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This charming little circuit is a genuine four-digit running-text display, complete with a Christmas / New Year’s greeting. Naturally, any competent programmer can easily arrange to have a different text scroll across the display. The associated soft-ware, including the source code, can be downloaded from the Free Downloads section of our website or obtained from Readers Services on diskette (order number 020365-11).   As can be seen from the schematic, the hardware consists of little more than an AT90S1200 microcontroller, a 4-digit LED display and a 5-V voltage regulator. The only external circuitry needed by the microcontroller consists of a reset circuit and a 4-MHz crystal, and the remainder of the components are limited to a few decoupling capacitors. Circuit diagram : Simple Mini Running Text Display Circuit Diagram In the prototype model, an Osram SLO2016 display module was used. Although this four-digit module measures only 10×20 mm, it provides an especially clear and ...

Radio Band Position Display Circuit diagram. 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). Radio Band Position Display 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 selecte...

Circuit Diagram Description The circuit was designed to create a low cost frequency meter that will cover the range of 1 Hz to 1 MHz with a digital indication using three 7-segment displays. Terminology 7805 – a 3-terminal 1A positive voltage regulator with output transistor safe area compensation, internal short circuit current limiter, output voltage of 5V, 12V, and 15V, internal thermal overload protection, no external components, and current output in excess of 0.5A 4026 – a decade counter where the count advances as the clock input becomes high and has a maximum current of about 1 mA with a 4.5 V supply and 4 mA with a 9 V supply, which can light the appropriate segments of a common cathode 7-segment display 4583 – a 4-bit single-chip microcomputer designed with CMOS technology using a simple, high-speed instruction set, equipped with four 8-bit timers, a 10-bit A/D converter, interrupts, oscillation circuit switch function, and used in application with remote control transmitt...