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Versatile DC Power Meter

Voltage, current, and even more

Versatile DC Power Meter
Every power supply worthy of the name should display the voltage and current. This compact DC power supply instrument module can be used with new supplies and older types lacking this capability. And thanks to microcontroller technology, it offers some bonus features.
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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.

Resistors
R1 = 27k?
R2,R3 = 27k?, 1%
R4 = 10k?, 1%
R5 = 10?

R6,R8 = 1k?
R7 = 100?  0.1%
R9 = 10k?
R10 = 10k? 0.1%
P1 = 10k? preset
P2 = 100k? cermet preset
Precision shunt 1 m( 50 A, 0.5%* or 10 m(/5 A, 0.5%*, Isabellenhütte type PBV R001 or R01 (Conrad Electronics # 447315 or  # 447323)
Capacitors
(all 2.5mm lead pitch)
C1,C3-C7,C9,C12 = 100nF
C2 = 100µF 16V
C8 = 10nF
C10,C11 = 22pF ceramic
Semiconductors
D1 = 1N4004
D2,D3 = zener diode 7V2, 500 mW
T1= BS250*
IC1 = 7805 (TO220)
IC2 = LM335 (TO92)
IC3 = ATMega8PC, programmed for 4x20-LCD, order code 070559-41
IC4 = TL081P (DIL)
Inductor
L1 = 10µH
Miscellaneous
X1 = 8MHz quartz crystal
One 8-way turned-pin IC socket
One 28-way turned-pin IC socket
LCD 2x16 or 4x20, DIP, with backlight, Electronic Assembly (Conrad Electronics # 181755 resp. # 181863)
JP1 = (temporary) pushbutton
JP2,JP3 = jumper or wire link
JP4 = jumper or switch, 1 make contact*
U-profile heatsink, 12 K/W for TO220 (IC1)
4 M3i/M3a spacers, length 18mm
Two 10-way socket strip, lead pitch 2.0mm (remove 1 pin)
PCB, order code 070559-1
Project software and PCB layout freely downloadable from www.elektor.com
*see text

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