Not to forget to turn off the TV, tape recorder, radio, and leaving the house to de-energize electric heaters, collect offer a watchdog timer. Its feature is that the time delay is constant and equal to one hour. If you don't switch at the moment the toggle switch on the motor, the relay will disconnect electrical or electronic devices. Have time to do - will begin to count up the shutter speed.
Watchdog timer (see figure) consists of two blocks. In one of them includes plug X1 socket x2 "Load" for load connection and the fuse F1. Another node - the actual time relay, collected on the thyratron MTH-90 (V2). The load is connected to the network via the switching contacts building 1.1 relay K1. The blocks are connected by a long three-wire cord, thereby providing remote control of the load.
Fig.1. Watchdog timer
When you first turn on the watchdog timer in the network, the switch S1 must be specified in the scheme position. The load will be supplied with mains voltage, the capacitor C1 is quickly charged through the diode V1 and the voltage divider R1R2 to voltage 160... 170 V, and the capacitor C2 begins to charge through the high-ohmic resistor R3. After about an hour the voltage on the capacitor C2 will rise so that will ignite the thyratron. The capacitor C1 is discharged through it and the relay coil K1. The relay will, will disable the contacts K1.1 the load from the network and stand on the switch by shorting the same pins findings of the anode and cathode of the thyratron. Through the relay coil will flow to the holding current is determined by the resistance of the resistor R1. In this state, the watchdog relay can be arbitrarily long.
To avoid disconnecting the load from the network, it is necessary, without waiting for the relay. translate the handle of the switch S1 is in a different position, and then return back. The capacitor C2 is discharged through resistor R5 and after returning the switch to its original position will begin charging again. Periodically rearranging the selector knob, according to the watchdog relay to keep the load turned on.
If you want to disable the watchdog relay, it is sufficient to set the selector knob to right in the diagram position. Then power on the relay is not supplied, and the load will remain included in the network via the relay contacts.
The first unit conveniently be made of a fork-"tee", which you often use to enable several users to one outlet. She removed the two sockets, and replaced the fuse.
The second block can be mounted in any enclosure of suitable dimensions.
Capacitor C1 is an electrolytic of any type. Capacitor C2 must be paper. If its capacity is less than indicated in the diagram, it is necessary to proportionally increase the resistance of the resistor R3 (it can be made up of series-connected resistors as possible resistance).
Relay K1 - RCM-1, passport RS4.500.892. The resistance of its windings 3300 Ohms, the operating current does not exceed the 7.2 mA. Two switching group of the relay are connected in parallel to increase reliability.
If operation of the device at the moment of ignition of the thyratron relay is energized and immediately let go, increase the capacitance of the capacitor C1. You may then have to pick up the resistors R1 and R2.
When establishing the device you should be careful (its elements are under voltage!), all soldering to make when "tee" off of the wall outlet.
Author: A. Aristov, Pervouralsk, Sverdlovsk region; Publication: N. Bolshakov, rf.atnn.ru