Automatic backup power supply of the radio station
There are situations, when we need to secure, so that the radio station can work even in the event of a power failure. UPS backup power supplies are available on the market, which work as automatically switched converters 12V DC to 230V AC.
Radios are usually powered by low DC voltage. Advantageously, we can use gel lead-acid batteries as a backup source. But how to achieve, so that the battery is always charged, when we need it and substitute energy from the source in the event of a power outage? The solution is very simple and cheap.
The solution of the automatic backup power supply of the radio station is clear from the diagram. Shows the situation in case of power failure: The TCVR is powered via a relay contact from the battery. In the presence of voltage from the source, the relay closes and the TCVR is powered from the source. At the same time, the battery is charged via a diode and a limiting resistor. The diode prevents the battery from discharging through the source and closing the relay with battery voltage.
We determine the value of the limiting resistor according to the battery capacity, so that it is recharged. With the considered source of voltage 13.8V and voltage drop 0.8V on the diode, a resistance arises 4,7 to 33 ohms. It is advisable to connect an ammeter to the branch during resuscitation and select such a resistor, to charge the battery with low current.
