According to the rules of the PA rusnoj regatta, before its launch should be started a countdown time. Typically, in preparation for the start of the movement of participants assign offices 5 dog handling competitions or 10 min, isteche Research Institute which should "start" command. It is for the countdown of the five minute interval timer was made prestarting whose description is offered to readers.
The timer scheme shown in Fig. 1. He made the mikrokontrol Lere PIC16F873A-I/SP (DD1). For improving the accuracy of decisions countdown often Ta mikrokontrol clock quartz stabilized re zonatorom Leroy ZQ1. As a display device remaining before the start time used trjohrazrjadnyj led seven-element indie cator with BA56-12SRWA common anode (HG1) red glow with a character height of 14.2 mm. Nourish the microcontroller and the indicator through the integrated voltage +5 Analyzer in re-establishing a 7805 (DA1). He additionally secured to the motherboard screw with nut and washer. These details serve and the heatsink.
Signals from the outputs of the RB0-RB7 micro controller come on cathode diode light indicators. Resistors R7-R14 limit current elements. Signa LY with outputs RA0-RA2 manage bipolar p-n-p transistor VT2-VT4 (2N3906), designed to help turn indicator HG1 anodes to the supply circuit.
The sound emitter 1 with built-in s ' generator controls on signals of the microcontroller transistor VT1 (2N3904). To increase the volume of the sound this site eats unstabilised voltage 12 v.
Immediately after power on displays indicators measure Tai co bination of 5.00 (5 min 0000). Countdown time begins from the moment you click SB1. At the end of each MI chickpeas emitter 1 gives a short beep. During the last minutes of the interval signal zauchit every 10 s, and in the last 10 with the timer it em beeps every seconds. Upon completion of a timer dit moves account to its original state and to his indie kator 5 min is displayed again with 0000. He is ready for a new start.
The signal for the start of training judges serves twice, for 5 min and for 1 min before the start of the race. It happens that members of Equipo MS for one reason or another, zapazdy ing with push button start Ty measure on the first signal. In this case, the second signal on the button should be pressed again. If interval has not expired, the timer will start a new countdown with 1 min with 0000.
Details timer mounted on ne chatnoj Board (Figure. 2size 70 x 63 mm). Board is made of foil-clad with one hand steklotekstoli TA 1.5 mm thick. SB1 button can be any without fixing down with standing in wash-down performance.
Fig. 2
Плата должна быть помещена в водонепроницаемый корпус. Для повышения контрастности изображения индикатор можно закрыть автомобильной тонировочной плёнкой. В качестве источника питания можно использовать батарею напряжением 9…12 В. Необходимо предусмотреть не показанный на схеме выключатель питания.
Properly built device forge does not require. Just prior to installation of the microcontroller to charge record in his memory the program. I then microcontroller PIC16F873A-1/SP you can apply PIC16F876A-1/SP.
Author: V. SUROV, Gorno-Altaisk
Source: Radio No. 4/2017
