Power banks are ubiquitous, and because they offer 5V with an easy to use USB port, they often find use in wireless projects. IoT projects in particular often take advantage of the high power density and small form factor. But most power banks have a feature to turn themselves off when the attached device (presumed to be a phone or other device that requires charging) reaches full charge. They do this by sensing the current draw, watching for it to fall below a certain threshold.
This can be a major issue for projects with a low, steady standby current, which also need bursts of high current when transmitting. This smart device helps keep your power bank from switching off when your device is not drawing much current — and it does it without drawing excessive power!
This design takes advantage of the fact that before shutting off due to low current draw, power banks have a delay of 5-10 seconds. By drawing very small pulses of current every few seconds, the circuitry is kept awake. The amount of energy actually used is completely configurable, depending on your individual power bank. You can have it draw up to 140mA for any length of time, at intervals which are also customizable. This allows it to be used with a wide variety of power banks.
Sure, some power banks don’t have this feature, or might have a cutoff which is below what your device draws. But finding the perfect power bank could be a costly and difficult endeavour, when you can just use whatever power bank is the most economical paired with this device!
The source code and design files are freely available for modification from GitHub. Happy hacking!