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Dual Voltage/Current Display

For a symmetrical Unilab power supply

Dual Voltage/Current Display
For the Unilab power supply module, we have developed a special meter circuit in the Elektor Labs with a four-line display that shows the output voltages and currents of a symmetrical configuration with two Unilab circuit boards.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor 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 its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Extra info, Update


* Readings shown on a large backlit LCD module with 4 lines of 20 characters
* Voltage and current of each supply output (positive and negative) displayed
* Internal temperature of PS enclosure also displayed
* Selectable °C or °F temperature indication
* Signal conditioning circuitry specifically designed for a dual Unilab power supply
* Software-aided calibration procedure
* Powered by a separate transformer (2 ( 8 V / 3.3 VA)

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The BOM (Bill of Materials) is the technically exhaustive listing of parts and other hardware items used to produce the working and tested prototype of any Elektor Labs project. The BOM file contains deeper information than the Component List published for the same project in Elektor Magazine. If required the BOM gets updated directly by our lab engineers. As a reader, you can download the list here.
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(0.25 W unless indicated otherwise)
R1 = 499Ohm 1% 0.6W
R2 = 1.00kOhm 1% 0.6W
R3,R15,R21,R22,R23 = 10kOhm 5%
R4,R6 = 100kOhm 5%
R5,R16 = 68kOhm 5%
R7 = 3.3kOhm, 5%
R8 = 47kOhm 5%
R9 = 12kOhm 5%
R10 = 45.3kOhm 1% 0.6W
R11,R12 = 24.0kOhm 1% 0.5W
R13,R14 = 6.81kOhm 1% 0.6W
R17,R18,R19,R20 = 100Ohm 5%
R24 = 4.7Ohm 5%
R25 = 470Ohm 5%
R26 = 15Ohm 5 %
P1 = 200Ohm trimpot, e.g. Vishay Spectrol type M64W201KB40
P2 = 5kOhm trimpot, e.g. Vishay Spectrol type M64W502KB40
P3 = 500Ohm trimpot, e.g. Vishay Spectrol type M64W501KB40
P4 = 10kOhm trimpot, e.g. Piher type PT10LV10-103A2020
C1,C4,C5,C6,C8,C9,C10,C13,C14 = 100nF ceramic, lead pitch 5mm
C2,C3 = 15pF 2%, ceramic, lead pitch 5mm
C7 = 100µF 25V, radial, lead pitch 2.5mm
C11,C12 = 10µF 63V, radial, lead pitch 2.5mm
C15,C16 = 220µF 25V, radial, lead pitch 3.5 mm
C17,C18,C19,C20 = 47nF, ceramic, lead pitch 5mm
L1 = 10µH 10%, axial, Rs = 0.29Ohm, e.g. Epcos type B78108S1103K
D1,D2,D3,D4,D5 = BAT85
T1 = BC639
IC1 = LMC6464BIN
IC2 = LM35CZ
IC3 = ATmega168-20PU, programmed, contained in kit # 100166-71
IC4 = 7805
IC5 = 79L05
B1 = 80V, 1.5A bridge rectifier (pinout ~ + ~ –), e.g. Semikron SKBB80C1500L5B
K1,K2,K3 = 6-pin (2x3) pinheader, lead pitch 0.1 in. (2.54mm)
K4 = 6-pin pinheader, lead pitch 0.1 in. (2.54mm)
K5,K6 = 2-way PCB terminal block, lead pitch 5mm
J1,S1 = 2-pin pinheader, lead pitch 0.1 in. (2.54mm)
LCD1 = 16-pin pinheader, lead pitch 0.1 in. (2.54mm)
LCD1 = 16-pin SIL connector for display, lead pitch 0.1 in. (2.54mm)
X1 = 10MHz quartz crystal, HC-49/S, 50ppm, CL = 12pF
LCD, 4x20 characters with background lighting, dim. 60 x 98 mm, e.g. HTDISPLAY HC200401C-YF62L-VA
PCB # 100166-1
Software en PCB design files: free download
Kit of parts incl. PCB, programmed controller and LCD: Elektor order # 100166-71

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