Tag Archives: 555 timer


555 Contest Entry: Automatic hair drier

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Here’s another entry for the 555 contest. This project is about an automatic hand dryer that turns on when the hands are brought close to the dryer. It uses infrared diodes and a photo diode sensor to detect the presence of hands. The optical sensor mechanism then triggers the 555 timer which is configured in a monostable mode. The 555 output activates a relay switch that turns the fan on. The duration of the monostable output (fan on time) is defined by the resistance and capacitance connected to 555. Read more

555 Contest Entry: AM radio

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555 timer based AM radio receiver published on Tube Time is one of many entries for the currently running 555 contest. This project uses a 555 timer as AM demodulator plus amplifier to drive the speaker. The radio signal is tuned with an LC tank circuit. The 555 timer is configured as a PWM where a ramp signal is created with a capacitor and a potentiometer. The radio signal picked by the LC circuit is superimposed on the ramp signal which varies the duty cycle of the output PWM wave. The variation in the duty cycle corresponds to the audio signal in the radio waves. Read more

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