Automatic TV turn on. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Телевидение
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When a home VCR is used with a television that does not have a remote control system, a simple device can be used to automatically turn on the TV when the VCR is turned on. No modification to the TV or VCR is required.
The operation of the device (see figure) is based on the change in the current consumed by the VCR during the transition from standby to working mode.
Power is supplied to the TV through a current switch consisting of a rectifier bridge VD1, in the diagonal of which the thyristor of the optocoupler DA1 is included. The optocoupler LED is connected to the power supply circuit of the VCR through the VD2 bridge. Capacitor C1 and resistor R1 filter the rectified voltage. Resistor R2 is selected in such a way that when the VCR is off, the current through the optocoupler LED is less than the unlocking one, and when the VCR is on, it exceeds it.
It is convenient to mount the device in the mains plug housing, which is connected by a three-wire cable to a double socket, which includes a TV and a VCR. Adjustment of the device is reduced to the selection of the resistor R2. It is necessary to achieve a clear operation of the thyristor when turning the VCR on and off.
At the time of adjustment, instead of a TV, you should connect an incandescent lamp.
If the power consumed by the TV exceeds 200 W (for example, if you have a tube color TV), then the VD1 bridge must be replaced with a more powerful one. You can also use a powerful optosimistor, in which case the VD1 bridge is not required.
It is undesirable to use two back-to-back optothyristors in this device due to the spread in the operating current.
Author: A.N. Spiridonov, Kyiv
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