12V car icing alarms

 

As long as the temperature of the air near the ground close to 0:00, the alarm circuit will be prompted to car's drivers may be icy pavement this information. Operational amplifier A1 constituting the voltage level of the sensor cable. Operational amplifier A2 is wired as a non constitutes astable multivibrator, in which the current buffer by TRL, filament lamp flashes at about 1Hz. As temperatures drop, reaching a point when the voltage is higher than a foot voltage pin 2.

A1 is driven by the output immediately to positive saturation to operate open loop. A2 were positive output voltage of this power to start the oscillator, and its operation is the V pin 9. Thermal resistance is a resistance type of glass beads of about 20? At 20 ° C. Adjust VR1, the light starts flashing, lattice-type air temperature is 2 ℃.

 

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