Controller circuits for running lights. DRL control on a microcontroller

Review of the Chinese LED Daytime Running Lights control unit - LED DRL controller.

Daytime Running Lights should be turned on when the vehicle is moving (for example, when the engine is turned on), but at night they should be turned off (for example, when the headlights are turned on) or their brightness should be reduced to the level of side lights so as not to dazzle oncoming traffic. On the Internet, you can build many options for self-connecting DRLs to implement such an algorithm for the operation of lights, from the simplest, using the car’s standard electrics, to the very elaborate ones, using electronic circuits with integrated logic. In any case, such a connection requires intervention in the electrical system of the machine, and this is not always useful or safe.

It is much easier to connect DRLs through a ready-made control unit (controller) - they can also be found on the Internet without much difficulty: there are options for working with incandescent high-beam headlight lamps, and there are options specifically for working with LED DRL. There are also controllers for working with combined DRLs with turn indicators, costing about 8…10 USD here or in China, but there is - purely for DRLs without frills: on AliExpress for only 3.5 USD It is this controller that our review will be about.

Unboxing and first impressions

After shipment by the seller, the controller from China arrived just 40 days later, as expected for products of this type and size, in a regular parcel package with a bubble wrap. The control unit did not cause any special impressions or emotions: a sealed plastic box the size of a matchbox, wires for connection, a fuse on the power cable - that’s all done decorously and soundly.

Connection

Connecting the controller is simple even for an average person who is not very tech savvy. We connect the output wires “OUT” to the DRLs themselves, the input wires “IN” to the power supply of the on-board network, for example, to the battery: red to “plus”, black to “minus”. The yellow wire is used to control the brightness of the DRLs - we connect it to the “plus” from the low beam. That's all: no shamanism with jumpers and switches, etc. – for everything about everything – 10 minutes with smoke breaks.

Let's check it in action

The principle of operation of the controller is as simple as the corner of a house. If the on-board voltage is higher 13V(with the engine running), the controller turns on the DRL, if the voltage drops below, it turns off the DRL with a delay of about 15 seconds. A small delay, apparently, was made so that the DRLs do not blink in vain if your engine suddenly stalls when starting off or the voltage drops for a short time. In reality, the duration of the pause for turning off the DRL after turning off the ignition can vary from several seconds to a minute, depending on how quickly your on-board voltage decreases when you turn off the engine. If your DRL turns on/off in a different way, this is a reason to show the car to an auto electrician.

The voltage drop on the controller when the DRLs are on was only 0.23V– this is only 1.5% of the total power consumed by the lights.

To control the brightness, the yellow wire was connected to the low beam power supply of the left headlight. When I turn on the low beam, the total power supplied to my DRLs decreases almost 3 times, although visually from a distance of several meters this is not very noticeable. Even with a power of 1 W per lamp, DRLs shine much brighter than side lights.

When working with a connected yellow wire, a strange “jamb” is observed in the behavior of the controller: if before applying “+12” to the yellow wire the lights are turned off (the engine is turned off), after applying “+12” to it, for example, we turn on the headlights, the lights turn on at full power . If you start the engine, the lights will switch to a reduced mode as expected.

According to the current laws of the Russian Federation, in particular, amendments to the traffic rules, any vehicle driving even during the day must have low beam headlights on. In addition, it is permissible to use anti-fog analogues, as well as daytime running lights, instead.

Due to the fact that using head and fog lights for this purpose is associated with a number of disadvantages, the vast majority of car owners prefer to purchase running light modules and install them themselves. In view of this, it’s worth figuring out how to connect daytime running lights with your own hands?

Features of operation

The legislation quite clearly regulates the rules for the use of such elements in the design of a car. According to GOST requirements, the running lights should turn on immediately when the ignition key is turned, and automatic shutdown should occur if the driver has activated the headlights.

In addition, such a standard stipulates that the head lights should be turned on only after the side lights have been fully turned on. The only exception is when they are used to give signals. This must be taken into account if you want to install daytime running lights yourself.

Do-it-yourself DRL connection, has a number of features that must be taken into account to achieve the correct operating sequence and long service life of the module. To increase its service life, it is wise to use a special stabilizing unit designed for LED lights.

However, this measure is aimed only at increasing the operating time of the circuit; without such a block, all elements will function normally.

One of the most common problems m, characteristic of DRL modules, voltage surges appear, which causes overheating of the crystal responsible for the radiation. In this regard, the brightness of the lights gradually decreases, after which they cease to perform their main function.

Connection options

Considering the most common options for connecting DRLs, it is advisable to disassemble the simplest diagram for connecting running lights without using a stabilizer, generator and other additional elements. To ensure that the DRLs are activated when the engine is turned on, it is recommended:

• Connect the positive wire to the positive terminal located on the ignition switch;
• The negative cord is attached to the car body in any place convenient for the owner;
• When you turn the ignition, the DRL will work.

The main disadvantage of such a connection scheme is that the lights operate constantly when the ignition is turned on. Besides, the work of lights in this case, is not coordinated with other car lighting systems, which means that such a connection does not meet the requirements specified in GOST.

The second connection option is much more suitable for this purpose, since it uses the side headlight circuit. The positive wire of the daytime running lights, in this case, is connected directly to the battery. Negative connect with positive side lights, after which the LEDs begin to glow. At the same time, the lamp coil does not burn, which is due to low current consumption.

After activating the side lights, the driver will be able to notice that the DRL potentials are equalized, which leads to the LEDs turning off. As a result, the vehicle's light circuit returns to normal operation. Despite the fact that this scheme works without serious violations, it has a number of disadvantages, which is why it should not be installed.

It is advisable to include:

Since this scheme also does not meet the requirements of the state standard, it will be necessary to consider the simplest option that meets existing standards.

DRL controller

For the vast majority of owners, it seems most acceptable to use a special control unit, which allows you to connect the HDO according to the correct circuit, without the use of relays and other elements. As a result, the connection diagram is simple and safe , due to unique advantages operation of the controller.

These include:

• Stable inclusion of DRLs after starting the engine;
• Guarantees overload protection;
• Supports any type of lights, including LED;
• Does not affect the operation of other nodes.

Daytime running lights control units, in the vast majority of cases, fully comply with the state standard, which allows them to be safely used for their intended purpose. However, some manufacturers may introduce various functions into such equipment, which, despite their usefulness, may not comply with GOST requirements, which means their use is not recommended.

Another advantage of this kind equipment, it is possible to connect it according to a diagram previously provided by the manufacturer. At the same time, it necessarily contains data on the maximum load, as well as other important technical parameters. This allows you to quickly and easily connect DRLs without any experience or special knowledge.

If you do not plan to purchase a special controller, it is advisable to give preference to the connection option via a relay. It involves the use of a 5-pin relay, which will be used in the general DRL connection circuit. Such a scheme allows eliminates any disadvantages inherent in previous options and makes it possible to safely use DRLs without any additional equipment.

Features of connecting the DRL relay:

• 30 to “+” outputs of LED modules;
• 85 on the “+” cord dimensions;
• 86 are assigned to the machine body;
• 87a to “+” ignition;
• 87 are isolated.

To implement such a connection via a relay, you need to acquire connection wires, terminals, cable ties, heat pipes and tools. Among other things, you should consider a way to securely attach the assembled circuit to the vehicle structure.

Some owners prefer use a generator in the connection diagram, which is not recommended in most cases. After all, in order to install DRLs through the generator, you will need to install a resistor. Despite the efficiency of the circuit, its reliability leaves much to be desired.

This is such a tautology. But nevertheless, what is written, according to syntactic, spelling and semantic rules, has the right to life. Author's Note: A controller is an electronics control device; microcontroller is a miniature part of a controller based on an integrated circuit.

If your car is not equipped with standard daytime running lights, and the use of main headlights is too wasteful for you, the Traffic Rules of the Russian Federation allow the use of fog lights to indicate a vehicle during daylight hours.

But this option is rational only if the power of the light bulbs in the fog lights is less than the power of the lamps in the main headlights. If this is not the case, then installing DRLs cannot be avoided. In general, at the moment, the installation of DRLs on a vehicle in use is not mandatory, but by 2016 all vehicles must be equipped with daytime running lights.

As a result, the conclusion suggests itself - definitely install DRLs.

To do this, you can use the services of a specialized auto center, or you can perform this not very complicated operation yourself. Of course, a lot depends on the car (the complexity of removing the dashboard and bumper) and on the origin of the DRL kit itself (factory production or homemade). It should be recalled that independently installed running lights must comply with the requirements of GOST R 41.48-2004 (UNECE Regulations No. 48 and No. 87) or clause 1.3.29 of Appendix No. 5 to the “Technical Regulations for the Safety of Wheeled Vehicles”.

Relay based DRL controller

Most vehicles have standard factory fog lights. But not all drivers use them. The reasons are different: there is no need, the headlights are too power hungry or simply ineffective. So they can be converted into running lights. Naturally, the light bulbs will have to be replaced with LED analogues. This will give good energy savings. energy and, importantly, will allow you to neglect the consumed current when calculating the electrical mnemonic diagram.

Next, you will need to change the standard switching circuit. This is where you will need (with a high degree of probability) to remove the dashboard and bumper. According to workers' reviews, this is done in just over an hour. After gaining access to the on-board electrical wiring, we switch everything as follows:

It is important to ensure the correct operation of the running lights: they must turn on when the ignition key is turned to a position that allows the engine to operate, and turn off when the main headlights or parking lights (dimensions) are turned on for the low/high beam. To do this, the size signal can be taken directly from the button illumination. This way you will never forget to turn off the DRLs. This scheme has been tested by many car owners and has no complaints.

But what to do if in a car, access to the wiring inside the cabin is extremely difficult or even impossible? For a lazy car enthusiast with an inquisitive mind, this will be a real obstacle. We need another solution. Let's consider the following option.

Option on ATmega8

DRL lamps can be purchased separately, without a control module, at a very reasonable price. There are already holes in the bumper (from the fog lights), if not, we cut them out. The entire installation consists of fixing the lamps with four self-tapping screws. It's up to the controller. In the proposed version, we will consider the use of the good “old” ATmega8, an 8-bit microcontroller from Atmel.

By the way, with its help it is also possible to implement additional functions, for example, an indication of the operation of the firewall, which tends to turn off when the car is running. The operating algorithm of the ATmega8 circuit is as follows: if the car is turned off, the voltage on the battery is less than 13.5 V, if it is started, charging is in progress, and the voltage is above 13.5 V.

The running lights turn on automatically.. Of the connections, there are 2 wires to the battery and 2 wires to the DRL. With careful installation, mid-price DRLs will fit very harmoniously into the exterior of the car.

There is also an option for assembling a DRL control controller based on a comparator.

DRL controller circuit on comparator LM358

In this circuit, the comparator is implemented based on a low-power two-channel operational amplifier LM358. The circuit turns out to be very cheap, and besides, there is no need for a voltage stabilizer; the LM358 single-pole power supply is designed for 3 - 30 V, again, saving money. The schematic diagram is below, everything is simple and clear.

Setting up this controller comes down to setting the circuit's response threshold with a trimmer when the generator is operating, i.e. when the voltage in the on-board network is above 13.5 V.

Everything comes together very quickly and works reliably even in severe frost.

A simple controller for DRLs. High beam lamps are used at 30% switched on. Brightness adjustment is carried out using PWM, and the function of smooth switching on of lamps is also implemented.

Version 1
Schematic diagram:

To power the microcontroller, a linear stabilizer L7805 was used (not shown in the diagram).

When you start the engine, the generator and oil sensor lamps go out, you can also turn on the handbrake and if the low/high beam is turned off, the DRL turns on (high beam by 30%, brightness can be changed in the source code). When you turn on the light, the DRLs turn off, to turn the DRLs back on you need to turn off the light, and then turn it on and off again. The circuit is assembled in Proteus, so you can try it.

Printed circuit boards:
Board for one field-effect transistor with parallel connection of lamps:

When connecting lamps in parallel, I advise you to use a more powerful transistor with a lower open-channel resistance, or connect several, otherwise the infection will heat up.

Board for two transistors - independent control of lamps:

This board is useful if you want to create some kind of strobe effect, or simply have the ability to connect to each lamp separately.

Download the Proteus project, printed circuit boards and source code: (downloads: 408)

Version 2
Schematic diagram:

The second version differs from the first only by the addition of an LED, which serves as an indicator that the lamps are turned on. A new printed circuit board was also installed with three field switches connected in parallel to control more powerful lamps.

Printed circuit board:

Download the Proteus project, printed circuit boards and source code for the second version: (downloads: 363)

Version 3
Schematic diagram:

To increase the response speed of the field switches, a driver based on transistors BC547 and BC557 (you can use KT315 and KT361) was added to the circuit, therefore the heating was reduced and the PWM frequency can be increased.

The DRL controller is a device used to monitor the performance of daytime running lights. With the help of this device, more stable and optimal operation of the optics is ensured, which allows optimizing the functionality of the electrical network as a whole. You can learn more about how to build such a device at home from this article.

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DIY options

If you decide to build a daytime running lights controller for your car, then first we suggest you familiarize yourself with several options for manufacturing the device.

Photo gallery “Schemes for manufacturing”

1. Relay-based DRL controller. Many vehicles have standard fog lights, but not all motorists use them. The reason may be the lack of need for operation, high voltage consumption of the optics, or its inefficiency. Alternatively, if necessary, the fog lights can be converted into daytime running lights, only the lighting sources will need to be replaced with diode ones. You will also need to slightly change the standard connection diagram; most likely, in this case you will need to dismantle the bumper and control panel.
   When you can access the on-board network, the connection procedure is carried out according to the diagram above. In this case, you need to ensure the correct operation of the optics - that is, the running lights should automatically turn on when you start the engine and turn off when you turn on the dimensions or high or low beam. To ensure this, the signal from the side lights can be taken from the button illumination, thanks to this you will not forget to deactivate the DRLs.
2. Using ATmega8 board. This option is more preferable if access to the wiring in the car is difficult. The daytime running lights themselves are purchased separately; you do not need a control unit. You need to install the DRL into the bumper yourself; to do this, make the appropriate holes and fix the optics. After completing these steps, you will only have to work with the controller itself.
   It should be noted that this board also allows you to implement other, no less useful functions, for example, indicating the operation of the engine heater. In this case, the operating algorithm will be as follows: when the vehicle is not started, the voltage on the battery will be less than 13.5 volts. Accordingly, when the engine starts, the battery will be recharged, which means that the voltage will be more than 13.5 volts. The DRLs themselves will be activated automatically. To make the connection, two wires must be connected to the battery, and two to the optics itself.

Instructions for manufacturing the DRL regulator

Let's consider the process of making a regulator for DRLs at home in accordance with the diagram above.

The operating logic of this device is as follows - the unit activates the daytime running lights only in this case:

• if the car’s power unit is started;
• if the side lights and high and low beams are turned off.

Actually, these conditions are mandatory and meet all the requirements for the operation of daytime running lights. When you turn on the low beam at night, the controller will automatically turn off the running lights.

To make a block according to the diagram you will need the following elements:

• two bipolar transistors, designated in the diagram as VT1 and VT6;
• three rectifier diode elements, marked as VD1, VD2, VD3;
• two 1 kOhm resistor components R1 and R2;
• you will also need two 5.1 kOhm resistors - marked as R3 and R4;
• one 10 kOhm resistor element - R5;
• one 15 amp fuse and one 10 amp relay, marked K1 in the diagram.

All these spare parts can be purchased at any radio market, in the appropriate store or ordered online. There should be no problems finding the constituent elements of the circuit. The process of manufacturing the device itself should not cause problems - you just need to connect all the elements on the board in the manner shown in the diagram. The connection procedure is carried out using soldering. If you do not know how to solder, then it is better to contact a qualified electrician - any specialist with experience can solder such a regulator without any problems.

When soldering, be careful not to damage the components of the controller, as this may lead to its further inoperability. All parts must be securely soldered, since vibrations may occur when the car moves, and they, in turn, have a destructive effect on any moving elements. Especially when it comes to electronics.

After the device is made, it must be connected correctly:

• DDM - must be connected to the engine fluid pressure controller or to the parking brake;
• the +12 volt output must be connected to the generator device or the ignition switch, in particular, you need to connect it to the contact where voltage appears when the engine is running;
• dimensions - as you might guess, in this case we are talking about the positive contact of the side lights, the specific connection location does not matter;
• GND is the mass or body of the vehicle;
• DRLs are daytime running lights themselves with halogen or diode lighting sources (the author of the video about the connection is Vitaly Novakov).

As for setting up the manufactured controller, this process consists of diagnosing the operating algorithm as a result of applying simulation pulses to it. When 12-volt voltage is supplied to the parking light input, the relay should automatically turn off. It will also turn off if the oil pressure controller input is shorted to ground.

Price issue

If for some reason you do not want to make a controller at home, then you can always buy it on the market or order it on the Internet. Costs may vary by store, with price differences ranging up to 40%. On average, the cost of a DRL controller today ranges from 650 to 1000 rubles.

Video “Review of the DRL controller purchased in China”

The video below shows a detailed overview of the Chinese daytime running lights controller (the author of the video is Sergey Stanevich).