Position: Index > Unclassified >

Logic Probe With Sound(BC548)

2017-08-06 12:40  
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.

This article describes the Logic Probe With Sound (BC548). The principle is very simple, very practical. The circuit components can help you understand better grasp this principle. For example, in this circuit, you can go to find and buy these components: BC548.

This logic probe can be selected to operate onTTLorCMOSlogic levels, depending on switch S1. A string of resistors associated with switch S1 sets the threshold levels for a window comparator comprising IC1a and IC1b. Depending on whether the level applied to the probe is high or low, the window comparator turns on LED1 (high) or LED2 (low). The 1.2M and 680k resistors set the probe signal to a midrange value when the probe is open-circuit, thereby preventing eitherLEDfrom being lit.

Circuit diagram:

 

Figure:1 Logic Probe With Sound

Figure 1 Logic Probe With Sound


If a pulse signal is present, the output of IC1a will toggle the clock input of flipflop IC2a. This drives LED3 which either lights for each pulse or continuously, depending on the setting of switch S2. Finally, the outputs of IC1a & IC1b are connected by diodes D5 & D6 to the base of transistor Q1 which is connected to the Reset input of flipflop IC2b. This has a piezo sounder (not buzzer) connected between its Q and Q-bar outputs so that it produces a sound which echoes the input pulse signal.

 


Reprinted Url Of This Article:
http://www.eeweb.com/blog/extreme_circuits/logic-probe-with-sound