Every scrap of power is precious when it comes to power harvesting, and working with such designs usually means getting cozy with a microcontroller’s low-power tricks and sleep modes. But in the case of the Ultra Low Power Energy Harvester design by [bobricius], the attached microcontroller doesn’t need to worry about managing power at all — as long as it can finish its job fast enough.

The idea is to use solar energy to fill a capacitor, then turn on the microcontroller and let it run normally until the power runs out. As a result, a microcontroller may only have a runtime in the range of dozens of microseconds, but that’s just fine if it’s enough time to, for example, read a sensor and transmit a packet. In early tests, [bobricius] was able to reliably transmit a 16-bit value wirelessly every 30 minutes using a small array of photodiodes as the power supply. That’s the other interesting thing; [bobricius] uses an array of BPW34 photodiodes to gather solar power. The datasheet describes them as silicon photodiodes, but they can be effectively used as tiny plastic-enclosed solar cells. They are readily available and can be arranged in a variety of configurations, while also being fairly durable.

Charging a capacitor then running a load for a short amount of time is one of the simplest ways to manage solar energy, and it requires no unusual components or fancy charge controllers. As long as the load doesn’t mind a short runtime, it can be an effective way to turn even indoor light into a figuratively free power source.

The SPINES (Self-Powered IoT Node for Environmental Sensing) Mote is a wireless IoT environmental sensor, but don’t let the neatly packed single PCB fool you into thinking it’s not hackable. [Macro Yau] specifically designed SPINES to be highly modular in order to make designing an energy harvesting sensor node an easier task. The way [Macro] sees it, there are two big hurdles to development: one is the energy harvesting itself, and the other is the software required to manage the use of every precious joule of that harvested energy.

[Macro] designed the single board SPINES Mote in a way that the energy harvesting portion can be used independently, and easily integrated into other designs. In addition, an Arduino library is being developed to make it easy for the power management to be done behind the scenes, allowing a developer to concentrate on the application itself. A solar-powered wireless sensor node is one thing, but helping people get their ideas up and running faster in the process is wonderful to see.

Javier Betancor is developing a system which collects power as you ride a bike, with the goal of powering data collection and lighting. “imPulse” uses a stepper motor for power generation, along with a geared hub to make the motor spin at multiples of the wheel speed.

While the project is still a prototype, the headlights and rear lighting assemblies already look very good, and CAD files as well as Arduino code are available here.

The aim of this project is to provide a cost-effective alternative to power generation on bikes using conventional stepper motors while adding other capabilities, such as: 

– An integrated data logging system to monitor power generated on each trip.

– A smart lighting system with addressable LEDs, working as indicators, braking lights and headlights, incorporating Light Dependant Resistors (LDRs) to sense the environment and to reduce the risk of glare.

– Power Distribution Board (PDB) to charge two different/generic powerbanks. While one powerbank is charged, the other one is used to supply energy to the system.

You can see a prototype of the lighting system in the video below, using an Arduino Uno for control as a turn signal and brake light, as well as a constant beam for visibility. Find additional information and follow along with Betancor’s progress in his Hackaday log.