Parts List:U1 = LM555 timer/oscillatorU2 = 74LS190U3 = 74LS42U4 = 74LS76P1 = 10K, potentiometerR1 = 10KR2-R11 = 220 ohmC1 = 100nF, ceramic10 LED’s, ultra-bright
U1, the 555 timer/oscillator clocks a 74LS190 up/down counter (U2).The 74LS190 drives a BCD decoder driver 74LS42 (U3). The 74LS76 has as task to reverse the count on 0 to 9 to 0 and so on.P1 sets the up/down counter speed.R2 to R11 are all 220 ohm carbon-type resistors.
You may have noticed in the diagram it does not specify the ’LS’ (Low Schottky) IC types but done for simplicity reasons.If your circuit is powered from a battery you definately should use the LS versions as the current draw is significantly less and so your battery pack will last longer.Same for the 555; use the cmos version to cut down on power.
Click here LM555 for more information and data on the 555 timer/oscillator IC. Keep wires as short as possible since too long wires may be a cause for interference (RFI).