Ton  Giesberts
About the article

VariLab 402 (2/3)

VariLab 402 (2/3)
The control portion of the VariLab power supply uses a microcontroller to set the desired output voltage and current and to measure all significant voltages and currents in the circuit. All measurements and settings are shown on a four-line LCD module. Naturally, there is also a USB port for communication with a PC.
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Component List
Resistors
Default 0.125W, SMD 0805)
R1–R4,R8,R14,R16,R22–R25 = 1k? 1%
R5 = 2.87k? 1%, 0.1W
R6 = 1.80k? 1%
R7 = 10M? 1%
R9 = 10k? 5%
R10 = 820? 1%
R11 = 8.87k? 1%
R12 = 1.21k? 1%
R13 = 1.30k? 1%
R15 = 15? 1%, 0.25W
R17 = 10? 5%
R18,R20 = 2.2k? 5%
R19 = 47? 5%
R21 = not fitted
R26 = 33k? 5%
R27 = 56k? 5%
P1 = 500? 10%, 0.5W, 25-turn preset, top adjustment (Bourns 3296Y-1-501LF)
P2 = 10k? 20%, 0.15W, preset, top adjustment

Capacitors
C1,C2 = 22pF 50V, 5%, SMD 0805 C0G/NP0
C3..C9,C13 = 100nF 25V, 10%, SMD 0805 X7R
C10 = 10µF 63V, 20%, diam. 6.3mm, 0.1” pitch
C11 = 100µF 25V, 20%, diam. 6.3mm, 0.1” pitch
C12 = 4.7µF 6.3V, 10%, SMD 0805 tantalum (case R, AVX TAJR475K006RNJ)

Inductors
L1,L2 = 330? @ 100MHz, 0.08? 1.7A, SMD 0603

Semiconductors
D1 = LED, red, 3mm, wired
D2,D3,D4,D5 = BAS70-04 (SMD SOT-23)
D6 = PRTR5V0U2X (SMD SOT-143B)
D7,D8 = TS4148 RY (SMD 0805)
T1,T2 = BC817-25 (SMD SOT-23)
IC1 = ATxmega128A4U-AU (SMD TQFP-44), programmed, Elektor Store #120437-41)
IC2 = MCP6004 (SMD SOIC14)
IC3 = KF33BDT-TR (DPAK-3)
IC4 = 4N25 (DIP-6)
IC5 = LM35 (TO-92)
IC6 = LM336Z-2V5 (TO-92)

Miscellaneous
K1 = USB connector, type B, PCB mount, wired, vertical model (Lumberg 2411 01)
K2 = 6-pin (2x3) pinheader, 0.1” pitch
K3 = 14-pin (2x7) pinheader, 0.1” pitch
K4 = 2-way screw terminal block, 0.2” pitch
K5,K6,JP4 = 3-pin pinheader, 0.1” pitch
K7 = 4-pin pinheader, 0.1” pitch
JP1,JP2,JP3 = 2-pin pinheader, 0.1” pitch
jumpers for JP1,JP2,JP3,JP4
S1,S2 = 18PPR rotary encoder with integrated pushbutton (e.g. Alps EC11E183440C)
S3 = pushbutton, PCB mount (e.g. Multimec RA3FTL6)
S3 = cap for pushbutton, h=19mm (e.g. Multimec 1S09-19.0)
BZ1 = piezo buzzer, 1.5–16 VDC, max. 8 mA, diam. 14mm, 7.62mm pitch
X1 = 16MHz quartz crystal, CL 18pF, dim. 5 x 3.2mm (Abracon ABM3-16.000MHZ-B2-T)
LCD1 = 4x20 characters, with backlight, Elektor Store #120061-73
PCB # 120437-2

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