When using ‘smart’ power banks to supply electronics with low current requirements, they may decide that the current is so low, that it’s not actually supplying anything. While this might be good when things are actually disconnected or turned off, it causes a few issues when you need to sip small amounts of power for an extended amount of time.
To boost the device’s power demands up to a level that the power bank recognizes as on, Colin Hickey designed the Power Bank Keep-Alive based on 555 Timer (SMD). Extra power is drawn via an astable timing circuit, with resistors and capacitors configured to give it a 50% duty cycle, and the pulses drawing roughly 130mA. This pattern can be configured as needed using values produced from this timer calculator, but if you’re going to change circuitry around, it would be better to use his through-hole components kit. The kit is somewhat larger than the SMD version shown, but would make modding easier.
If you’d like a board specifically for exploring the 555 IC integral to this design, you might check out the through-hole/screw terminal kit featured here. Once you’ve got a handle on using the 555, you could then let the world know with the (should have worn a) 555 timer T-shirt!