Introduction of touch switch circuit and delay processing of switch machine
Tact switch circuits have been widely used in digital products such as telephones, mobile phones, and electronic dictionaries, with various implementation methods. Generally, RS flip-flops, counters, and 555 integrated circuits can be used. In some practical applications of electric toys, the above implementation methods will increase the complexity of the entire circuit and cannot achieve concise and practical effects.
This article will introduce a method that can be widely used in digital products such as telephones, mobile phones and electronic dictionaries in electric toy circuits, with various implementation methods. Generally, RS flip-flops, counters, and 555 integrated circuits can be used. In some practical applications of electric toys, the above implementation methods will increase the complexity of the entire circuit and cannot achieve concise and practical effects. This article will introduce a simple and stable light-touch single-key switch circuit that can be implemented in a single-chip microcomputer application.
A simple and stable light-touch single-key switch circuit realized in the application. 1. It is not difficult to see in the processing of Vin connection mode, after adopting this kind of control mode, a certain amount of power will be consumed on Q1. One way to reduce power consumption is to connect Vin directly to the battery, which can be flexibly controlled according to the circuit. 2 The function of capacitor C1 For general electric toys, BOD (Brown-downDetection) circuit is inside. This circuit has a low voltage detection function: when the input voltage changes from high to low, the electric toy will automatically reset.
When you want to shut down, press S1, the output of the electric toy is low.
After the button is lifted, Q1 and Q2 are turned off, and the microcontroller is powered off. However, after the BOD circuit of the single-chip microcomputer detects that the voltage of the single-chip microcomputer has dropped suddenly, it will reset the single-chip microcomputer and set the I/O to the pull-up state, Q1 and Q2 are turned on, and the guidance circuit is turned on again. 3 Circuit Principle The DC socket is a DC stabilized power supply chip with a related break control terminal, and the MCU is a single-chip microcomputer.
When S1 is pressed, Q1 and D1 are turned on, and the voltage regulator chip works to supply power to the microcontroller. The electric toy immediately sets the corresponding I/O pin to output high, then Q1 and Q2 are turned on, and the entire circuit enters the working state. Then the single-chip microcomputer sets this I/O pin as an input. Due to the existence of the pull-up resistor R4, Q1 and Q2 are always on. The electric toy always scans the corresponding I/O input state, if S1 is not pressed down, this I/O will always be high. When S1 is pressed again, D2 is turned on, and the electric toy detects that the input of this I/O pin is low, and then the electric toy sets this I/O to a low output state. Q2 is off. If the button is lifted, Q1 will also be off, the voltage regulator chip will not provide voltage for the electric toy, and the entire circuit is in the off state.
Regarding the value of R3 and pull-up resistor R4, some electric toys, such as the AVR series electric toy linkage series, have an internal pull-up resistor Rpu. The resistance pull-up or not can be controlled by the electric toy program, so there is no need for an external pull-up.
In general, the value of R3 should be much larger than R4, otherwise the input voltage Vpin of the electric toy I/O may be lower than the minimum value of the standard input voltage VIH. From the data manual of the linkage series toys, it is found that the value of Rpu is between 20kΩ~100kΩ, and because the minimum value of VIH is about 0.6VCC.
Therefore, R3/(R3+R4)>0.6, take R4=50kΩ, and take R3/(R3+R4)=0.8, so the value of R3 should be in the range of about 200kΩ. The specific R4 can be selected according to actual working conditions. value.
Tact switch on/off delay processing. In some specific applications, such as mobile phones and other digital products, the switch machine needs to be operated with a delay. A simple way to achieve this is that the microcontroller starts counting when the button is pressed, until the button is lifted. Only if this count value is large enough, is it allowed.
BZCN Zhejiang Bozhong Electric Co., Ltd. has many years of production experience in patch tact switches, waterproof tact switches, and illuminated tact switches. The products are produced in accordance with international standards. The research and development and sales are industry-leading, and are widely praised by new and old customers. For more information, please call our service hotline.