This circuit will divide the frequency of a TTL compatible square wave signal by a factor from 0 to 999. The circuit comprises three decade counters IC1 to IC3 and a few NAND gates. The three 7490?s are cascaded and count is the input signal. When the desired and count reached all the inputs of IC4 become high, so the output goes low. This triggers the monostable consisting of IC5B and IC5C, which provides a sort output pulse. The output of IC5A goes high, resetting the three counters and the count then begins again. To program the counter it is first necessary to work out the binary coded decimal (BCD) equivalent of the required division ratio.

The clock circuit above uses seven ICs and 19 LEDs to indicate binary coded decimal time. The LEDs can be arranged (as shown in example above) so that each horizontal group of 3 or 4 LEDs represents a decimal digit between 0 and 9 and each individual LED represents a single bit or (binary digit) of the value. Binary digits have only two values (0 and 1) so a number written in binary would be something like 1001 or 0011, which represents decimal numbers 9 and 3 respectively. From right to left, each binary (1) represents increasing powers of 2, so that a 1 in the right hand place represents 2^0=1 and the next place to the left is 2^1=2 and then 2^2=4, and so forth.

A 555 timer operating in the astable mode generates the driving pulses and two 4518 dual BCD (binary coded decimal) counters provide the square waves. A TL081 op amp serves as an output buffer-amplifier, and potentiometers Rl and R2 are used in order to control the pulse`s frequency and amplitude, respectively. The output-frequency range can be varied by changing Cx. For example, a value of 0.1 gives a range from about 0.1 to 30 Hz, and a value of 470 pF gives a range from about 10 Hz to 1.5 kHz.

Binary Coded Decimal is a number system that only counts from 0 to 9 and then repeats. The table below shows the conversion between the different numbering systems and BCD code. BCD is also called 8421 because the binary LSB counts as a 1, the next bit adds 2, than 4 and the final MSB bit adds 8 to the final numbers. So a BCD 1001 is equal

This circuit is composed of a temperature sensor, amplifier, V/F converter, three digit binary coded decimal (BCD) counter, time base and seven segment led displays. In addition to the 9400 V/F converter, other ICs need for this project include the LM334 temperature sensor, LF353 dual op amp, NE555 timers, 74LS00 NAND gate, MC 14553 three digit

All of ACC`s repeater and remote base products support control of synthesized remote base transceivers. One form of frequency control supported is compatible with transceivers using thumbwheel frequency selection. The controllers supply BCD (binary coded decimal) formatted data in a serial bit stream, which may be captured by external shift regist

When a keypad switch is pressed - this circuit will reproduce its value in Binary Coded Decimal from. I`ve used a 12-key pad. But it may be expanded to 16 keys - to provide Hexadecimal to BCD conversion. The circuit is constructed in two parts. There`s a keypad module - and a memory module. On its own - the keypad module only produces a transient