Dot-Matrix Large-screen speech induction meter--body induction

Dot-matrix screen or relatively power consumption, and the content of the display, in the minimum brightness of the conditions, measured average about 130mA. In order to save energy, prolong the use of battery power, the introduction of the human body Induction switch module, in the absence of detection of personnel activities in the case of turning off the screen display, single-chip microcomputer into the power-down mode. Theoretically is relatively simple, but in the implementation of the process encountered a lot of problems, recorded and shared with everyone.

Question 1, supply voltage

In order to facilitate the use of lithium batteries, the system uses 3.3V voltage, but the online purchase of human induction Switch module is 5V power supply. Fortunately, carefully read the module data, the circuit on the module is 3.3V, the board with a AMS1117 voltage regulator chip to convert the external 5V to 3.3V use, so it is easy to remove the 1117 chip can be transformed into 3.3V power supply.

Issue 2, STC12 series external interrupts only support falling edge/low level trigger, and the sensing module is active high level

This is not an unresolved problem, the latest STC15 series microcontroller support rising edge trigger, can be used directly. But I want to use the ready-made STC12 SCM module, you can only think of another way, that is to use transistors to make an inverting circuit.

Vcc━━━━━━━━┳━

█1k

┣━━p3^2

Inductive output ┃

━━██━━━━≤s8050

10k┃

Gnd━━━━━━━┻━━

Simple drawing of a circuit diagram.

Question 3, the first induction trigger normal, the next few times prone to failure to trigger the situation

4. After the system enters the drop point mode, the external interrupt is automatically triggered after half a second.

Dot-Matrix Large-screen speech induction meter--body induction