How to Make a Doorbell Circuit for Deaf People?

How to Make a Doorbell Circuit for Deaf People?

Doorbell for Deaf People.

When a deaf person is alone in a house, it would be very difficult to realize that someone is knocking on the door without any visual warning signal.

The main component for the Doorbell for the deaf circuit is the CMOS 4001 integrated circuit, which has four two input NOR gates

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How to Make a Current Flow Indicator?

How to Make a Current Flow Indicator?

This Electric Current Flow Indicator gives a visual indication that there is a current flow. Possible applications for this small circuit may be: a battery charger, a voltage power source, etc.

In order to achieve our objective we place 3 rectifier diodes in series, which in turn are in series with the load / battery.

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Temperature gauge circuit using LM324 IC (PCB)

Temperature gauge circuit using LM324 IC (PCB)

Temperature gauge circuit using the LM324 IC

The temperature level is displayed using 4 LEDs:
A green LED indicates that the temperature is OK.
Two yellow LEDs indicate that the temperature is higher than normal.
A red LED indicates that the temperature is very high

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Car battery monitor circuit using 4 LEDs

Car battery monitor circuit using 4 LEDs

Car battery monitor circuit using 4 LEDs

This simple Car battery monitor, allow us to know the voltage of the battery at all times. To achieve this 4 leds are placed somewhere on the dash of the car. Each LED has a label indicating the battery voltage at that time.

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8 LED VU meter circuit using LM324 IC

8 LED VU meter circuit using LM324 IC

8 LED VU meter made of IC-LM324.

This circuit can be used to display the variation of an audio signal in a group of 8 LEDs, behaving like a VU meter. We could use an specific integrated circuit used for VU meters, but we decided to use a readily available integrated circuit: The LM324 op amp.

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High - Low Temperature Indicator using LM35, 741 and LEDs

High – Low Temperature Indicator using LM35, 741 and LEDs

This High – Low Temperature Indicator shows us, by means of two LEDs, when the sensed temperature is above or below a set limit.

When the temperature is above the pre-set temperature level, LED D1 will light up and if it is below, LED D2 will light up.

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