Article
Zero-Electrolytics 555 Timer
The more resistance the better
A timer circuit that turns on a pump for a short time every five minutes can be easily made using the famous 555 IC. Unfortunately, it's almost impossible to avoid using electrolytic capacitors to achieve such a long period, which makes the circuit less accurate and reliable, especially in the longer term. However, there is one solution to this problem, and that is to use a special 1 giga-ohm resistor!
Materials
Gerber file
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PCB
Component list
COMPONENT LIST
Resistors
R1 = 1GOhm 0.25W 10%; TE Connectivity type RGP0207CHK1G0
R2,R3 = 10MOhm
R4 = 1kOhm
R5 = 10kOhm
Capacitors
C1 = 390nF, lead pitch 5mm or 7.5mm
C2 = 680nF, lead pitch 5mm or 7.5mm
C3 = 100nF, lead pitch 5mm or 7.5mm
Semiconductors
D1 = 12V 0.5W zenerdiode
D2 = 1N4007
D3,D4 = 1N4148
T1 = IRF1405ZPBF
IC1 = TLC556CN (DIP14)
Miscellaneous
K1–K4 = spade terminals, Faston, 0.2’’ pitch
JP1 = 2-pin pinheader, 0.1’’ pitch
S1 = slide switch, miniature, 1 C/O contact; C&K Components type OS102011MA1QN1
S2 = pushbutton with make contact, 12V 50mA, 6x6 mm
F1 = fuse, 10A fast, 5 x 20 mm, with PCB mount 15A holders; 2 pcs Cooper Bussmann type 1A3399-10-R
PCB # 130257-1
Resistors
R1 = 1GOhm 0.25W 10%; TE Connectivity type RGP0207CHK1G0
R2,R3 = 10MOhm
R4 = 1kOhm
R5 = 10kOhm
Capacitors
C1 = 390nF, lead pitch 5mm or 7.5mm
C2 = 680nF, lead pitch 5mm or 7.5mm
C3 = 100nF, lead pitch 5mm or 7.5mm
Semiconductors
D1 = 12V 0.5W zenerdiode
D2 = 1N4007
D3,D4 = 1N4148
T1 = IRF1405ZPBF
IC1 = TLC556CN (DIP14)
Miscellaneous
K1–K4 = spade terminals, Faston, 0.2’’ pitch
JP1 = 2-pin pinheader, 0.1’’ pitch
S1 = slide switch, miniature, 1 C/O contact; C&K Components type OS102011MA1QN1
S2 = pushbutton with make contact, 12V 50mA, 6x6 mm
F1 = fuse, 10A fast, 5 x 20 mm, with PCB mount 15A holders; 2 pcs Cooper Bussmann type 1A3399-10-R
PCB # 130257-1
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