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Digital radar speedometer(74AS04)

2015-01-10 00:13  
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This article describes the Digital radar speedometer (74AS04). The content is very simple, very practical. The components of the article can help you understand better grasp this principle. For example, in this part of the principle, you can go to find and purchase the components: 74AS04.

?Digital radar speedometer


Digital Radar Speedometer th Digital radar speedometer

This circuit is a Digital Radar Speedometer. It allows us to
evaluate the speed of any object moving, especially cars and
other vehicles. The speed is calculated in kilometers per hour
(KPH). Its display has three digits. This radar works with the
laser reflexion. It sends laser radiation to the object and
this object reflects the laser radiation to the radar. To
evaluate the speed of a vehicle, we must be in front of it. In
other words, the vehicle must come in our direction. The front of
the radar must point the front of the vehicle. The radar has the
shape of a pistol. In this radar, it has a laser LED and a laser
diode. Both have a lens.

The laser LED can send a spot of light to a distance of 90 m
(295 ft). It`s very important that the distance range of the
laser LED is 90 m, if not, the speed will not be calculated
properly. The laser diode, which receives the light signal by the
laser LED, must be able to detect the light which is same color
as that emitted by the laser LED. The laser diode and the laser
LED must be placed one beside the other. They are protected
by a tinted pane. They must be placed at the front of the radar
and point the outside. The radar is powered by a 9V battery and
it has a SPST switch to control its power state.

The display, or the speed indicator, is placed at the rear of
the radar, just on the right of the overload LED indicator. All
the logic components of the circuit must be of the 74AS series
and TTL type. Because they have short time of response (less than
1.7 ns) and have high frequency supports (more than 200
MHz). The radar can evaluate the speed of an object moving
betw1een 0 to 999 km/h. After this speed, the overload LED
indicator will turn on and the “999″ will still displayed. The
radar displays the speed during 3 seconds, after this time, it
displays “zero” (0).