24-08-2011, 09:57 AM
While driving on highways motorists should not exceed
the maximum speed limit permitted for their vehicle. However, accidents keep occurring due to speed
violations since the drivers tend to ignore their speedometers. This speed checker will come handy for the highway traffic police as it will not only provide a digital display in accordance with a vehicle’s speed
but also sound an alarm if the vehicle exceeds the permissible speed for the highway.
The system basically comprises two laser transmitter-LDR sensor pairs, which are installed
On the highway 100 metres apart, with the transmitter and the LDR sensor of each pair on the opposite sides of the road.
displays the time taken by the vehicle in crossing this 100m distance from one pair to the other with a resolution of 0.01 second,from which the speed of the vehicle can
be calculated as follows:
Speed (kmph) =Distance/Time
0.1 km /
= (Reading×0.01)/3600
or
Reading (on display) =36000 / Speed
Parts list
Semiconductors:
IC1-IC5 - NE555 timer
IC6- IC9 - CD4026 decade
counter/7-segment
decoder
IC10 - CD4011 NAND gate
IC11 - 7812 12V regulator
D1, D2 - 1N4148 switching diode
D3-D6 - 1N4007 rectifier diode
LED1 - Green LED
LED2, LED3 - Red LED
DIS1-DIS4 - LTS543 common-cathode,
7-segment display
Resistors (all ¼-watt, ±5% carbon):
R1, R4 - 100-kilo-ohm
R2, R5, R6,
R8, R10,
R11, R14 - 10-kilo-ohm
R3, R7, R13,
R16-R19 - 470-ohm
R9 - 470-kilo-ohm
R12, R15 - 1-kilo-ohm
VR1, VR2 - 100-kilo-ohm preset
VR3 - 20-kilo-ohm preset
Capacitors:
C1 - 100μF, 25V electrolytic
C2, C4, C6,
C8, C11 - 0.01μF ceramic disk
C3, C13, C15 - 0.1μF ceramic disk
C5 - 10μF, 25V electrolytic
C7 - 0.47μF, 25V electrolytic
C9 - 0.2μF ceramic disk
C10 - 1μF, 25V electrolytic
C12 - 47μF, 25V electrolytic
C14 - 1000μF, 35V electrolytic
Miscellaneous:
X1 - 230V AC primary to 0-
15V, 500mA secondary
transformer
PZ1 - Piezobuzzer
LDR1, LDR2 - LDR
S1, S2 - Push-to-on switch
S3 - On/Off switch
- Pointed laser light