The article "Soft"load on the grid ("Radio", 1988, № 10, p. 61) describes a device for "smooth"the load connections to AC power. Such devices can successfully be applied for switching of electrical appliances. As is known, the resistance of the filament of an incandescent lamp in the cold state is much less than in hot. That's why incandescent bulbs often fail at the moment of inclusion.
The soft connection of the lamp current through the filament is increased gradually, not reaching the extreme values, so long eternity lamps immeasurably. However, the implementation of these devices involves a number of difficulties. First, it requires the use of capacitors of large capacity, which for security purposes shall be designed for a voltage of less than 400 V. This leads to a substantial increase in the size of the device. Secondly, the fact that the switch built into the device itself, makes to lay additional lead wire.
In many cases, this complicates the design, so as to benefit from the ready switch of the light fixture. (for example, floor lamp or chandelier with a button mounted on the cord) is usually impossible. To circumvent these difficulties allows the device described below. It (see diagram) is in the form of dopoluchila. This allows you to place a charge with its parts in any convenient place, including a broken wire connecting the switch SA1 (suitable existing lighting in the instrument) with the lamp HL1 (or a group of parallel connected lamps). The device allows the combination with a wall switch - can be "hidden"inside the chandelier, it does not need any
The use of the transistor KTA, having a large static current transfer ratio and a significant capacity, has enabled us to do the capacitor C 1 is relatively small capacity. Besides this transistor (it is used in the electronic switch 36.37.34 contactless ignition system of cars "Samara"and "Tavria") it is not difficult to acquire in shops of automobile spare parts. He belongs to the so-called "compound", so it can run with a relatively small base current, which gave the opportunity to use a resistor R1 a fairly large resistance and thus reducing the capacitance of the capacitor C1. This has reduced the size of the device.
Under these scheme types and values of components, the length of the delay switching on the lamp HL1 equal to approximately 100 MS and off - time of 5 MS. This assures the gradual heating of the filament of the lamp at any possible character switching current switch SA1. By the way, set the time delay lamp completely invisible, visually ignition of the lamp will be still almost instantly.
When the lamp power to 100 watts transistor VT1 can be mounted without heatsink. When a larger value (maximum power 300 W) will require a small heat sink. Diodes CDC can be replaced with others of the same series with beech-state index from L to S. In some cases structurally, it is more convenient to use a diode matrix To C, suitable for voltage and current. The described device is operated by the author in relatively light chandelier for several years, and during this time have not needed to replace any of the lamps.
If necessary, switching of the lights even greater power as a protective device, you can use the trinistorny power regulator, assembled one of the known schemes. Variable resistor regulator must be replaced by a circuit which is shown here on the diagram between the common point of the cathodes of the diodes VD1, VD3 and common point of the anodes of diodes VD2, VD4; the diodes are not needed. Wherein the working voltage of the capacitor can be reduced, and the transistor VT1 can be replaced by a low-power low-voltage, but with possible large current transfer ratio. It is only important that they be designed for a voltage stabilizing Zener diode, typically used in power controllers with phase - pulse control. The lamp HL1 should be included in the AC circuit (in series with a diode bridge or a triac).
Author: V. Bannikov, Moscow; Publication: N. Bolshakov, rf.atnn.ru