How can I add sounds to my logic probe?

Question

I am a beginner at electronics and I want to build a simple logic probe for TTL circuits. I found this diagram online:

Which does exactly what I want. However, I would like to make it play a high pitched sound when it is in high state and a low pitched sound when it detects a low state. I guess I would need some kind of speaker, but I don't know much about them, so basically I don't know where to begin or how to accomplish this, so any help will be appreciated.

Answer 1

You could add a piezo buzzer in series with your LED, put the high pitch one in series with the HEIGH LED and the a lower pitch in series with your LOW LED. They are quite cheap, small and work can work at low voltages so it would be perfect with to fit your circuit.

Answer 2

Google "electronic buzzers" and choose one with high pitch and one with low pitch. Here is a page from Maplin that gives some ideas: -

Here's a tri-tone one (on maplin page also): -

There are plenty on the web and they work from DC so should easily interface to your circuit.

Here's a very small one that works from 1.5 volts to 5V: -