Resistor Chip Arrays
Product name: Countdown Traffic Light DIY Kit
Product model: TJ-56-690
Supply voltage: 5~9V (DC power supply)
Board size: 134*80mm
Note: It's diy kits. Need to solder by yourself.Function Description:
Countdown traffic lights bring a lot of convenience to people travelling, it allows people to accurately determine when the traffic lights change, so it is extremely widely used. Due to the complexity of the countdown circuit, the use of traditional digital circuits is not easy to achieve, this design is precisely the use of digital circuits to achieve a 20-second countdown function, and in the traffic light change 3 seconds before the yellow light flashing function, can remind vehicles and pedestrians to pay attention to play a warning role.
Working Principle:This circuit consists of a pulse generator, counter, decoder, bistable circuit, scintillation circuit, and control circuit. NE555 and components C1, R17, R18, etc. form a second pulse generator to generate counting pulses; CD40192 is a synchronous decimal reversible counter with functions such as clearing and setting. In this circuit, the preset function of the counter is applied. The preset number is set by P3, P2, P1, and P0. P3, P2, P1, and P0 of U3 are sequentially 0010, which is converted to decimal as "2". P3, P2, P1, and P0 of U4 are sequentially 0000, which is "0". When U3 and U4 are combined, the preset number is "20". When D2 and D3 of the control circuit detect the display 00, they output a signal to pin 11 through the triode VT2 and VT1. At low level, the counter reads the preset number "20", and while the digital tube displays 20, pin 11 returns to high level. At this time, under the action of the pulse generator, the count will decrease until "00" is displayed and the preset number "20" is read again; The CD4511 behind the counter is a decoder, which is used to display the binary number outpu