How to make a automatic light on from the old power supply for computer

Do not rush to dispose of old computer parts. They still serve — for example, to create additional intelligent lighting network in the country.

To create a system of emergency lighting is not difficult. The system is semi-automatic, during Assembly, we use low voltage led bulbs from 1 to 15 W switching power supply with output voltage 12 VDC, adapter for installation in bases lamps with E27 socket GU10 or MR16.

Such an adapter recently went on sale. Lampshades most lamps reliably hide this team structure and the dimensions of the adapter installed, the led lamp is almost equal to the normal incandescent lamp is 25 watts.

Lamps with socket MR16 and GU10 is designed for dual voltage — 12 and 220 V, lamp with socket E27 available only under the standard voltage is 220 V.

To convert AC mains voltage of 220 V to DC 12 V required switching power supply. Led lamps of more than 3 W is very sensitive to the pulse voltage. As shown, when powered by a pulsed voltage of high-power LEDs used in these lamps degrade quickly lose brightness, and some may even explode in a few hours, as the permissible reverse voltage is calculated only by hundreds of millivolts.

Switching power supplies need to connect between the lamp and the network so that the switch is in the high voltage circuit.

The power supply it is recommended to choose at least 10-96 margin of the load that is connected to it. For example, the power supply is supposed to be used in conjunction with a chandelier from 5 led bulbs with 9W each, then you should choose a switching Converter with a capacity of at least 50 watts.

Converters of such power to work with led lamps or strips are commercially available, only are rather expensive. And with the growing power of the price increases exponentially.

Hardware costs can be drastically reduced if to use a pulsed power supply from a personal computer.

It is IMPORTANT the Cost of power supply of led bulbs — from 1 500 rubles. For the supply of led bulb suitable "substandard" power supply, which is on tires +3.3 V and +5.0 V, connected to the processor, transients occur. This is the most common reason for replacing the computer power supply. Bus +12 V voltage is correct and it is suitable for power led lamps.

Computer power supply consists of a power Converter, which is activated when applying a low logic level to the control input and the low voltage source of the duty voltage. To the source of a duty voltage, you can connect any device that controls the operation of the power unit.

Thus, it becomes possible to implement a number of service functions:

  • automatic switching of lighting at dusk;
  • remote control via radio or IR remote controller;
  • presence sensor (so-called PIR-detector), which includes coverage in the presence of people and turns off the light in the empty room.
I decided to make a device that turns the light on at dusk. The switch is made on the basis of the integral timer NE555. The timer is operating in the mode comparator compares the voltage on the external divider R1R2 with a voltage from internal resistive divider, the built-in timer, and as soon as this voltage is less than 1/3 of the supply voltage, changes the logic level at the output 7 from high to low. A low level on the bus PS-0N launches powerful power Converter switching power supply unit and the output of the power supply voltage appears +12 V. an Indicator of a twilight switch is a led HL1, which is included in the operating mode and disabled when the system is in standby mode.

Twilight switch is powered by the source of the duty voltage and draws less than 10 mA.

Through the use of the integral timer scheme was simple and compact. It contains 4 resistors, a timer, a led and a condenser which are placed on the PCB size 60 x 42 mm.

For connection to computer power supply it is recommended to use the standard 20-pin power connector, borrowed from outside the motherboard of a personal computer.

On the one hand, the use of this connector enables you to quickly change the control unit, for example when it breaks or upgrading, on the other — provides a comfortable mounting system as a whole.

You can, of course, solder the wires from the computer power supply directly to the Board, if you can't find a suitable plug. The above chart shows color coding of wires from the power connector of the power supply, which are connected to the twilight switch.

Before system installation it is necessary to test it. To do this, cover the photoresistor with electrical tape or put on his opaque housing. Connect the twilight switch to impulse power unit of a personal computer.

To one of the power rails with a voltage of +12 V between yellow and black wire) turn the load — halogen lamp with a capacity of at least 20 W or 3 led bulbs at 9 watts each.

Connect the power supply to the network. Lamp (or lamps) should be ignited from the running power supply. Now remove the light isolation characteristics of the photoresistor.

The lights go out, the power supply will turn off and the led will turn off HU, placed on Board the twilight switch indicating the unit is now in standby mode.

This scheme has a low sensitivity whereby small changes of illumination do not lead to chaotic switching on and off of the load.

As you can see, the system is simple, compact, versatile and convenient. It can be set in a city apartment or a country house, and used for low-voltage stationary systems of Park lighting or for lighting the pool.

Fig. 1. Adapters for cartridges E27: left — for lamps with GU10 base; right — MR16.

Fig. 2. Connection diagram low-voltage power supply to the lamp. Diode, biased in the reverse direction, disconnect the battery in the presence of the output voltage pulse inverter. The switch in the circuit allows the battery to switch on the lights in the absence of mains voltage.

Fig. 3. Switching power supply personal computer power 300 watts.





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