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Car Speed Limit Warnings Circuit

2016-02-19 07:32  
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Speed-limit Alert


R1,R2,R19_______1K   1/4W Resistors
R3-R6,R13,R17_100K   1/4W Resistors
R7,R15__________1M   1/4W Resistors
R8_____________50K   1/2W Trimmer Cermet
R9____________470R   1/4W Resistor
R10___________470K   1/4W Resistor
R11___________100K   1/2W Trimmer Cermet (see notes)
R12___________220K   1/4W Resistor (see notes)
R14,R16________68K   1/4W Resistors
R18____________22K   1/4W Resistor
R20___________150R   1/4W Resistor (see notes)

C1,C7_________100µF  25V Electrolytic Capacitors
C2,C3_________330nF  63V Polyester Capacitors
C4-C6___________4µ7  25V Electrolytic Capacitors

D1,D5______Red LEDs  3 or 5mm.
D2,D3________1N4148  75V 150mA Diodes
D4________BZX79C7V5  7.5V 500mW Zener Diode

IC1__________CA3140  or TL061 Op-amp IC
IC2____________4069  Hex Inverter IC
IC3____________4098  or 4528 Dual Monostable Multivibrator IC

Q1,Q2_________BC238  25V 100mA NPN Transistors

L1_____________10mH  miniature Inductor (see notes)

BZ1___________Piezo sounder (incorporating 3KHz oscillator)

SW1____________SPST  Slider Switch

B1_______________9V  PP3 Battery (see notes)

Clip for PP3 Battery
This article shows that the car speed limit warning circuit. Note that this circuit is not suitable for diesel engines. The circuit works as follows: IC1 form a differential amplifier electromagnetic pulse generated by the engine spark plugs, recipients through the sensor coil L1. IC2A further enlarged, IC2F IC2B pulses and pulse square wave inverter provides clean.  Monostable multivibrator  IC3A as a frequency discriminator, its pin 6 must resolutely high when the speed limit (settled R11) is reached. D3 introduces a small amount of hysteresis. IC3B, transistors and vice component provides timing signal part, by the D5 and piezo sounder BZ1 leadership.


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