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  • Basic (PWM) Motor Speed Control Using 555 Timer ICs

    Hi i'm not really sure how to point out exactly whats wrong in your setup. It would be better if you have seen the waveforms using an oscilloscope. Also take note that the duty cycle output of IC1 should be between 90%-100%. One possible reason is that your power supply might not be able to supply the needed current of the motor or your PWM signal prior to the transistor is very low (around < 20%). Also, may i know the actual frequency of operation of your setup?

    Hi,If you use a 66% duty cycle output for IC1, then you have 44% of the time that it is LOW. Then there will be AT LEAST 44% of the time where the PWM signal from IC2 will be HIGH. Then your duty cycle range for the PWM control will be only be 44% to around 95%. The reason that the LOW duration of IC1 output should be minimized is to achieve a much lower minimum duty cycle for the PWM control of the Motor

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  • Basic (PWM) Motor Speed Control Using 555 Timer ICs

    The 20k ohm resistor is just a pull-up mechanism. This can be ignored in most instances.

    Hi, the transistor provides the needed drive current for the motor. This is important especially when your load could take up high current and the IC (LM555/NE555) might not be able to provide.

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