I am working on a project and the Wroom32D was an ideal fit for the use case I am attempting to provide a solution to.
Trying to implement a mesh network which will usually be situated in a remote location, where little to no human interaction with the device occurs. As such, a core requirement for the device is sustainable power supply without the need to consistently change the batteries.
Short of hooking individual relay and friend nodes with a bigger battery (which will not work for this particular use case) or using solar (customers will not pay for solar for each node), I decided to have separate power domains for the ESP32 and the sensors
The ESP32 is a relatively power hungry RF-MCU and as such I decided by factory default to power the system (MCU + Sensors) using Alkaline cells in series (2 of them). I will be boosting the voltage obviously to 3.3v ( I am still very unsure of this qw there seems to be a warning label with SMPSs regarding RF circuits). This will not lock customers to always purchasing an extra battery for the sensors. Customers that do not want to extend power capacity of the device can still power the system and will depend on the power management scheme adopted.
I have attached 4 schematic designs.
- Design 1 (Design_ask.png) - I am using the Power good signal of a DC boost converter to alert the MCU to switch off the Mosfet that directs power to the sensors from the ALkaline cells. My concern here is this will not happen before the sensor power domain sees the voltage at the Vout pin of the boost converter.
- Design 2 (Design_ask_update.png) - Changed to a simple boost converter with an enable input. This will be activated (but delayed with the capacitor present ) while the same voltage shuts off the mosfet. I wasnt sure if the delay assumption was accurate. I am not even sure if the design is correct.
- Design 3 (Design_ask_update2.png) - ALtered the design a bit to place the switching task on the ESP32. With this setup, the voltage at the coin cell line is measured by the ADC in esp32 and the appropriate pin in toggled (or not) depending on the voltage level measured. The enable input of the converter is still controlled by the MCU. My main cause for concern is the power consumption in operating the mosfet as well as keeping the enable on.
- Design 4(Design_ask_update3.png) - Did some extra research and found a concept called ganging which includes chaining GPIO pins together by shorting them. This is done to apparently increase the total drive strength of the MCU when it sources/sinks. I decided to replace the transistor from the previous design with a ganged set of GPIOs. I have read from several sources that as you increase the number of GPIO pin drivers, power dissipation by the device starts increasing. I would like to confirm if it is possible to do this with the ESP32 gpio pins.
Please be aware that the sensors will be carefully chosen which are relatively low power ranging from 100s of microamps to a few milliamps (some might reach 10s of milliamps). But as I would like to design for extensibility, I have to make enough headroom for potential extension to the system.
I would like to know if the final design is feasible with the esp32. If not, what about the other designs? Any modifications to make them more efficient?
Thanks a lot in anticipation.