This circuit is designed to help minimise the quiescent power consumption of PCs and notebooks, the usage of simply our previous buddy the 555 timer and a relay as the major parts. The circuit itself dissipates round zero.5 W in operation (that is, when the linked PC is on); when switched off (with the relay not energised) the entire power draw is precisely zero. A prerequisite for the circuit is a PC or note e-book with a USB or PS/2 keyboard socket that is energyed best when the PC is on. The power saver can be used to change PCs and even whole multi-way extension leads. The unit can additionally be constructed into an ordinary mains adaptor (which will must have an earth pin!) because the photograph of the creator‘s prototype shows. The PC is plugged in to the socket at the output of the ability saver unit, and an extra connection is made to the keep watch over enter of the unit from a PS/2 (keyboard or mouse) socket or USB port. Only the 5 V provide line of the interface is used.
PC Power Saver Image
When button S1 on the facility saver is pressed the unit turns on, and the monostable shaped by using the 555 timer is brought about by means of the network composed with the aid of R4 and C7. This drives relay RE1, whose contacts close. The connected PC isn't anyw tentatively powered up by means of the relay for a length determined by P1 (approximately in the vary from 5 s to 10 s). If, all through this interval, the PC fails to indicate that it is alive through supplying 5 V from its USB or PS/2 connector (that is, if you don't change it on), the monostable duration will expire, the relay will drop out and any related device will be energyed down. No further current will be drawn from the provision, and, after all, it might not be that that you may imagine to turn the PC on. When-ever you want to have to show the PC on, you must always press the button on the ability saver quickly earlier thanhand.
If, however, 5 V is delivered through the PC to the input of optocoupler IC2 earlier than the monostable occasions out (which will be the case if the PC is changeed on all over that length), the transistor within the optocoupler will conduct and discharge capacitor C6. The monostable will now stay prompted and the relay will stay energised except the PC is changeed off and power disappears from its USB or PS/2 interface. Then, after the monostable time duration expires, the relay will drop out and the power saver will disconnect itself from the primarys. There isn't any want to switch anything else off: just shut down the gadget and the power saver will deal with the stayder.
Circuit diagram :
PC Power Saver Circuit Diagram
It is additionally imaginable to leave the computing device as it replaces its tool, and the ability saver will do its job quickly after the laptop shuts down. Power for the unit itself is obtained using a simple provide circuit based around a miniature transformer. Alternatively, a 12 V mains adaptor can be utilized, so lengthy as a relay with a 12 V coil voltage is used for RE1. In hellos proto-type the author used a relay with a 24 V coil connected as proven immediately to the positive facet of reservoir capacitor C2, the 555 being energyed from 12 V regulated from that sup-ply using R1 and D1. A fixed resistor can of path be used instead of P1 if desired. If the adjustment vary of P1 isn't adequate (for example if the PC energys up very slowly) the monostable period may additionally be elevated via the usage of a larger capacitor at C6. The relay must have at the least two normally-open (or changeover) contacts rated at at least eight A. The contact in parallel with S1 is used to provide energy to the device itself, and the opposite contact carries all of the current for the linked PC or for the ex tension lead to which the PC and peripherals are related.
Pushbutton S1 must be rated for 230 VAC (US: one hundred twenty VAC) operation: this is no place to make economies. The coil current for the relay floats thru LED D5, which must therefore be a 20 mA sort. If a low-current LED is used, a one hundred twenty Ω resistor may additionally be connected in parallel with it to carry the staying current. The Fujitsu FTR-F1CL024R relay used in the creator’s prototype has a rated coil present of 16.7 mA. Optocoupler IC2 offers isolation between the circuit and the PC, and that is protected from reverse polarity connection with the support of diode D4. The power saver must be constructed into an insulated enclosure and great care should be taken to be certain that there is right kind isolation between parts and wires carrying the majors voltage and the other phases of the circuit. In phaseicular, the connection to the PC and related elements (R6, C5, D4 and IC2) must be in moderation arranged with as a minimum a 6 mm hole between them and any section of the circuit at majors potential.
Author : Wolfgang Gscheidle (Germany) - Copyright : Elektor
