Four-channel logic analyser
Digital Inspector
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.
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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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.
Component 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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