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Programmable Continuity Tester to Build 2015-04-13

  • Will not see diodes and other semiconductors as shorts ...
  • Programmable thresholds of resistance to measure using multi-turn trimmer
  • Responds to continuity of a few ohms or kilo ohms denoted by setting of trimmer
  • Audible indication via buzzer and visual by virtue of an LED
  • Low Cost & Easy-to-Build
  • Voltage clamping protection from accidental measurement of voltage
  • Power switch and low power consumption

:: PCB :: (See attached for PDF @100% size to print from laser printer)

:: PCB Overlay Parts Placement ::

:: Parts List ::

IC1 LM393
IC2 LM78L05
D1-D2 1N4007
D3 7V5 Zener
Q1-Q2 BC547
Q3 BC557

2 x 10K
1 x 100R
1 x 470R
1 x 220R
1 x 2K2

1 x 10uF
1 x 100nF

8-Pin IC Socket
SW1 Slide Switch SPDT PC-Mount
VR1 50K 25-Turn
Red LED 5mm
5 Volt PC-Mount Buzzer (Internal Driver Circuit)
Black Alligator Clip (32mm)
Red Alligator Clip (32mm)
9 Volt Batery Snap Connector
250mm Length of 26AWG Red Hookup Wire
250mm Length of 26AWG Black Hookup Wire
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