Design of omnidirectional three-dimensional capacitive sensor
Time:2023-03-19
Views:1138
Through analyzing and researching the problems encountered in students‘ electronic training courses, I invented an omnidirectional three-dimensional capacitive sensor, which solves the problem that traditional sensors can only sense in a single direction, and achieves the purpose of an omnidirectional three-dimensional sensor.
1、 Identify issues
When conducting practical training on the assembly and debugging of touch switches in the electronics class, when connecting the touch panel to the shell of a desktop computer, replacing the light bulb with an alarm, and converting it into a desktop computer burglar alarm. However, the alarm kept ringing when a person did not touch the casing of a desktop computer. Why is this happening? I suspect that the computer is grounded. I placed the computer on the counter and unplugged the power cord, but the alarm still kept ringing.
2、 Analyze the problem
Attaching a touchpad to the casing of a desktop computer simply makes the touchpad larger. Why can‘t the touchpad be enlarged? First of all, let‘s touch the antenna of FM radio. We found that the sound of FM radio with a lot of noise has become clear. The reason why FM radio becomes clear is that the distributed capacitance of the human body makes the signal at the receiving end of the FM radio antenna stronger, making the sound of FM radio clearer.
In the same way, when the touch panel becomes larger, its distributed capacitance becomes larger, and the signal becomes stronger. The base voltage of the transistor connected to the touch panel also becomes larger, causing the transistor to be in a saturated conduction state, causing the unidirectional thyristor to be in the ON state. At this time, the alarm is powered on and operates, emitting an alarm sound. Since it is a capacitor, where is its other pole? The other pole is the ground. During FM radio signal transmission, the transmitting antenna acts as an inductor, and the sky and ground are the two poles of capacitance, forming an LC oscillation circuit. The signal propagates between heaven and earth.
3、 Problem solving
Can we invent an omnidirectional three-dimensional capacitive sensor with reference to this principle and circuit? Should the electroscope come into contact with high voltage electricity during high voltage testing? The answer is: No.
At this point, I understand that as long as the touch panel is adjusted to the appropriate size, when the human body approaches a certain distance, the base voltage of the transistor connected to the touch panel is large enough to make the transistor in a saturated conduction state, and the unidirectional thyristor is turned on, the circuit or device controlled by the thyristor will work. At this time, we can use it to control circuits or devices such as sounds, alarms, and lights.
4、 Working principle
Using the LC principle, the wire connecting the base electrode of the triode to the thermos bottle is equivalent to the inductance L. The thermos bottle and the ground are the two electrodes of the capacitance C. The person is equivalent to the medium in the capacitance. When approaching the thermos bottle shell, the medium in the capacitance increases. The capacity of the capacitance C increases, and the inductance L sensing signal increases. When increasing to a certain amount, the base voltage of the triode connected to the touch panel is large enough to make the triode in a saturated conduction state, When the unidirectional thyristor is turned on, the circuit or equipment controlled by the thyristor will work. At this time, we can use it to control circuits or equipment such as sounds, alarms, lights, etc.
5、 Summary
This design solves the problem that traditional sensors can only sense in a single direction, achieving the purpose of omnidirectional stereo sensing. Through consulting relevant literature, no one else has conducted physical circuit research similar to the design in Figure 1. Figure 1 shows the physical circuit of this design.
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