The picture above is an automated ice circuit for the windshield of a car cab. As a passenger, I personally witnessed the thick ice on the car glass, opaque, the driver could not shovel with the shovel, causing the bus to stop for half a day. In order to solve this problem, this circuit is designed in this example. When the glass freezes or frosts, the ice and snow are automatically melted to ensure that the driver's line of sight is clear and avoid accidents. This circuit can also be used in other locations where dehumidification is required.
In the figure, Rs is a heating resistance wire, which is placed on the icing window glass, as shown in Figure 7-68a. H is an icing humidity sensor, and T68b is a Schmitt trigger circuit for controlling the electric monument R transistors VT1 and VT2. The collector load of VT2 is the coil winding of relay K. Ri, R: is the base resistance of VT1, and RD is the equivalent resistance of the humidity sensor H. When not freezing, adjust the resistance values ​​so that VTI is turned on and VT2 is turned off. Once frozen, the equivalent resistance RD of the humidity sensor H drops to a certain value, R2∥RD decreases, VT1 is turned off, VT2 is turned on, and the VT2 collector load relay K coil is energized, its normally open contact 2 Turn on the heating power supply E, and the indicator light is on. The relay is always connected and the contact is turned on. The electric heating wire R is energized, and the ice and snow on the windshield are heated and melted. When the melting is completed, RD∥Rz returns to the resistance when it is not frozen. VT1 and VT2 are restored to the initial state, the indicator light is extinguished, the resistance wire is de-energized, and the heating is stopped, thereby realizing automatic ice control.
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Phone Holder , Phone Stand
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