A simple astable
multivibrator(
alternately blinking
LEDs)
5V
______________________________
| | | |
LED1 V | | V LED2
- | | -
| | | |
| | | |
| |R1 | |R2 | |R3 | |R4
| | | | | | | |
| | | |
*-----+---. .-----+-----*
\ | `-+-. | /
T1 \| | + | |+ | |/ T2
|--*-||--' `||-*--|
|/| C1 C2 |\|
/ \
| |
-----*-----------------------'
GND
legend:
- : wire
+ : crossed wires (not connected)
* : connection
Parts:
T1, T2 : NPN Transistor
LED1, LED2: normal LED
R1, R4 : resistor 330 ohms
R2, R3 : resistor 10K
C1, C2 : electrolytic capacitor 47uF
The T1 and T2 can be just about any NPN-
transistor(for example
the BC546B). The
frequency of the
flashing can be
changed by using
different capacitors(the lower the
capacitance
the
faster the
LEDs will
flash ) or by changing R2 and R3
. The
frequency is
dependant
on how fast the
capasitors are
charged; a high
capacitance
recharges slower, a low faster.
R1 and R2 limits the
current through
LED1 and
LED2 and
should not be
switched with
resistor lower than 250 ohm.
Also if these gets to high the
LEDs won't light up.