Become a Member
Members Only​
Article

100 mV Continuity Tester

100 mV Continuity Tester
100 mV Continuity Tester
Labs Project
Based on a Labs project | September 2024 | Find it here
Most continuity testers are very simple and therefore have simple capabilities. This design, however, is unique in several ways. Firstly, it’s based (almost) entirely on discrete components, implementing several opamp type circuits with just transistors. Secondly, this design has some very useful features, such as multiple thresholds, different audible tones and also an open circuit probe voltage of just 100 mV. This makes it particularly useful when testing for shorts in-circuit, whilst ignoring semiconductor junctions and high value capacitances. All built on a single self-contained board assembly complete with battery, switch, probe sockets, LEDs and the sounder.
Log in here as a subscriber to read the article.

Continue reading this Elektor article?​

Try a digital membership (Green) for 6 months for only €5.33 per month.​​
  • Unlimited access to online Member Only articles
  • 3 new editions Elektor Magazine (digital)
  • More than 5000 Gerber files
  • 20% member discount on e-books (at elektor.com)
  • 10% member discount on Products (at elektor.com)
Try for 6 months.
Stops Automatically.
What is Elektor Exclusive?
 

Materials

Component list

Component List

Resistors

all 1%, 0.25 W

R1, R2 = 560 Ω

R3, R15 = 1k2

R4 = 1k5

R5, R28, R31 = 1k0

R6, R12 = 4k3

R7, R39 = 10 k

R8, R10, R11, R13, R23 = 2k7

R9, R19 = 2k0

R14, R42 = 390 Ω

R16, R20, R24 = 1k3

R17, R21, R25 = 620 Ω

R18, R22, R26 = 470 k

R27, R38 = 470 Ω

R29, R30, R37 = 22 k

R32, R33 = 6k2

R34, R35 = 15k

R36, R41 = 100 Ω

R40 = 220 Ω

R43 = 10 Ω

RV1 = 10 k multiturn trimmer pot, vertical, in-line pins

 

Capacitors

C1…C7, C9, C11…C13 = 100 nF, 50 V X7R ceramic, 2.54 mm pitch.

C8, C10 = 2.2 uF, 16 V X7R ceramic, 5.08 mm pitch.

 

Semiconductors

D1…D7 = 1N4148

D8, D10 = green LED, 5 mm

D9, D12 = red LED, 5 mm

D11 = yellow LED, 5 mm

Q1, Q11, Q14, Q17 = BC327 PNP transistor

Q2...10, Q12, Q13, Q15, Q16, Q18, Q19 = BC337 NPN transistor

U1 = LP2950ACZ−5.0G, 5 V low dropout regulator (not 78L05)

 

Miscellaneous

SP1 = Piezo sounder, TDK PS1440P02BT (eg. Farnell 3212600)

B1a = Negative battery terminal, Keystone 593 (eg. Farnell 1702642)

B1b = Positive battery terminal, Keystone 594 (eg. Farnell 1650706)

B1 = Alkaline 9V battery (PP3 style).

J1 = Black 4 mm socket, Multicomp 24.243.2 (eg. Farnell 1698983)

J2 = Red 4 mm socket, Multicomp 24.243.1 (eg. Farnell 1698982)

SW1 = Slide switch, 90°, Multicomp 6MS1S3M1RE (eg. Farnell 1550250)

Discussion (0 comments)

Embed Code