Circuit Board Tester (BC557)

2016-01-26 11:09  
Declaration:We aim to transmit more information by carrying articles . We will delete it soon, if we are involved in the problems of article content ,copyright or other problems.

Indicates the basic integrity of a printed board

Circuit diagram:

Circuit Board Tester


R1,R2___________22K  1/4W Resistors

D1______________LED  (Any dimension and shape, preferably red)
D2______________LED  (Any dimension and shape, preferably green)

Q1____________BF245 or 2N3819 General-purpose N-Channel FET
Q2____________BC547   45V 100mA NPN Transistor
Q3____________BC557   45V 100mA PNP Transistor

Probe_________Metal Probe 3 to 5 cm. long

Two Miniature Crocodile Clips (Red and Black)

This little circuit indicates the basic integrity of a printed board, detecting 0V, positive supply voltage from less than 3V to 30V and floating parts.
If the probe is floating, as it would be in a broken track, then both LEDs barely light up, since there is no current to drive the transistors, but if the probe touches 0V or a positive voltage one or other lights. A digital signal should light them in proportion to the mark-space ratio whereas the output of a circuit oscillating at a frequency rate below about 20Hz will cause the LEDs to flicker alternatively.
The LEDs will illuminate always at a constant intensity, no matter the voltage supply used, because they are fed by a very simple Fet constant-current generator (Q1).

This article describes the Circuit Board Tester (BC557). The content is very simple, very helpful. Components in this article can help you understand better understanding of this article. For example, in this article, you can go to find and buy these components:BC557.

Reprinted Url Of This Article: