The main difference between this power supply from a "typical" network adapter that it can disconnect from the network after some time after switching on. This time installed smoothly (variable resistor) in the range from 10 minutes to 2 hours. The unit can be used where you need to turn off any battery equipment powered from the AC adapter, after some time, a large precision installation which is not required. For example, many people like to fall asleep the music or listening to the radio. So the receiver is not crowed all night, it can to disable this timer. Diagram of a "typical" network adapter shown in Fig. 1.
Fig. 1
Such sources for equipment battery powered most often in sale. There is nothing except the transformer and rectifier with a smoothing the capacitor. Of course, this the adapter is desirable to Refine, to make adjustable stabilizer on CRAN or another chip. But in this article talking about the other.
Schematic diagram of the adapter, supplemented by the timer shown in Fig. 2.
Fig.2
In the gap of one of the conductors of the primary winding of the transformer pad included the switch S1 and the relay contacts K1.
If you are not going to use the timer - switch S1 and use adapter as usual. To use the timer, you need to enable the adapter to the network as usual, then to turn on and off S1. This will start the countdown, and then, its expiry, the adapter will turn off completely. Accordingly, switches off and load.
At the time of power-on is forced to reset counter D2.
Zero with his 14-year discharge (Q14) is inverted by inverters D1.5-D1.6 and the voltage high level with their outputs opens the transistor VT1, the relay K1 closes the contacts. Now if you turn off S1 voltage will pass through the relay contacts.
From the moment you turn the countdown begins, set a variable the resistor R3. The pulses from the generator output D1.1-D1.2 (whose frequency depends on R3) considers the counter D2. After some time, which may be from 10 to 120 minutes, depending on the resistance R3, the output Q4 of the counter appears unit, and, therefore, the outputs D1.5-D1.6 will be zero. The transistor is closed and the relay disconnect the AC adaptor from the outlet.
The remaining two extra elements of the chip CD4069A made indicator led HL1 flashes, and the frequency of blinking depending on the time (the more time, the lower the frequency of blinking).
Electromagnetic relay TRG5-9VDC-FA-CL, in a small package sizes only 12x8x10 mm (such relays are used in some computer modems). Contacts relay rated current up to 0.25 A at a voltage of 220 V.
The relay coil 9 V. you Can use another miniature electromagnetic relay settings are not worse than this one.
Chip CD4069A can substitute for another HHH or domestic K561LN2. You can use CD4049, but she has a 16-lead package Pinout and other. the 14 bit counter NJM4020B - full analogue of domestic CAA. Can use a CD4020 or any other IC HHH and counters CIE, ACREE and other analogues.
The establishment lies in the scale markings, worn around the handle of the resistor R3, time units.
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