The circuit’s built-in power supply has been kept very simple. The single-cell Li-ion battery (BAT) provides a nominal voltage on 3.7 V. The power supply also drives a “luxury” white LED light source ...

The hack to keep a color-changing LED’s cycle going is to add a capacitor to retain some charge between pulses, and a diode to prevent that charge from draining back into the rest of the circuit ...

When there is any break in the connecting cables or any loose contacts in the terminals, no more current passes and D2 and D3 reverse biases. This turns off T2 and T1 conducts .LED lights indicating ...