- on Miscellaneous Electronics
- Published in issue 7/2001 on page 0
Pulse Edge Visualiser
A digital signal must have a certain duration before it can be monitored using an LED. Short pulses cause the LED to flash for an interval that is too short to be registered by our ‘slow’ eyes. The small supplementary circuit described here, which consists of only four two-input NAND gates in the form of a 74HC(T)132, two resistors, a diode and a capacitor, lengthens a short pulse enough that it can be clearly recognised using an LED.The output level at pin 8 prepares the circuit for the subsequentpulse edge. If a logic ‘1’ is present at the output, C1 will be fully charged and the output of gate 1a will be Low.