Category Archives: Projects

7447 BCD to 7 segment display driver

7447 Binary coded decimal to 7 segment display driver

7447 Binary Coded Decimal counter


the 7447 decodes BCD 0-15 to there decimal equivalents plus 6 distinct character’s for letters A-F. the font is set to have tailless 6 and 9 characters. If required look at the 7448 the nice feature of this IC is that it has a “following display blanking” pin (Pin4) and will display 0 if it is the highest active unit but will display ” ” nothing if not needed, so in a 4 digit system you will have as an example ” 52″ and not “0052”

Tie Vcc (pin 16) to +5v and GRD (pin 8) to 0V also to get this operating as a single display tie all /(LT) /(RBI) and /(BI RBO) high.


7447 Font table

7447 font display output


74HC4040 Counter

74HC4040 Counter

12-Bit binary counter

This circuit is the basic setup of a 74HC4040 binary counter it is driving 12 LED’s. to build this first connect Vcc (pin 16) to the +5v rail and Grd (pin 8) to the 0v rail of your project board. You will also need a square clock pulse that is supplied by a 555 circuit you can find this on my other page here. this is a 12-bit counter and will count up to 4095 before returning to 0 if connected to the 1Hz clock pulse that will take just over 1 hour to overclock. To reset this to 0 you can press the switch on pin 11(Master Reset) and this will force all the outputs to 0 instantly.


555 Timer

555 Timer

astable 555 circuit

This is a 555 IC in the Astable configuration it will give off a square-wave form with a frequency f) The capacitor (C) is charged through resistor (R1+R2) and discharges through R2 only.

( C is in Farads & R are in ohms )





Try this:

To build a astable 555 with +/- 1Hz period and 50% Duty cycle you will need:

555 IC,  R1-10k,  R2-150k,  C-4.7uF,  C1-10nF (103)

All this can be bought at Maplin Electronics