Article
Universal Mains Filter
There are plenty of mains filters available, with or without sockets, with or without a switch, etc. In any case, this filter is very versatile as far as the maximum working current is concerned. It so happens that the footprint of the coil remains the same for different currents. Depending on the required specification, you can use a specific coil (which the manufacturer calls a ‘Current-Compensated Ring Core Double Choke’). The table below lists a suitable range of coils made by Epcos. When we designed the PCB we chose the smallest size that still gave a wide selection of maximum currents.
Materials
Gerber file
CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.
Elektor recommends the Elektor PCB Service service from its business partner Eurocircuits or AISLER as the best services for its own prototypes and volume production.
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PCB
Component list
Resistors:
R1,R2 = 470kOhm
Capacitors:
C1,C2 = 10nF 275 VAC X2, lead pitch 10 or 15mm
C3,C4 = 100 n/275 VAC X2, lead pitch 15mm
Inductors:
L1 = B82721-A2401-N20, Epcos (Farnell 976-477)
Miscellaneous:
K1 = 3-way PCB terminal block, lead pitch 7.5mm
K2 = 2-way PCB terminal block, lead pitch 7.5mm
R1,R2 = 470kOhm
Capacitors:
C1,C2 = 10nF 275 VAC X2, lead pitch 10 or 15mm
C3,C4 = 100 n/275 VAC X2, lead pitch 15mm
Inductors:
L1 = B82721-A2401-N20, Epcos (Farnell 976-477)
Miscellaneous:
K1 = 3-way PCB terminal block, lead pitch 7.5mm
K2 = 2-way PCB terminal block, lead pitch 7.5mm
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