Elektor Team
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A seven-segment display made from LED filaments

Based on a Labs project | January 2015 | Find it here
Conventional low-energy lamps are a dying breed as we have entered the LED era. LEDitron is a seven-segment display module made from LED filaments, similar to a vintage Numitron tube but with better energy efficiency.Low-energy lamps first appeared in the 1980s — actually not all that long ago. Unfortunately, the first compact fluorescent lamps (CFLs) were not particularly compact and looked more like a jam jar with a screw base. Fortunately, they became smaller in the course of time.
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35 to 100 V adjustable output voltage range
100 mA maximum output current
12 V / 1 A supply voltage
Suitable for four to six LED filaments, depending on the brightness setting
Fully designed with through-hole components
Component list
Component List
Power Supply Board
R1 = 10Ohm
R2–R8 = 1kOhm
R9, R10 = 2.2kOhm
R11 = 3.3kOhm
R12–R20 = 4.7kOhm
R21,R22 = 27kOhm
R23–R37 = 100kOhm (R36,R37 optional)
R38 = 390kOhm
P1 = 5kOhm trimpot
C1 = 330pF
C2 = 100nF
C3 = 4.7µF 100 V, low ESR
C4,C5 = 470µF 25V, low ESR
L1 = 47µH, Würth WE-PD3 744 591 47
D1 = MUR160G
T1 = B547B
T2 = BC639
T3 = BC640
T4 = IPP200N15N3 G
T5–T13 = MPSA42
T14,T15 = MPSA92
IC1 = ICM7555
F1 = 1.85A, 30V MCC33161
K1 = 2-pin PCB screw terminal block, 5mm pitch
K2 = 10-pin (2x5) boxheader, 0.1’’ pitch
K3 = 9-pin pinheader
PCB # 150448-3 from Elektor Store
Component List
7-segment display
R1 = 220Ohm
LED1 = 5mm diam.
K1 = 10-way pinheader receptacle, 0.1’’ pitch
PCB # 150448-1 from Elektor Store
Component List
Stacking Board
K1,K2 = 10-pin pinheader, 0.1’’ pitch
K3 = 9-way pinheader receptacle, 0.1’’ pitch
K4 = 3-pin pinheader, 0.1’’ pitch
PCB # 150448-2 from Elektor Store
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