Irregular Flasher
Ludwig Libertin C1 R3
4k7
C2
330n 3 D1 4 100n
Two multivibrators with different frequen- IC1.A IC1.B
& &
cies can be built using the NAND gates
of a 4011 IC. If the output of IC1.B is pos- R2 1 2 6 5 R5
itive with respect to IC1.C, LED D1 is on. 1M 1M
R1 R4
As the levels of IC1.A and IC1.D are
exactly opposite, D2 is always on when
10k
10k
D1 is off, and the other way around. R6
The two oscillators have different frequen- 4k7
cies, which are determined by the values 10 D2 11
of R2/C2 and R5/C5 respectively IC1.C
& +5V...+15V &
IC1.D
according to the formula
8 9 13 12
f0 = 1 ÷ (1.4 RC)
With the given component values, the fre- 14
quencies are 2.2 Hz and 7.2 Hz. Low- IC1 IC1 = 4011
7
current LEDs should be used, since the
CMOS IC cannot sink or source sufficient 020221 - 11
current for ‘normal’ LEDs. The values of
series resistors R3 and R6 are suitable for 4011 can be operated over a supply volt- dentally, the part number of the quad
a supply voltage of 12 V, in which case age range of 5–15 V. Higher currents can gate IC in the HC family is HC7400.
the current consumption of the circuit is be provided by the HC family (supply volt- (020221-1)
around 5 mA. However, in principle the age 3–6 V) or the HCT family (5 V). Inci-
2 elektor electronics - 7-8/2004
