วงจรตั้งเวลา 20 วินาทีครับ ใช้ IC 555
Parts:
C1__________10uf 16V Electrolytic Capacitor
C2__________0.01uf Ceramic Disc Capacitor
R1__________1 Meg Pot
R2__________10 K 1/4 Watt Resistor
D1,D2_______1N914 Diodes
U1__________555 Timer IC
RELAY______9V Relay
S1__________Normally Open Push Button Switch
MISC_______Board, Wire, Socket For U1
Notes:
1. R1 adjusts the on time.
2. You can use a different capacitor for C1 to change the maximum on time.
3. S1 is used to activate the timing cycle. S1 can be replaced by a NPN transistor so that the circuit may be triggered by a computer, other circuit, etc.
