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

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.

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:


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.
You are looking for a Schmitt trigger oscillator. Here is a page full of different oscillatorsoscillators.
Hack-a-day has a very good example of using a schmidt trigger:

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.
collard418 years ago
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.