paired with Moteino: The BootOK signal coming from a RaspberryPi will be around 1.7V even after the Pi shuts off. It’s not entirely clear if this was always the case or it started happening with recent distributions of Rasbpian. This causes the BootOK signal to read as HIGH on the 3.3V running Moteino. This is not an issue on ATXRaspi since that board runs at 5V and 1.7V will read as LOW. To fix this issue, the BootOK signal in MightyBoost R2 has been moved to A0 (D14) and the sketch will read A0 (D14) for the BootOK signal. If you have a MightyBoost R1 please see the guide for differences.