Choosing low power microcontrollers to run with a solar panel

Question

I am starting a project which will control a small motor, some LEDs for illumination and read some analog sensors and I need to power it via a solar panel. I am looking for the best option on microcontroller to use but I don't know much about the topic. I need that such microcontroller have 2 analog inputs, 8 digital I/O, at least one interrupt pin, a 16 bit timer would help but an 8 bit also would do the job. The speed is not really an issue here but the power consumption is the thing that concerns me the most.

I was watching son ESP32 and I like the fact that they have dual core and are low consumption but I won't use the WiFi module and I just feel that it would be a waste.

Answer 1

To be honest if you are planning to run a motor, that is likely to be the biggest factor when it comes to power draw.

You are going to need a battery/super capacitor to buffer the solar output for the motor and that's before we even start thinking about what happens when it's dark.

Once you've sized the solar panel and the storage to cover the motor usage, then you will probably find you have enough spare to run the micro controller and sensors.

Answer 2

There are experimental MCUs designed for energy harvesting applications. These operate at extremely low supply voltages (~0.5 V if I remember right), and can potentially be run directly off a 1 or 2 cell PV array (removing the energy cost of a regulator). I'm not sure if these have reached general production yet.

For the design you are proposing, some sort of split rail design seems necessary. One 'always on' very low power side, and one high current side (probably a rechargeable cell which is charged during daytime). You need to carefully calculate if the total of 24/7 standby plus all of the active cycles still allow you to operate with energy to spare from the panel.

Under ultra-low power MCUs, you should be able to find 200-300nA standby states - but the sensors and any power regulation will easily significantly increase this. For some of these, you should be able to find some eval boards targeting IoT applications. Don't forget that if these have a USB debug interface, you will want to disable that interface for best power performance.

Answer 3

A PIC microcontroller can be run at fairly low power. Further, it can be put into "sleep" mode when you don't need it to be active. You can reduce power consumption to nearly nothing (relative to your battery capacity). You can set it to wake with an interrupt based on a pre-set time or an external trigger (signal on a specific pin changing from low to high, for example). Getting a PIC at the component-level and programming requires more experience and learning curve than, say, an Arduino.

There is an ability to put an Arduino microcontroller to sleep (I found this, for example: link). You would need to research or measure for yourself to know how much power is actually reduced. I imagine it's more power-hungry than a PIC in sleep, but may still be good enough for your needs.

Lastly, you may look at Particle microcontrollers, if you end up wanting wifi or cellular connection built in. They are probably not the lowest power consumption, but are great for ease of use. They do have some sleep mode functions that you could explore (you may start here: link

Happy coding!