• Resolved

Monostable Multivibrator operation for constant excitation voltage

Prodigy 30 points

Replies: 5

Views: 151


I have been trying to get the above mentioned output when triggered by a digital output signal from microcontroller. The output will be controlling an electromagnet with resistance of about 25 Ohm. The trigger pulse will activate and deactivate the electromagnet as commanded by the trigger signal. I have explored monostable multivibrator option using LM555 Timer IC. But the IC requires a short trigger pulse, not continuous voltage signal. Is there any other possible way to achieve the logic.

  • What happens when the trigger signal is 0 V? Is the desired output 0 V?

    Logic cannot handle currents more than a few milliamperes. Do you already have a circuit to drive the electromagnet, and can you show its schematic, especially how it is controlled?

  • Rajat,

    The data sheet's mono-stable circuit can provide a high output for 200ms.

    A resistor, capacitor, and diode can be added to pulse the trigger low to start the timer. After that the input can remain high indefinitely or go back low.

    Ronald Michallick
    Linear Applications

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  • In reply to Clemens Ladisch:

    Hi Clemens,

    Yes right, When the trigger signal is 0V, the desired output will be 0V.

    The logic will just control the switching power circuit which will provide the required power for the load. Although the switching circuit is not the finalized, I have added a schematic for reference.

  • In reply to Ron Michallick:

    Thanks Ronald,

    I will give it a try for sure and get back to you soon.

  • In reply to Rajat Phate:

    The 74xx123 monostable multivibrator is edge controlled; see the application report Designing with the SN74LVC1G123 Monostable Multivibrator (SLVA720). (Use the B input to always get a 200 ms pulse, or the CLR input if the output should be reset if the trigger is shorter than 200 ms.)