Apr 062017
 
Car Burglar Alarm using two 555 timers

Car Burglar Alarm using two 555 timers

This is a simple Car Burglar Alarm circuit that uses a dual contact relay and two 555 timers, each of them working as a monostable multivibrator.

The alarm will activate the car horn, approximately 5 seconds after either door is opened and has not been properly closed.

Apr 042017
 
1 Input - 4 Outputs Stereo Audio Splitter

1 Input – 4 Outputs Stereo Audio Splitter

This 1 Input – 4 Outputs Stereo Audio Splitter has a single input and 4 independent outputs, each amplified with an operational amplifier.

Each operational amplifier is configured as an emitter follower, to take advantage of its high input impedance and low output impedance, thus avoiding distortion in sound.

Mar 282017
 
Audio level indicator using LM339

Audio level indicator using LM339

This audio level indicator using LM339 circuit is very interesting, because it allows us to visualize the audio level intensity by connecting this circuit to the output of a loudspeaker.

The LM339 integrated circuit has 4 comparators that operate completely independently but share the same voltage source.

Mar 212017
 
Logic Probe with 7 Segment Display

Logic point using 7 segment display

This logic probe with 7 segment display is designed with TTL technology and does not use LEDs to display the high and low logic levels found in many of the logical probes on the market. The circuit shows the capital letter “H” when there is a logical “1” or the letter “L” when there is a logical “0”.