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) In this device, when the car door is opened, the light of the interior lighting lamp lights up smoothly in 5 seconds, burns 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 the trade network IRFZ44.

All necessary vehicle wiring pins are located next to the vehicle 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 the electrical circuit for connecting the interior lighting lamp may differ for different car models, 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 a simple circuit of the turn-off delay and smooth dimming of the 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 in parallel with 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 mains board), 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 the visual effect of smoothly turning off the interior lighting will be created. 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 the case of using not incandescent lamps in the illuminator, but LED bulbs will require a smaller capacitor capacity and a resistor that "extinguishes"... 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.

Many people like the smooth dimming of the light in the cabin, but not all cars have this function. In this article, I will explain how to assemble a circuit for smoothly turning off the light in the cabin with a delay of 3 seconds... The scheme was created for a Daewoo Lanos car, the colors of the terminal block are indicated specifically for this model.

In parallel with the addition of a smooth shutdown function, it was decided to replace the standard interior lighting bulb with its LED Chinese counterpart, which emits much less heat, which, as you can see in the photo, “crumbles” the plastic of the ceiling.

Scheme of smooth switching off of interior lighting of Daewoo Lanos with a delay

The scheme is simple and does not require any special explanations. On the first transistor, a turn-off delay is organized. A capacitor and a 1M resistor connected in parallel serve as a time-setting circuit; the higher the capacitance of the capacitor and the resistor value, the longer the lamp turn-off delay. When the “switch” output is connected to the ground wire using the “slide” switch, the capacitor capacitance is instantly charged through a resistor of 5 (kOhm). The diode after the resistor is not installed accidentally. When the doors are opened, ground is supplied to the gray wire of the terminal block, and (as it turned out as a result of experiments) when the door is closed, the earth not only disappears, but +12 volts comes to replace it. It was for the purpose of blocking the subsequent positive potential, which instantly discharges the capacitor's capacity, that a diode was added to the circuit. The second transistor (kt819) acts as an amplifier. The resistor in its base 1 (kOhm) determines the brightness of the glow, when using conventional incandescent lamps, it may be necessary to reduce its value to 300-500 Ohm, as well as increase the capacity of the time-setting capacitor. Pay attention to the resistor connected in parallel with the load, in the case of using LED lamps, it is necessary to "extinguish" the lighting. This is due to the fact that when the voltage at the lamp terminals drops to 7-8 Volts, the current consumption drops sharply and the lamp glows for a long time at 10% incandescence.

I'm going to tell you here about a simple scheme for smoothly turning off the interior lighting in a car. It includes a small capacitor and several auxiliary elements necessary for the operation of this device. Despite the seeming simplicity, the scheme can fit for any car. All that is required for this is to carefully and carefully solder it to the two terminals of the interior lighting plafond.

Now let's dive in more detail on how this circuit should work. The rectifying diode is designed to protect the device from polarity reversal and reliably prevent unexpected current leakage in the opposite direction. This completely prevents accidental discharge of the charged capacitor into the circuit.

It is also necessary to consider that in a number of cars, the interior shade is initially parallel to the luggage light. With a greater current consumption, we will need, respectively, a large capacity, which is used in our device.

From the diode, the current is directed directly to the plafond, as well as to a resistance of 1 Ohm. The main function of the auxiliary resistor is to limit the current strength, which directly affects the charging of the capacitor. If the capacitor connected to the network turns out to be completely discharged, then a sharp surge in current consumption will occur. The capacitor in this case is a potential source of short circuit. This is what can cause a breakdown of the fuse that protects the mains from a short circuit.

Charged capacitor, as soon as the interior lighting is turned off, it slowly begins to give the generated energy back to the network. As the discharge proceeds, the voltage in the lighting circuit decreases steadily. The effect of smooth fading of the light bulb in the cabin is created. Its duration directly depends on the capacitance of the capacitor. The larger the capacity, the slower the light goes out in the passenger compartment. And vice versa.

When replacing conventional light bulbs with LEDs, the capacitance of the capacitor will have to be reduced by adding a "extinguishing" resistor to the circuit. This is due to the nonlinearity of the current drop in LEDs. The fact is that the current passing through the LED is nonlinear when the capacitor is discharged onto it, and therefore the light in the cabin will fade out unevenly. Without such a resistor, the light that goes out smoothly at the beginning at the end will continue to glow for about a minute, maintaining 10% brightness.

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 OOS on the voltage formed by the R1C1 circuit, a voltage of 1.4 ... 1.5 V is set on 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 complete shutdown time depends on the power of the EL1 lamp, the capacitance of the C1 capacitor, 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 p-n-p transistors, 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 SF1 switch of the car. When assembling the structure, I used 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 central 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.