A Current Source for Testing (Z-)Diodes

Checking Z-Diodes from 1 to 54 V @ 1 to 50 mA

This circuit is essentially a constant-current source that can be switched in steps from 1 to 50 mA. It can be used to test Z-diodes up to a maximum of 54 V. Thanks to a 60-V step-up converter, the device can be powered by the usual 5 to 12 V.

EUR

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Materials

Philippe Le Guen, Zener Diode Tester, Elektor Labs

MC34063 datasheet, Texas Instruments

Ton Giesberts, Zener Diode Tester, Elektor Labs

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Bill of Materials

Component List

Resistors
R1 = 3.3 kΩ, 600 mW, 1%
R2 = 0.15 Ω, 1 W, 5%, LS 12.7 mm, ø 3.5 mm
R3, R8 = 180 Ω, 600 mW, 1%
R4, R6, R16 = 1 kΩ, 600 mW, 1%
R5, R19 = 47 kΩ, 600 mW, 1%
R7 = 3.9 kΩ, 1 W, 5%, LS 12.7 mm, ø 3.5 mm
R9, R10, R12 = 10 kΩ, 600 mW, 1%
R11, R13 = 100 Ω, 600 mW 1%
R14 = 249 Ω, 600 mW, 1% *
R15 = 499 Ω, 600 mW, 1% *
R17 = 2.49 kΩ, 250 mW, 1% *
R18 = 4.99 kΩ, 250 mW, 1% *

Capacitors
C1 = 470 uF / 35 V, 20 %, Ir = 1.86 A, ø 12.5 mm, LS 5 mm, ESR = 0.038 Ω (Panasonic EEUTP1V471)
C2 = 1 uF / 100 V, 10 %, X7R, LS 5 mm
C3 = 2.2 nF / 50 V, 10 %, X7R, LS 5 mm
C4, C7 = 100 nF / 100 V, 10 %, X7R, LS 5 mm
C5 = 100 uF / 100 V, 20 %, ø 14 mm max., LS 5 mm
C6 = 1 nF / 100 V, 10 %, X7R, LS 5 mm

Inductor
L1 = 100 uH, Irms = 2.4 A, Isat = 3.5 A, 0.09 Ω, radial, pitch 2.5/5/10 mm, ø 14 mm max. (Kemet SBC8-101-242)

Semiconductors
D1 = MUR120G, DO-41
D2, D4 = STPS3150RL, DO-201AD
D3 = Z-diode, 18 V, 1.3 W (BZX85C18)
D5 = Z-diode, 5.1 V, 0.5 W (1N5231B)
LED1 = LED in pushbutton S1
LED2 = LED, green, 3 mm
IC1 = MC34063, DIP-8
IC2 = LM4040BIZ-5.0/NOPB, TO-92 (TO-226AA-3)
IC3 = TL051CP, DIP-8
T1 = BC327.25, TO-92
T2 = STP40NF10L, TO-220
T3 = IRF9510PBF, TO-220
T4 = 2N7000, TO-92

Others
K1, K2, S1, S3 = 2way screw terminal block, LS 3.5 mm, max. 1.5 mm²
connected to K1 = USB-C socket, 30 V / 3 A, chassis mounted, wired, 9 x 16 mm
connected to K2 = Banana Connector, 2 mm, Socket, 60 VDC, Panel Mount, red (Multicomp 24.102.1)
connected to K2 = Banana Connector, 2 mm, Socket, 60 VDC, Panel Mount, black (Multicomp 24.102.2)
Test clip, red, 30 VAC / 60 VDC (Hirschmann 931467101)
Test clip, black, 30 VAC / 60 VDC (Hirschmann 931467100)
S1 = Pushbutton, panel mount, SPST-NO, 30 DC / 100 mA, with red LED *
S2 = Rotary Switch, 6 position, 2 pole, 30°, 250 V / 150 mA
S3 = Toggle switch, panel mount, SPDT, solder lugs, 28 VDC
T2, T3 = Heat sink, 15°C/W, FK 214 SA-CB
Enclosure Hammond 1591XXSSBK, ABS, 110 x 82x44 mm
Knob for S2, round shaft 6 mm, ø 21 mm, with indicator line (Multicomp CP-LB21-6-6D)
4 x Self-tapping screw #4-1/4", carbon steel, pan head
Banana plug, red, 2 mm, 60 VDC (Multicomp 25.205.1)
Banana plug, black, 2 mm, 60 VDC (Multicomp 25.205.2)
Banana socket, black 4 mm, panel mount
Banana socket, red 4 mm, panel mount
for LED1, LED2 = Pin header, 1 x 2, vertical, pitch 2.54 mm
for LED1, LED2 = Pin socket, 1 x 2, vertical, pitch 2.54 mm
for T2, T3 = M3 screw, 10 mm, steel, pan head
2 x M3 washer, plain, steel
4 x M3 nut
for IC1, IC3 = DIP-8 socket