This document goes deep into technical details and explains the HARDWARIO TOWER - Industrial IoT Kit power management on the hardware level.
The HARDWARIO TOWER - Industrial IoT Kit has been designed the way to allow the connection of multiple power sources.
For example, this allows the Core Module to be powered from a USB cable and also have batteries inserted in the Battery Module at the same time. HARDWARIO TOWER automatically solves the problem by selecting the appropriate power sources.
What does it mean?
For example, when an external power supply (adapter or USB) is connected, the battery is disconnected. It is also possible to have multiple external sources connected at the same time - for example, the adapter plugged into the Power Module and the USB cable in the Core Module.
In this case, the module that is located in the physically lower layer will take priority and will be the one that will deliver power to the system.
Power Management Explanation
The TOWER header has two signals for system power distribution:
- VDD - Positive supply rail
- 3.1 V when powering from batteries
- 3.3 V from the external power supply
- GND - Ground (negative rail)
The module that can deliver power in the system is called the energizer. The energy is supplied either using an external power supply, or batteries.
In both cases, an energizer contains the electronic circuit for intelligent power management.
This additional electronics circuit controls (or is controlled by) two auxiliary signals on the TOWER header:
This signal disconnects the batteries and prevents their discharging when another power source is available and the batteries are not needed.
This signal is physically split into two parts:
- This signal is on the bottom side of the module (the side with the pins) and it disconnects the power supply output of the given module.
- Each power source module (except the battery) uses VDD_OFF_IN from the bottom side, telling it to disconnect power as there is another active power source (logic 1 = disconnect power),
- This signal is on the top side of the module (the side with the sockets) and it is chained to the VDD_OFF_IN signal of the module above the given one.
- Each power source module (except the battery) provides a VDD_OFF_OUT signal on the top side of the module, indicating to other modules it does provide power.
Possible power source modules at this moment are Power Module and Core Module (when connected to USB). If stacked, the lowest one takes priority and by this logic, there are two possibilities:
- Core Module on top of Power Module, TOWER is powered from Power Module
- Core Module below Power Module, TOWER is powered from USB (speaking about 3.3V VDD)
You should be wary of this, in case you are trying to build a device that includes for example the Smart LED Strip. The device will not work as expected if you put Core Module below the Power Module.
This is an example of the electronic circuit of the battery energizer.
This is an example of the electronics circuit of the energizer powered by an external power supply.