Wednesday, December 25, 2013

FM Radio Station Power Monitor Part 13

Radio switch schematic

Follow the schematic diagram to wire in a power switch and a red LED power-on monitor light.

The switch turns the radio radio station transmitter on and off. When on, the red LED will remain lit. The LED monitor light does not interfere with the radio station transmitter. This is the first modification add-on to the radio station.

Parts required, 1 LED, 1 resistor, 1 SPST or SPDT (for a future add on) toggle switch. Use the LED wiring guide pictorial and schematic to determine proper LED polarity.

Testing the LED power on/off indicator circuit. The resistor value of 820 ohms was determined with the use of a resistor ohm substitution box.
The guide shows a "looking down view" from above the LED. Shown in the schematic is a SPST switch. The actual radio transmitter will have a SPDT switch.

The 3mm red LED costs NT$1 each (US$.033 each) in a package of 100. The SPDT toggle switch SW1 is priced at NT$18 (US$.60). The resistor R1 is 820 ohm or the next larger resistance.

FM Radio Station Part 5 Index