• on Test & Measurement
  • Published in issue 4/2014 on page 42
About the article

Precision Adjustable DC Current Source

With integrated hi-Z voltmeter

Precision Adjustable DC Current Source
Parroting the Science Class teacher an adjustable current source consist of any old voltage source, a variable resistor and applying Ohm’s law, right? In Elektor Class, the project described here is the next dimension after I equals V-over-R, offering precision and versatility rivaled only by $$$ gear found in professional labs. How about a lowest range of 10 nanoamps?
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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.

Download the BOM list
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.
Want to learn more about our BOM list? Read the BOM list article for extra information.
Component List
R1,R55 = 12kOhm 5% 400mW
R2,R40 = 180kOhm 5% 400mW
R3,R10 = 50MOhm 1% 1W
R4,R15 = 10MOhm 1% 600mW
R5,R6,R7,R11,R12,R13,R16,R21,R22,R57,R58,R66 = 1MOhm 1% 500mW
R17 = 1MOhm 0.1% 250mW
R8,R14,R26,R27,R67 = 100kOhm 1% 500mW
R19 = 100kOhm 0.1% 250mW
R9,R54 = 56.2kOhm 1% 600mW
R18,R53,R56 = 4.64kOhm 0.5% 250mW
R20,R25,R44,R47,R48,R65 = 680kOhm 5% 500mW
R23 = 1.1kOhm 1% 250mW
R24 = 10kOhm 0.1% 250mW
R28,R29,R30,R37 = 10kOhm 1% 500mW
R31,R32,R33,R38 = 1kOhm 1% 500mW
R34,R35,R36,R39 = 100Ohm 1% 400mW
R41,R42,R43 = 220kOhm 5% 500mW
R45 = 0.47Ohm 5% 1W
R46,R49 = 11kOhm 1% 500mW
R50,R51 = 330Ohm 5% 500mW
R52,R60 = 21.5kOhm 1% 600mW
R59,R68 = 3.6kOhm 1% 500mW
R61,R64 = 5.6kOhm 5% 500mW
R62,R63 = 68.1kOhm 1% 600mW
R69 = 0.1Ohm 5% 1W
P1,P3 = 1kOhm multiturn preset
P2 = 50kOhm multiturn preset
P4 = 1MOhm miniature cermet potentiometer
L1 = 680µH 980mA 0.46Ohm
L2 = 100µH 580mA
C1 = 47pF 5%
C2,C14,C17,C19,C20 = 100nF 20%
C3 = 10nF 10%
C4 = 470nF 5%
C5 = 47nF 1% 160V polypropylene
C6,C9 = 100µF 35V radial 20%
C7,C10,C11 = 1µF 63V 10%
C8 = 2.2nF 100V 10%
C12 = 22pF 200V 5%
C13 = 1nF 100V 5%
C15,C16,C18 = 2.2µF 25V radial tantalum
D1,D4 = LT1004CZ-1.2
D2 = 1N5818
D3 = LED, red, low current, 3mm
D5 = 1N4001
T1,T2,T4,T8 = BC557
T3,T6,T7 = BC547
T5,T9 = 2N4392
IC1 = ICL7136
IC2 = CD4070
IC3 = LM3578AM
IC4 = ICL7660
IC5 = LP2951ACM
IC6,IC8 = AD820AN
IC7 = LT1490CN8
S1,S3 = 1x12 rotary switch, Grayhill 56SD30-01-1-AJN (Digikey # 440-7657)
S2 = 3x4 rotary switch, TE Connectivity Alcoswitch (1186546)
S5 = PCB mount slide switch, Knitter Switch MFP201N (134-0113)
LCD1 = LCD module 3.5 digit, transflective, Varitronix VI302-DPRC (Digikey # 1183159)
TP1,TP2,TP3,TP4,TP5,TP6,TP7,TP8,TP9,TP10,TP11,TP12,TP13 = test pin, 1mm diameter, Stelvio Kontek 3110014000540 (Digikey # 305-0913)
K2 = test terminal PTFE, ITT Canon 011-1004-040FB9 (1347796)
Insulated terminal 30A, black (2112490)
Insulated terminal 30A, red (2112491)
Black cap knob, 1/4” shaft (1209791)
Black cap knob, 11.6mm for 1/8" shaft (Digikey # 259-6812)
2x holder for 2 AAA batteries
Enclosure: Teko Coffer A/7, dim. 160x95x45mm
4 x Hexagonal PCB spacers (see text)
PCB # 130287-1 from Elektor Store
(Numbers only in round brackets are Newark/Farnell order codes)

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