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What's a good circuit for a Schmitt trigger flasher? Answered

I have been told that a Schmitt trigger can flash an LED, just like a 555 timer can, only the circuit is simpler. I haven't been able to find an example of this online, however.

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anachrocomputer (author)2009-03-17

You can make a single Schmitt trigger gate into an oscillator by connecting a resistor and a capacitor. It must be an inverting gate such as a NAND or NOT gate. An example is on page 177 of the Practical Electronics Handbook, by Ian Sinclair:

http://books.google.co.uk/books?id=Hci_D7Yh8UwC&pg=PA177&lpg=PA177&dq=7413+oscillator+schematic+-555&source=bl&ots=-8BiMeAfEG&sig=Esyx-0mer2vfGWWTdeqKmcvBPHk&hl=en&ei=jbW_SaStCdyLmQeU_oGjDw&sa=X&oi=book_result&resnum=7&ct=result

The 7413 chip has four Schmitt NAND gates, and the 7414 has six Schmitt inverters. For non-5V circuits, try the 74HC13 and 74HC14, or the CMOS 4000-series chips CD4093 or CD40106.

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Swishercutter (author)2009-01-31

You are looking for a Schmitt trigger oscillator. Here is a page full of different oscillatorsoscillators.

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mattikariluoma (author)2009-01-28

Hack-a-day has a very good example of using a schmidt trigger:
http://www.hackaday.com/2008/05/01/how-to-make-a-digital-synthesizer/

I'd just replace the speaker with an led, and bam!

as a side note, the IC used in that article actually has 6 Schmidt triggers built in, so you could have many flashing leds. all you need is one resistor and one capacitor per led, plus power.

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collard41 (author)2009-01-28

I could think of a circuit with a Capacitor and a Schmitt trigger, but i think this may be of use. it uses 2 NOR gates (4 in a single chip) a resistor and a capacitor to give pulses. the frequency can be changed with different resistor and capacitor values.

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