Motion Sensor using the NE555

Entry to the 555 contest   German
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This simple motion sensor responds to changes in electric fields. Any person produces some electric charge when moving on isolating grounds. As soon as someone approaches the sensor, the LED lights for about 10 seconds. You can use it to secure your precious paintings in your private museum. To get this 555 cirquit working use a multimeter or an oscilloscope.

You can also use this circuit as an automatic torch. It lights up when you touch it. If you can´t find it in the dark just move your shoes a bit on the carpet and such gain some electric charge. This will trigger the light.

The circuit diagram shows a monostable using the NE555. 1 MOhm and 10 Microfarad come to a time constant of 10 seconds. The trigger input is connected to a Darlington made up by two BC547C. They give enough amplification to sense smallest currents caused by changes in the electric field.

Sensitivity mainly depends on the size of the sensor wire. In this case a small wire loop is connected to the Darlington base. But you can also use a longer wire up to 0.5 meters or any isolated metal plate.

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