# Oscillating with the 74HC14

Today, I built an oscillator with the 74HC14 hex inverter Schmitt trigger.

Here’s the datasheet.

I thought this was interesting, the inventor of the Schmitt trigger, Otto Herbert Schmitt (1913 – 1998), was a scientist who worked both in physics and biology. He figured out the trigger while studying neural impulse propagation in squid nerves.

I built this circuit with a capacitor 0.01uF and resistor 14.8k, which were just lying on the bench. I calculate a frequency of about 6.75kHz. Freq (Hz) = 1/ (R*F)

Which is pretty close to what shows on the oscilloscope … I’m looking at the output signal on pin 12.

Time (seconds) = 1/Frequency (Hz)

I then used all the gates available and made three oscillators. By using different values for R (Mohm range) and C (uF range) on each oscillator, and therefore creating three out of phase oscillators, I was able to get a nice color cycling effect on an RGB LED.

## 3 Comments

## lamin ceesay

November 4, 2011very interesting little project. i just have a quick question on how u got your frequency.

you stated freq = 1/(C*F)

am guessing c = capacitor and F = resistor and * = multiplication yes/no . if yes then

1/(0.01uF * 14.8K) = 1/(148^-6) = 6.75KHz

please help me correct my way if am wrong. thanks

## Sophi

November 6, 2011hello-

Good catch- you are correct, and I have corrected the 2 typos.

If you look at the oscilloscope, each square is 100us.

You can see that a full cycle is just under a square and a half, say 150us.

Frequency = 1/cycle = 1/(150*10^-6) = 6666.66Hz =6.7kHz

## ed

August 27, 2014i understood the formula to be in this case: 1.2/(RC) and in that case it would be 8.1 kHz