“It’s very simple circuit for showing operational status of raspberry pi (Hereinafter as RPI).
Maybe it’s useful when you running RPI as headless (without monitor).
Sometimes I’m concerned when is right time for completely power-off after shutdown RPI.
Therefore, this circuit is made to notify the right time for power-off.
Also it can show you the headless running RPI doing something.. at least make bi-color LED blinking.
This circuit is made base on very common LED multi-vibrator so called as LED blinker.
Based on the LED blinker I’m adding the following feature to make RPI shutdown indicator (Hereinafter as INDICATOR).
- Using opto-coupler to interface with RPI (Because I want to isolate this circuit completely with RPI in term of power supply. Actually I have bad experience burning RPI with hardwiring)
- USB Type-B power adaptor is used for this circuit is connecting with common hand-phone charger which is highly available and supply 5V exactly
I’m supposing external power source usage can minimize problems (e.g. grounding with RPI, mistakenly connecting high voltage to GPIO) and less burdening RPI.
Although this circuit is quite simple, I’m planning to develop more complex ones later which are drawing quite significant current from GPIO.”