Audio level indicator using LM339

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.

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Logic Probe with 7 Segment Display

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”.

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Light sensitive alarm using LDR

Light sensitive alarm using LDR

This light sensitive alarm is very simple and works using, as main components, a transistor, an LDR and a relay.

The alarm activates when the illumination level changes from almost total darkness to a moderately high illumination level. When this happens the alarm is locked and the alarm signal, be it a light or a sound, remains active.

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