Patent ID: 9569949
Date: 2017-02-14
CPC Classifications: G08B,H02J,H04M

Claim:
1. An electronic circuit for indicating when a smart phone is charged, the electronic circuit comprising: an operational amplifier circuit for sensing current draw of the smart phone; an first comparator circuit for detecting a smart phone and a smart phone charger are connected to the electronic circuit; a second comparator circuit for monitoring a smart phone charge status; a buzzer pulse generator circuit for driving a piezo buzzer and a light emitting diode; a relay circuit for disabling the buzzer pulse generator circuit; an audible piezo buzzer circuit for an audible alarm when the smart phone is charged; a first light emitting diode circuit to provide a visual alarm when the smart phone is charged; a second light emitting diode circuit for indicating when the electronic circuit is connected to a power supply; a first connector for enabling connection to the smart phone; a second connector for enabling connection to the smart phone charger; wherein the buzzer pulse generator further comprises: a LM555 timer integrated circuit (IC) wherein a Reset and a positive voltage (V+) pins are connected to a common contact of the relay circuit, an output pin configured with a first and second resistor of the buzzer pulse generator circuit to provide a reference voltage capable of driving a base connection of a transistor in the audible buzzer circuit, a Discharge pin configured with a third and fourth resistor of the buzzer pulse generator circuit in series with a first capacitor of the buzzer pulse generator circuit to set a rate of the LM555 output discharge voltage, a trigger pin (TRIG) and a threshold pin (THR) connected between the fourth resistor of the buzzer pulse generator circuit and the first capacitor of the buzzer pulse generator circuit to enable/disable the LM555 IC when power is applied/disconnected, a control pin (CV) connected to a ground node through a second capacitor of the buzzer pulse generator circuit to filter a supply voltage and a ground pin (GND) is connected to the ground node.