With the rapid development of Internet of Things technology, the demand is becoming more and more extensive. In addition to the common communication switch methods, most of the related electrical appliances are also equipped with human body induction or touch switch methods. Recently, customers have demanded such a solution, requiring the minimum cost to achieve a sensing distance of 6-7cm. We chose the TC301D chip, which is powered by 3-5v DC. After a lot of tests, we found that the effect is good and the stability is high. Our testing process is given below for reference only by peers with such needs.

Compared with external infrared sensor or gravity sensor, capacitive human body sensor has the characteristics of less auxiliary devices, small size and low cost.

Chip connection

The circuit of the TC301D chip solution is simple. When it is used for human body induction, it is only necessary to short-circuit pins 7 and 8 (FUN, VCC), and short-circuit pins 4 and 5 (CR, CX) to remove the 4-pin capacitor. The correction function can be corrected according to the environment, and there will be no malfunction due to changes in the environment.

The capacitive sensing design principle is that when the chip senses the human body, there will always be a signal output, and the light will go out when the person leaves. The difficulty lies in how to correctly control the sensing distance and range of the floor lamp. If the distance is too small, people will not be able to sense when standing on it. If the distance is too large, the induction will malfunction. It is a relatively simple and efficient way to use the back-shaped winding method. Of course, the induction antenna can also adopt other structures, such as large-area metal foil and so on.

The vertical sensing distance of the chip is 6-7 cm, and the horizontal sensing distance is 2-3 cm. The density and length of the windings are not fixed. The greater the winding density, the longer the sensing distance, which can be adjusted according to the actual situation.