Article
Magnetic Flux Density Meter
with a simple pick-up coil
How do you know accurately if a magnet is stronger or weaker than one you’ve dubbed your reference device? This simple to build instrument has the answer.
Materials
Gerber file
CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD 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.
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PCB
Component list
Resistors:
R1 = * Ohm (100 suggested starting value only)
R2,R5 = 2k7 SMD case size 0805
R3,R4 = 2,2 SMD case size 0805 (e.g., Farnell # 310-4515)
R6,R9,R10,R11 = 10 k, SMD, case size 0805
R7,R8 = 100k SMD, case size 0805
R12 = 1k, SMD case size 0805
R13 = 22
R14 = 39k
P1 = 10 preset, Bourns type 3329H (e.g., Farnell # 345-970)
P2 = 10k preset H
Capacitors:
C1,C2 = 2µF2 25V radial
C3,C7 = 100nF, SMD, case size 0805
C4,C5 = 22pF, SMD, case size 0805
C6 = 10µF, 63V, radial
Semiconductors:
D1 = high current Schottky diode, case size SOD-323, e.g., Zetex type ZHCS400 (Farnell # 301-4850)
IC1 = LP2950CZ-5.0
IC2 = MAX4130EUK-T (Maxim) case size 5-lead SOT-23, or MAX4122EUK-T (Farnell # 353-4169)
IC3 = PIC16F876-20/SP, programmed, order code 040258-41 (28-pin narrow DIP case)
Miscellaneous:
K1 = 2-way pinheader
S1 = on/off switch, 1 make contact, chassis mount
S2 = 2-pole, 2-way changeover switch, chassis mount (+ 6-way SIL header if necessary)
S3 = pushbutton, 1 make contact
X1 = 16MHz quartz crystal, HC-49/4H case
LCD1 = LCD, 1 line, 16 characters, with 14-way pinheader
BT1 = battery pack, 4 x 1.5V AA size
Enclosure with battery compartment for 4 AA batteries, e.g. OKW shell-type case V155 (SG155), version III (OKW # A9408338), size approx. 158x95x33 mm
PCB, ref. 040258-1, from ThePCBShop
R1 = * Ohm (100 suggested starting value only)
R2,R5 = 2k7 SMD case size 0805
R3,R4 = 2,2 SMD case size 0805 (e.g., Farnell # 310-4515)
R6,R9,R10,R11 = 10 k, SMD, case size 0805
R7,R8 = 100k SMD, case size 0805
R12 = 1k, SMD case size 0805
R13 = 22
R14 = 39k
P1 = 10 preset, Bourns type 3329H (e.g., Farnell # 345-970)
P2 = 10k preset H
Capacitors:
C1,C2 = 2µF2 25V radial
C3,C7 = 100nF, SMD, case size 0805
C4,C5 = 22pF, SMD, case size 0805
C6 = 10µF, 63V, radial
Semiconductors:
D1 = high current Schottky diode, case size SOD-323, e.g., Zetex type ZHCS400 (Farnell # 301-4850)
IC1 = LP2950CZ-5.0
IC2 = MAX4130EUK-T (Maxim) case size 5-lead SOT-23, or MAX4122EUK-T (Farnell # 353-4169)
IC3 = PIC16F876-20/SP, programmed, order code 040258-41 (28-pin narrow DIP case)
Miscellaneous:
K1 = 2-way pinheader
S1 = on/off switch, 1 make contact, chassis mount
S2 = 2-pole, 2-way changeover switch, chassis mount (+ 6-way SIL header if necessary)
S3 = pushbutton, 1 make contact
X1 = 16MHz quartz crystal, HC-49/4H case
LCD1 = LCD, 1 line, 16 characters, with 14-way pinheader
BT1 = battery pack, 4 x 1.5V AA size
Enclosure with battery compartment for 4 AA batteries, e.g. OKW shell-type case V155 (SG155), version III (OKW # A9408338), size approx. 158x95x33 mm
PCB, ref. 040258-1, from ThePCBShop
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