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Four-channel logic analyser

Digital Inspector

Four-channel logic analyser

The best way to inspect digital signals is with a logic analyser. Sometimes it's useful to be able to do this on-site, or you may have to take a ‘floating’ measurement. The four-channel logic analyser described here is suitable in both situations due to its compactness and because it can be battery powered. The maximum sampling rate is 2 MHz and the circuit has sufficient memory to store 1024 samples of the signal. The dot-matrix display with a resolution of 64 by 128 pixels shows a clear representation of the digital signals.

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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

The circuit diagram erroneously shows X1 as a 20 MHz crystal. This should be 10 MHz as stated in the parts list.

Resistors

R1 = 680Ω

R2,R11-R16 = 10 k

R3-R6 = 330Ω

R7-R10 = 100k

R17 = 56Ω

R19 = 1k

R20 = 47Ω

R21 = 220Ω

P1 = 20kΩ preset, multiturn, vertical mounting

Capacitors

C1,C2 = 22pF

C3-C6 = 100nF

Semiconductors

D1-D10 = 1N4148

D11 = 1N4001

D12 = LED, 5mm diam.

T1,T2 = BC337

IC1 = 74HC04

IC2 = PIC18F4580-I/P, programmed, Elektor SHOP # 060092-41

IC3 = 7805

Miscellaneous

Bz1 = AC buzzer

X1 = 10MHz quartz crystal

Graphic LC display, 128 x 64 pixels, e.g. DEM128064A or NLC128x64 (Conrad  Electronics # 187429)

Case 186 x 123 x 41mm with compartment for 9V battery, e.g. Strapubox (Conrad Electronics # 522775)

S1-S5 = pushbutton Multimec RA3FTL6 w. knob AQC09-24.2

S6 = on/off switch

9-V battery clip

5 wander sockets, screw mount (for connection to I1-I5)

Kit of parts incl. case: Elektor SHOP # 060092-71

PCB layout: free download from www.elektor.com, file # 060092-1

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