Showing posts with label cars. Show all posts
Showing posts with label cars. Show all posts
Tuesday, September 9, 2014
Rear Fog Lamp For Vintage Cars Wiring diagram Schematic
According to current legislation in many countries, vintage cars must also be fitted with a fog lamp at the rear. In modern cars, there is a bit of schemary associated with the fog lamp switch to prevent the fog lamp from going on when the lights are switched on if the driver forgot to switch it off after the last patch of fog cleared up. The schema described here extends that technology back in time. The schema is built around a dual JK flip-flop (type 4027). T3 acts as an emitter follower, and it only supplies power to the schema when the lights are switched on.
For safety reasons, the supply voltage is tapped off from the number plate lamp (L2), because it is on even if you accidentally drive with only the parking lights on. The wire that leads to the number plate lamp usually originates at the fuse box. As the states of the outputs of IC1a and IC1b are arbitrary when power is switched on, the reset inputs are briefly set high by the combination of C1, R1 and T1 when the lights are switched on (ignition switch on). That causes both Q outputs (pins 1 and 15) to go low. IC1a and IC1b are wired in toggle mode (J and K high).
The Set inputs are tied to ground (inactive). The driver uses pushbutton switch S1 to generate a clock pulse that causes the outputs of the flip-flops to toggle. The debouncing schema formed by C2, R4 and T2 is essential for obtaining a clean clock pulse, and thus for reliable operation of the schema. C1 and C2 should preferably be tantalum capacitors. The Q output of IC1b directly drives LED D1 (a low-current type, and yellow according to the regulations). The Q output of IC1a energises relay Re1 via T4 and thus applies power to the rear fog lamp L1.
Rear Fog Lamp For Vintage Cars Circuit Diagram
Free-wheeling diode D2 protects T4 against inductive voltage spikes that occur when the relay is de-energised. In older-model cars, the charging voltage of the generator or alternator is governed by a mechanical voltage regulator. These regulators are less reliable than the electronic versions used in modern cars. For that reason, a Zener diode voltage-limiter schema (D3 and R9) is included to keep the voltage at the emitter of T3 below 15 V and thus prevent the 4027 from being destroyed by an excessively high voltage.
The supply voltage for the schema is tapped off from the fuse box. An accessory terminal is usually present there. Check to make sure it is fed from the ignition switch. The pushbutton switch must be a momentary-contact type (not a latching type). Ensure that the pushbutton and LED have a good ground connection. Fit the LED close to the button.
The following ‘Bosch codes’ are used in the schematic:
- 15 = +12 V from ignition switch
- 58K = number plate lamp
- 86 = relay coil power (+) IN
- 85 = relay coil power OUT
- 30 = relay contact (+) IN
- 87 = relay contact OUT
Author: Eric Vanderseypen - Copyright: Elektor Electronics Magazine
Tuesday, September 2, 2014
Dome light dimmer for Cars
This unique schema makes your dome light look cool. Usually when the car door is closed, the dome light just goes OFF. With this schema, you can have our dome light fade slowly in brightness and finally go OFF. This slow dimming of the light gives a very good feeling at night. It looks very romantic!
The schema can be explained as follows: When the car door is open, the push to off switch of the door is ON and hence it charges the 22uF capacitor fully. The opamp is acting as a voltage follower and its output is same as the voltage across the capacitor, which is 12V when the capacitor is fully charged. Due to a high voltage at the output of the IC, the transistor saturates, turning ON the bulb to full brightness.
Now when the door is closed, the door switch is pushed in and hence the switch goes OFF. When the switch is OFF, the capacitor starts discharging slowly through VR1 and the 10K resistor and the voltage across it decreases slowly. Hence at the output of IC 741 also the voltage decreases gradually, hence decreasing the base current to the transistor. This produces a slowly decreasing current through the bulb and the bulb fades out and finally when the capacitor is fully discharged, the bulb goes OFF.
After building the schema, with the push-to-off switch in ON position (not pushed in) i.e. the car door open, adjust the preset VR2 to the required initial brightness of the bulb. Then push the switch in to turn it OFF(or close the door) and adjust VR1 for the time to bring the bulb from full brightness to OFF.
I would suggest you set VR1 and VR2 to their maximum values.
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