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  1. #1
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    Protection circuit help

    Input will be either Battery: 9V DC or 24V DC.

    Output: 3.3V DC

    For battery operation, It has ON/OFF circuit. When the button is pressed, Transistor will provide supply to the Regulator. Again if the button pressed, it will power OFF. It also has a option that, when the signal from the Micro controller is applied, it will power OFF.
    Please check the attached circuit.

    Does this circuit has Overvoltage, Overcurrent, Short circuit, Reverse battery protection, EMC, etc?Please help

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    Re: Protection circuit help

    That (goofy) circuit has none of the features you mention, other than the inexplicable rectifier bridge on the 24volt input. Why would you have a bridge on a DC input? Is it, perhaps AC input? What insures that when you first plug in your battery, the transistor is driven off? The input to U4A is indeterminate on power up.



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    Re: Protection circuit help

    NO AC input.

    Only 24V DC or 9V battery. What are the components to be added to add those features? Please help.



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    Re: Protection circuit help

    Overvoltage: SCR crowbar; BJT/zener clamp; overvoltage protection IC
    Overcurrent: Fuse; circuit breaker; regulator with built-in current-limiting; current-sense resistor and BJT current limiter
    Short Circuit: Isn't a short-circuit the same as an overcurrent???
    Reverse battery protectcion: diode
    EMC: Foil; ferrites; metal case; capacitors; resistors


    All of the above: do an internet search.


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    Re: Protection circuit help

    MIC5236 has overcurrent protection and reverse battery protection.

    Voltage protection upto –20V to +60V.

    that's why I didn't add any external components. Regarding EMC, I don't have knowledge in that. Can you help me to design it.
    Please clarify



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    Re: Protection circuit help

    Quote Originally Posted by hemnath View Post
    MIC5236 has overcurrent protection and reverse battery protection.

    Voltage protection upto –20V to +60V.

    that's why I didn't add any external components.
    So, if you knew the answer, why did you bother asking the question?

    As far as EMC, you need to be a LOT more specific. Different countries have different requirements. And it depends on the type of equipment, and where it's used.



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    Re: Protection circuit help

    Quote Originally Posted by barry View Post
    So, if you knew the answer, why did you bother asking the question?
    Thanks for your reply. I'm not sure whether the inbuilt features in the IC is enough or should I have external components. That is the reason I had a doubt.

    Regarding EMC, I'm from India. Pressure gauge and to be used in process industries.



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    Re: Protection circuit help

    You do things like putting common-mode chokes on the power inputs, but if you’re going to be selling this product, you’ll probably need to have it tested by an outside lab. I believe in the EU you can ‘self-certify’; I don’t know what the regulations are in India. Since this doesn’t have any high frequency signals, it shouldn’t be too much of a problem meeting the requirements.



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    Re: Protection circuit help

    Funky startup circuit indeed!
    Have you actually tested it in a breadboard?

    You are pulling U4’s output to Vbat-Vf, roughly 23 volts, from an IC which is presumably powered by 3.3 volts. Really?
    My batteries are recharged by "Helpful Post" ratings.
    If you feel that I've helped you, please indicate it as a Helpful Post



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