November 2000
Intermediate to advanced
336 pages
7h 43m
English
Content preview from Radio and Electronics Cookbook
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12
An LED flasher
Introduction
The LM3909 is an integrated circuit (IC) which will flash a light-emitting diode (LED). Using only two extra components and a battery, the circuit is cheap and has a very low current drain from a 1.5 V cell. The circuit can be used as a novelty flasher, an indicator for a dummy alarm bell box, or it could be attached to a torch so that it could be found easily in the dark! The simple circuit is shown in Figure 1.
Figure 1 Circuit diagram of the LED Flasher. Pins 1, 3 and 7 of the IC are not used
Assembly
The circuit can be built on a small piece of Veroboard (the piece shown in Figure 2 measures 15 holes by ...