LED standby lighting
Often, in different places, lighting is required such as "just not total darkness." For example, the staircase of an apartment building, where you don’t need to look for needles on the floor, and you only need a minimum light to not stumble or be able to get a key in the keyhole. Usually, in such cases, either a 20-40 watt "Ilyich light bulb" or a "economical" 7-9W is screwed in. Incandescent bulbs tend to burn out often, and “economical women ” simply steal from the ground up (I’ve got five from the staircase for 3 years, five of them are screwed up, but it's unpleasant for me to be screwed) . If you need an economical and anti-theft (well, let's say, more protected than just a light bulb) light source, then read on.
For lighting, we will use powerful 0.5-watt LEDs with a 7.62mm caliber (yes, that one) , they are bright enough and they don’t need an external additional radiator, unlike the more powerful counterparts of “stars” of 1-3 Watts each. In my design, four-legged white LEDs 7.62mm 100mA with a scattering angle of 140 ° are used. The voltage drop on the LED will take ~ 3.3V. We will power from 230V. According to Ohm’s law, the damping resistance should be (230V-3.3 * 3) /0.1 = 2200. The power dissipated on it, respectively, will be more than 20W. The resistor, with such parameters, has a very impressive size and, moreover, will be very hot. We will go the other way and use a capacitor as resistance.
Classic circuit with damping capacitor.
From the course of electrical engineering it is known that a capacitor in an AC circuit has a reactance Xc = 1 / (2Ď€fC), where f is the frequency, C is the capacitance of the capacitor. To get the resistance of the capacitor in the region of 2200 Ohm at a frequency of 50 Hz, the capacitance should be C = 1 / (2 * 3.14 * 50 * 2200) = 0.0000014 Farad. or ~ 1.4 ÎĽF. This is a very rough calculation, where the presence of a rectifier bridge and a smoothing capacitor in the circuit is not taken into account. Let's make a margin for strength, taking a current of 75% of the calculated value (the brightness of the LEDs will be enough, and their mode of operation will become more benign), and take a capacitor with a capacity of 1 ÎĽF. Brightness will be sufficient even at 0.68 uF.
ATTENTION! As a damper, I recommend using only special anti-interference capacitors of class X2, for a voltage of at least 250V. Typically, such capacitors are rectangular in shape and there are a lot of all sorts of certificate marks on the case. Using unsuitable capacitors may cause a fire!
A 220 ohm resistor reduces the inrush of current through the capacitor when turned on. After all, a discharged capacitor, at the moment of switching on, has a very small resistance and, through the whole circuit, for a split second, a very large current flows. Additionally, to protect the LEDs from inrush current at the time of switching and during operation, the circuit includes an electrolytic capacitor and a powerful Zener diode.
Layout "on weight":
For the manufacture will need:
ATTENTION! When operating the device, all elements of the circuit are under life-threatening voltage! Observe safety precautions and caution! Even when completely disconnected from the network, the capacitor saves a charge for a long time. If you touch his conclusions, you can get an unpleasant electric shock. In parallel with the quenching capacitor, you can connect a resistor of 500KΩ - 1MΩ, it will discharge the capacitor when it is turned off.
This device illuminates my staircase for three months and did not cause complaints.
Used materials:
1) Biryukov S. Calculation of a network power source with a damping capacitor - Radio magazine, 1997, Nr. 5, s. 48 - 50.
For lighting, we will use powerful 0.5-watt LEDs with a 7.62mm caliber (yes, that one) , they are bright enough and they don’t need an external additional radiator, unlike the more powerful counterparts of “stars” of 1-3 Watts each. In my design, four-legged white LEDs 7.62mm 100mA with a scattering angle of 140 ° are used. The voltage drop on the LED will take ~ 3.3V. We will power from 230V. According to Ohm’s law, the damping resistance should be (230V-3.3 * 3) /0.1 = 2200. The power dissipated on it, respectively, will be more than 20W. The resistor, with such parameters, has a very impressive size and, moreover, will be very hot. We will go the other way and use a capacitor as resistance.
Classic circuit with damping capacitor.
From the course of electrical engineering it is known that a capacitor in an AC circuit has a reactance Xc = 1 / (2Ď€fC), where f is the frequency, C is the capacitance of the capacitor. To get the resistance of the capacitor in the region of 2200 Ohm at a frequency of 50 Hz, the capacitance should be C = 1 / (2 * 3.14 * 50 * 2200) = 0.0000014 Farad. or ~ 1.4 ÎĽF. This is a very rough calculation, where the presence of a rectifier bridge and a smoothing capacitor in the circuit is not taken into account. Let's make a margin for strength, taking a current of 75% of the calculated value (the brightness of the LEDs will be enough, and their mode of operation will become more benign), and take a capacitor with a capacity of 1 ÎĽF. Brightness will be sufficient even at 0.68 uF.
ATTENTION! As a damper, I recommend using only special anti-interference capacitors of class X2, for a voltage of at least 250V. Typically, such capacitors are rectangular in shape and there are a lot of all sorts of certificate marks on the case. Using unsuitable capacitors may cause a fire!
A 220 ohm resistor reduces the inrush of current through the capacitor when turned on. After all, a discharged capacitor, at the moment of switching on, has a very small resistance and, through the whole circuit, for a split second, a very large current flows. Additionally, to protect the LEDs from inrush current at the time of switching and during operation, the circuit includes an electrolytic capacitor and a powerful Zener diode.
Layout "on weight":
For the manufacture will need:
- small razvetkorobka (case)
- 3 LED 0.5 Watt 100mA
- diode bridge for voltage not less than 400V and current 1-2A)
- 5-watt zener diode 14-15 volts (this stock does not hurt)
- Electrolytic capacitor 100µF for voltage 100V
- capacitor (class X2) 0.68-1 ÎĽF for a voltage of at least 250V
- A resistor of 1-2 watts per 150-200 ohms.
- 1-2 Ampere fuse (for every fireman)
- terminal block
ATTENTION! When operating the device, all elements of the circuit are under life-threatening voltage! Observe safety precautions and caution! Even when completely disconnected from the network, the capacitor saves a charge for a long time. If you touch his conclusions, you can get an unpleasant electric shock. In parallel with the quenching capacitor, you can connect a resistor of 500KΩ - 1MΩ, it will discharge the capacitor when it is turned off.
This device illuminates my staircase for three months and did not cause complaints.
Used materials:
1) Biryukov S. Calculation of a network power source with a damping capacitor - Radio magazine, 1997, Nr. 5, s. 48 - 50.
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Source: https://habr.com/ru/post/164427/
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