You don't need to prototype the 555 timer circuit featured on [Great Scott!]. There is a very similar product you can buy from Colin Hickey's store https://store.eplop.co.uk/product/smd-keepalive/
Power Bank Keep-Alive based on 555 Timer
When I tried Colin Hickey's 555 circuit I found the duty cycle to be suboptimal for most USB powerbanks. Mr Carlson's Lab had designed a similar 555 timer circuit with timings adjusted to shunt a 51ohm resistor across the USB power rails for 2.5 seconds and disconnect it for 25 seconds https://youtu.be/lOL3ic8msas
I tried modifying Colin Hickey's Power bank Keep-alive circuit to function more like Mr Carlson's Lab design. I got it to draw 110mA for 3 seconds and under 2mA for 23 seconds.
In spite of the additional through-hole components I was able to use the Eplop Electronics PCB unmodified and still fit everything inside the same 3D printed case that was sold as an option. I even added an indicator LED to see what state the 555 timer was in.
I did find one powerbank in my collection for which the 23 seconds was too long a wait for the next high current pulse. It switches off after 6 seconds
I would later add a fast mode dip switch to the circuit
[Adreas Spiess] does his own twist on the USB Powerbank keep-alive circuit -- using a modern version #ATTiny to first characterise the switch-off delay required https://youtu.be/SgV6_Y_sg4k
He also runs afoul of chip fakers on Aliexpress #microcontroller#electronics
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