Schmitt Trigger | Electronic Project Circuits

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LM555 Timer Used As A Voltage Comparator Or Schmitt Trigger

The next section shows how the LM555 timer could be used as a voltage comparator or a wide offset Scmitt Trigger. Applications for which it is not particularly well suited but one that is in wide use with model railroaders.
Shown on the schematic is a secondary output that uses the open collector at the DISCHARGE terminal (Pin 7) of the timer. This output can sink up to 200 milliamps and would be ideal for driving relays.
The main disadvantage to using this circuit is the the large dead-band (1/3Vcc) between upper and lower threshold voltages. An optional resistor, R5, can be added to the circuit to lower and compress the detection voltage range but this only partially alleviates the problem. [...]

Read more source: http://home.cogeco.ca/~rpaisley4/LM555.html

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Categories: Digital Tags: LM555 Timer, Schmitt Trigger, Voltage Comparator

Light Sensitive Switch with LDR + 2N2926

This be circuit warn when be become dark, or Light sensitive switch. By use electronics part the base is important , be the transistor 2N2926 and AC128. For the light sensor also LDR (light dependent resistor) or a resister quickly the light. When have no the light makes Q1 , stop work. The Q2 and Q3 then work, It then send current give buzzer utter loud immediately. By circuit arrangement of Q1,Q2 be the character of Schmitt trigger help testify modify analog signal to digital 2 the level well. And help decrease the condition disturbs all with. The detail is other , see in the circuit.

Circuit Light Sensitive Switch with LDR + 2N2926