There are so many products on Tindie that are stunningly cool, some showing incredibly impressive technical feats. Every now and again, however, a product jumps out at us because it solves a problem we have had recently! This Power Bank Keep Alive solves a particular problem where a load connected to a USB power supply draws so little current that the USB power bank switches off constantly.
I first faced this problem many years ago with the very cheap, but surprisingly useful in a pinch, early USB soldering irons. These irons had a crude motion detection which was a tiny soft spring inside a small metal tube. If the iron was moved the spring would touch the tube and the iron would remain in the heating state, however, if the iron was still for a while it would go into a power-saving mode with the heater off. If you were using this iron with a power bank the non-heating state wouldn’t draw enough power and the USB power bank would turn off. It’s incredibly annoying to then have to put everything down, pick up the power bank and press the switch. Just this week I’ve also had the problem of some small USB LED panels I use for photography doing the same thing, when the light is on it is fine but if I use the remote to turn the lights to standby mode, the device doesn’t draw enough current to keep the power bank alive.
Right, now I have vented my issues, enter the solution! The Power Bank Keep Alive is a simple board with USB-C connectors. Connect one end to your power bank and the other to your load and then the Keep Alive board regularly pulses the power line using a 555 timer in an astable circuit. It draws a constant 10mA and pulses regularly to 130mA, this is not enough to create a noticeable drain on your power bank but enough to keep the power bank online and running!
Supplied fully assembled the project author notes that this version is only suitable for 5V USB-C operation and won’t work well with USB-C PD systems. However, it’s worth checking out the Colin Hickey store as there are numerous versions of this product suitable for different USB setups.