On-off sensor circuit

This circuit can be set up in any computer you want to switch on/off by bringing your finger or any object close to the sensor.

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Data sheet

DesignSchema and circuit
ViewNo display
Supply voltage5 Volts

More info

The circuit is based on another one published in this website entitled "Proximity sensor power on for Pc" to be found among the circuits appropriated for the computer.

This on/off sensor is made up of two parts: the remote-control sensor (Circuit 1); the on/ off relay by impulse (Circuit 2).

Both circuits are linked up with two cables to 2-pin molex plugs.
The first circuit is made up of a remote-control based on the integrated infrared receiver IS471F.

The transmitter is an infrared LED that emits a modulated signal aimed at the 4-pin monitored by the IS471F. Being reflected in a nearby object, the signal is bounced off and captured by the IS471F internal demodulator.

The output originated in the 2-pin from the integrated circuit excites a relay for a time period that we can alter with the variable R6 resistor.

This relay output is connected to our second circuit (Circuit 2) through the connector marked ON.The running of this second circuit is based on the 4013 integrated circuit internally made up of two flip-flop.

Every time that our 4013 integrated receives an impulse through the 3-pin input, actually the "ON" connector (labeled CON1), we will give an impulse to the next flip-flop through the 11-pin.
Through this bistable oscillator each impulse at the input will be altered in the 13-pin output.

Having connected a transistor to the 13-pin output in order to set off a relay, this relay will be altered by each impulse and therefore will switch on/off whichever connected device. The circuit is 12 volts powered.

A small power supply with two outputs has been put in: a 12 volts that will feed the circuit 2 and another of 5 volts that will feed permanently the circuit 1.

The input ranges from 12 to 22 volts AC and we can get it directly from the power transformer of our system.

Connection between C1 and C2, as we have already said, is made possible through two 2-pin molex connectors, one for the 5 volts output and the other for the on/off impulse.

Be careful not to get it wrong when connecting them, even if when downloading the circuit board both are clearly singled out.

Circuit 1, distance sensor schema.

Esquema encendido apagado por sensor placa 1

Circuit 2, on/off switch schema.

Esquema encendido apagado por sensor placa 2

Circuit 1, sensor board circuit

Circuito encendido y apagado por sensor

Circuit 2, on/off switch system.

Circuito 2 del encendido apagado por sensor

The on-off circuit set up in one of our systems.

El circuito encendido apagado por sensor en un equipo

We fit the infrared led diode with a "hood" device to avoid the integrated receiver IS471F picking up the infrared emission which comes laterally from the diode.

The scheme and the circuit board should be in the same folder and they should have the same name, you should only change the extension to .sch for the scheme and to .brd for the circuit board, this way both of them will be recognized and associated by Eagle.

The file to download is compressed, to extract it, you should enter a password: www.kemisa.es

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