The purpose of this demo is to test a electrical circuit protection system from a harful alternate voltage. The measurement was made from both phase and neutral wiring in a two-phase circuit, that means 110 volts under normal circumstances.

Items list:

• Arduino uno;
• ESP8266-01;
• ac voltage sensor;
• 5v relay module.

Basically the project relies on an Arduino board that connects to a cloud service called Thingspeak by HTTP data protocol. The transport happeans through an ESP8266-01 as it has wi-fi built-in and then can reach the Internet. The electronic circuitry is about an ac voltage sensor and a 5v relay module that do respectively voltage readings for phase-neutral and (dis)connecting the load from the electrical circuit.

There is a specific regulation related to the voltage range but I´ll just assume a voltage above/below 20% from its normal value would be harmful.

Because I didn´t have a signal generator to inject a sinusoidal wave with variable amplitude, I made an adaptation on an electronic circuit so I could emulate a casual harmful voltage about 80v that was providade to a load (bulb light). The voltage could then decrease after turning on a switch within the circuitry. Just after that, the system realizes the voltage would cause damage to the load and then sends a “LOW” instruction to the relay which disconnects the load from the power utility.
There´s also a push button on the prototype, that emulates when the voltage comes back to normal, but it was programmed to happen only if the push button is kept pressed for more than a second, then the system assumes it´s safe to connect the load to the power utility again and sends a “HIGH” instruction to the relay.

Both normal and harmful voltage readings were recorded in Thingspeak which also has an alert service that uses Twitter to send notification messages and can warn when the relay disconnects the load for protection.

PS. The voltage readings by the sensor differ a little bit from the multimeter measurements but such inaccuracy is just about 3% and is due to the fact that the multimeter has a more complex circuitry behind it in comparison to the sensor.

 

The sensor readings generated a graph at Thingspeak, available on the following link.

AC Voltage – ThingSpeak IoT

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