The reason for writing this article was the desire to make another version of a device popular among motorists - a dimmer for smoothly turning on and off the light in the car. (Nomultithumb)

(ads2) B this device when the car door is opened, the light of the interior lighting lamp lights up smoothly in 5 seconds, lights up constantly for 10 seconds at maximum brightness, and then smoothly goes out in 5 seconds. The whole cycle took about 20 seconds.

If, after opening the door, you leave it constantly open, the light will go out by itself after 3 minutes in order to avoid battery discharge.

The initialization of the start-up of the device occurs when the car door is opened, when the driver opens the door, or the passenger exits. In this case, there is a short circuit to the ground of the contacts of the standard door switch to turn on the interior lighting of the car.

If the door remains open for a long time, the circuit starts a timer that limits the duration of the light burning to approximately 3 minutes. When the door is closed, the circuit switches back to standby mode. In this mode, the current consumption of the circuit is negligible, since the microcontroller goes into a "sleep" energy-saving mode of operation.

The circuit uses an inexpensive AVR microcontroller from ATMEL ATtiny13, for clocking, the frequency of the internal RC oscillator is 9.6 MHz.

How to set fuses during programming is shown in the pictures.

Stabilizer IC 78L05 can be replaced 7805 ... Field effect N-channel transistor I used IRFR024N, you can put and 55L03LT, and if there are no such transistors, we can recommend a more affordable one in trading network IRFZ44.

All necessary car wiring pins are located next to the car interior lamp. The wire from the interior lighting lamp from the (-) side of the standard switch is connected to the output of the circuit "3", to the drain of the output transistor, or to the break of this wire. The wire from the door limit switch is connected to terminal "4". The power supply is + 12 volts, respectively, with the wires of the car's circuit "2" going to these connections. And the common wire (-) with the circuit contact "1".

Since have different models For cars, the electrical circuit for connecting the interior lighting lamp may differ, I have given only a general circuit for understanding the operation of the device.

The small dimensions of the device board allow it to be placed in the voids of the space next to the interior lighting lamp. The board must first be placed in a plastic insulated case. The circuit is connected with only 4 wires, so it can be easily and quickly assembled.

For clarity, as a connection option, there is a diagram for connecting the interior lamp in an AUDI 80 car (90s of production). In this case, the standard switch Sa2 must be set to the "on" position.

Today we will tell you how to make a universal scheme for smoothly turning off the light in the passenger compartment of a car on a capacitor with your own hands.

I published earlier, but for some motorists it may seem too complicated to repeat. I decided to publish the most simple scheme delays for switching off and smooth extinguishing of light on the capacitor and several auxiliary elements. This one is suitable for any car, regardless of the manufacturer. All you need to do is solder the circuit across the connection terminals of your interior light.
Let's take a look at how the circuit works. The top diode on the diagram protects the circuit from polarity reversal and prevents the current from flowing back. That is, it prevents the capacitor from discharging to other consumers except for the interior lamp. In some, a trunk lighting lamp is installed parallel to the interior lamp. The more consumers, the greater the capacitance of the capacitor will have to be used to organize a smooth dimming of the light.
Further, the current goes directly to the lamp and at a nominal value of several ohms (1 ohm is indicated on the diagram). Its function is to limit the charging current of the capacitor.
When a discharged capacitor is connected to the vehicle's on-board network, a large current impulse will be observed, since in a discharged form the capacitor is a short circuit, which can damage the fuse corresponding
for the interior lighting circuit. Through this resistor, the capacitor is charged and energy is accumulated in it, which, when the lighting is turned off (the circuit will no longer receive voltage from the board of the network), will begin to give the stored energy through the resistor and a diode connected in parallel to it to our light bulb.
As the capacitor discharges, the voltage across the lamp will drop and a visual effect smooth switching off of interior lighting. The backlight off delay time is determined by the capacitance of the capacitor, the higher the capacitance, the longer the delay.

It should be noted that in in the case of using not incandescent lamps in the illuminator, but LED lamps glasses will require a smaller capacitor and a resistor for "extinguishing"... This is due to the fact that the current consumed when the voltage drops (across the capacitor) is not linear and drops dramatically when the voltage drops to 7-8 volts.
Without an extinguishing resistor, you will see a smooth extinguishing up to a certain limit, and after that the lamp will glow for another minute at 10% brightness.

In this article, we will consider the scheme for smoothly turning off the light in the car interior. This scheme can be suitable for any car, regardless of its brand, since it is not too complicated and requires a simple installation parallel to the contacts of the interior lighting bulb.

Let's go directly to the study of the circuit. At the top of the circuit, we see a diode, which serves as a protective device for the entire circuit, as it prevents pole reversal and changes in current flow. In other words, we can say that the diode prevents the capacitor from discharging from other devices in the passenger compartment and only works with the interior lighting lamp. Sometimes in some car brands, a light switch in the trunk is also installed near the interior lighting switch. In this case, it will be necessary to install a larger capacitor to smoothly turn off the lighting in both light sources, since the more current consumers are in one circuit, the more volume will be required in the capacitors.

When connecting the capacitor to the circuit, check its state of charge, since when discharged, the capacitor plays the role of a short circuit, and when connected to the circuit, it can deform the fuse for lighting in the passenger compartment.

Having installed a capacitor to the circuit, it accumulates a certain amount of energy through a resistor, and when the current is turned off through the on-board power source, the capacitor releases the accumulated energy, which later goes to the resistor and diode, in parallel with which our light bulb is installed.

When the capacitor is discharged, the voltage in the circuit will drop smoothly, due to which the light will slowly go out. You can control the lamp extinction time with a larger capacitor. The larger the volume of the condenser, the slower the light in the vehicle interior will be extinguished.

Please note that when installing the circuit in parallel led bulb, instead of a conventional incandescent lamp, it will be necessary to install a capacitor of a smaller volume and a resistor with an extinguishing system, since too much voltage in the circuit can cause the LEDs to burn out, and the use of a conventional resistor without an extinguishing system will cause the LEDs to go out smoothly, but will shine at 10% brightness for one minute.

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Smooth switching off of the light in the car interior

Many foreign cars have a function to smoothly turn off the interior light. I also wanted to have such convenience in my car. To do this, I assembled a device with two transistors, three resistors, one diode and an oxide capacitor. Its diagram is shown in Fig. 1.

At the moment of opening the standard door limit switch SF1 of the car when the doors are closed, the capacitor C1 is discharged, therefore, current begins to flow along the +12 V circuit, the interior lamp EL1, C1, R1, emitter junctions of transistors VT1, VT2 and the common wire. Transistors VT1, VT2 open. Due to the action of the OOS on the voltage formed by the R1C1 circuit, a voltage of 1.4 ... 1.5 V is set across the transistors, equal to the total at their emitter junctions (capacitor C1 is discharged, and the resistance of resistor R1 is small). The EL1 lamp maintains the voltage of the on-board network (+12 V) minus the indicated voltage drop across the transistors. The lamp is shining brightly.

Capacitor C1 begins to charge, and the current through it decreases. This leads to a decrease in the base and collector currents of transistors VT1, VT2. The current through the EL1 lamp and the voltage across it drop, and it smoothly goes out. The time of complete shutdown depends on the power of the EL1 lamp, the capacitance of the capacitor C1, the resistance of the resistors and the transfer ratios of the current transistors VT1, VT2. In the author's version, it is approximately equal to 5 s. To quickly discharge the capacitor when opening any door, a VD1 diode is installed.

The device can use medium (VT1) and high (VT2) power transistors of any type. In the case of using transistors p-n-p structures it is necessary to change the polarity of the connection of the capacitor C1 and the polarity of the connection of the device to the standard switch SF1 of the car. When assembling the structure, I applied a hinged mounting of the elements, placing the transistors on a small heat sink (Fig. 2). Since the transistors are in active mode for a short time (5s), their installation on a heat sink is not necessary.

A properly assembled device does not require adjustment. If it is necessary to change the time for turning off the light in the passenger compartment, you should select the capacity of the capacitor C1. The larger it is, the greater the delay in turning off the light, and vice versa. You can install the assembled device in any convenient place I placed it in the B-pillar of the car, next to the light switch. Due to the low current consumption in the off state, it does not affect the operation of the burglar alarm, also connected to the door switches.

This device is used to control the interior lighting of the car - slowly turning on and off the lamp at the moment the doors are opened. The device is equipped with two actually independent channels, that is, it is possible to control the front and rear illumination lamp. The operation of the device can be found in the following video.

Description of the operation of the scheme for smooth dimming of light in the car interior

The circuit is based on the inexpensive and popular PIC12F629 microcontroller. Control over the brightness of the lamp glow is organized using PWM. Its frequency is approximately 200 Hz, which is sufficient for LED and incandescent lamps.

If you open one of the rear doors of the car, the rear interior lighting lamp starts to glow, if you close it, the lamp will slowly go out. The front light works the same way, with one difference - the light decays more slowly.

If the driver's door is open, then in this case, the front and rear interior lamps turn on immediately. After closing the driver's door, the front passenger compartment lamp starts to go out 1 second later than the rear one. If the car is started, the speed of turning off the interior lamps is increased by approximately 3 times.

The device is quite simple, it contains neither quartz (clocking comes from an internal generator), nor any other redundant radioelements. The lamp control keys are made on composite transistors for the operation of incandescent lamps. If LEDs are used in lighting, then it is possible to use one transistor, for example S8050, instead of 2 (KT315 and KT817), since LEDs consume significantly less current compared to an incandescent lamp.

In order for the device to work correctly, it is necessary to separate the standard switches in the car doors, in addition to the 2 rear doors. Electrical diagram the modification of the wiring is shown below. If an auto alarm is used, then it is necessary to include three diodes in the circuit, as shown in the schematic diagram.