The circuit’s pretty simple, basicly it’s just a voltage regulator. Both the LM317 and the REG1117A (LDO) fit the PCB, maybe there are even more types that I’m aware of that can be used on it. I did add one extra thing: a LED that shows if the connected device is consuming power. To do this I used a shunt resistor and a current converter. I choose 0.2 ohm for the shunt, since it’s not hard to come by and should only drop 0.1V @ 500mA. Either an INA168 (current output) or an INA193-198 (INA194 is best in this case) (voltage output) will fit as current converter. The trip point at which the LED should start to burn can easily be adjusted by one resistor (in case of the INA168) or by two (in case of the INA193-198). In the schematic it is set at 100mA using an INA168 using a 950k resistor. The Schmit buffer is a Texas Instruments Little Logic chip (1G17).
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