TREE

This circuit is an add-on unit for radio receivers that lack band-position display. The circuit presented here can show up to nine bands. It also incorporates a novel feature to make the display dance (blink) with the audio level from the receiver. The power-supply for the circuit can also be derived from the radio-set. The conversion of selected channel to BCD format is achieved using diodes D1 through D15 in con-junction with resistors R4 to R7. The voltages developed across these resistors (R4 through R7) serve as logic in-puts to BCD inputs of BCD to 7-segment de-coder IC1 (CD4511). Circuit diagram : Radio Band Position Display Circuit Diagram When all switches are in  ‘off’ state, the volt-age across resistors R4 through R7 is logic zero, but when any of the switches S1 through S9 is slided to  ‘on’ position, the output across these resistors changes to output proper BCD code to represent the selected channel. This BCD code is converted to 7-segment display by IC1. By this arr...

The following display features eight 7-segment displays arranged in two rows of four digits. The on-board MAX7219 driver enables you to easily add eight 7-segment LED displays to your project using only 3 I/O pins of microcontroller. The major advantage of using this board is the time-division multiplexing operations required for continuous refreshing of the display digits are performed by the MAX7219 chip, thereby keeping the microcontroller free for doing other pressing tasks. It is suitable for displaying two variable values simultaneously in a project, such as displaying temperature and humidity, or current and voltage, etc. [ ]