How dangorus is an electric field motion sensor?

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hayaalsh

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Hi
In this year we had to make a device that include a circuit. My device is an electric field motion sensor.
The device and circuit are shown in the link: https://www.elektronik-labor.de/Notizen/555LEDeng.html

As a part of the project, we have to ask engineers about their opinion about the device. Please help me by answering these questions:

  1. As an engineer, what do you think about the device?
  2. This motion sensor that depends on electric field is cheeper than other motion sensor that depends on heat, however, it might be more dangerous. What is your opinion? And what would you suggest to over come this problem?
  3. Would you suggest some other application to the circuit?
  4. What is your full name and degree?

Thank you :smile:
 

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That appears to be an incomplete circuit-you've got a darlington pair configured to trigger the input to a monostable. The base of the darlington is connected to a square, which doesn't look dangerous at all. Pentagons and triangles, on the other hand, are known attack without provocation.

Kidding aside, what is that square supposed to be? An antenna? I don't really see anything 'dangerous' about that circuit.
 

This electric field sensor is but not very well defined to receive any particular fields whether DC or AC or RF, so it is not very precise.

YOu might use this to detect stray 60 Hz hum or strong 1MHz AM radios and people as conduits at short range.

PIR sensors are most reliable and cheap for motion sensing. but old motion sensing lights used pulsed IR which is detected continuously and detected by the change in ambient detected level and is very sensitive due to averaging out noise and very sensitive changes in average.

This circuit is not very sensitive for distance, but amusing at short distances.
 

Assuming that the circuit works for your application.
It is not dangerous because it does not radiate and if the power supply or the loop are correctly insulated there is no chance of an electric shock. Specially if battery operated, as shown.
 

the square represent an electric field.. If i move my finger inside that square, I trigger the circuit to enter the unstable state and the LED will light for about 10 seconds.
What i am afraid of is the electric field. Would it be dangerous if i enlarged the circuit and used higher voltage? I read that electic fields could cause heart attaks!
 

VERY high voltage fields can cause medical problems but for 6V to have any effect would probably take several years of continuous proximity of less than 1mm so I wouldn't worry about it. If anything is going to go wrong it will be the electic field discharging FROM the body into the transistor causing damage to it.

Brian.
 

You've lost me. The square is an electric field? How is it generated? How is your 'electric field' connected to the transistor?
 

the square is just a pc. of wire in a loop.

It acts as a capacitor and weak loop antenna. It can be triggered by proximity effects of e-field from 50/60Hz or possibly a strong 1MHz AM radio signal may affect it. Unlikely 1GHz cell phone will pass thru trigger amp.
 

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