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  1. #1
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    I need help identifying these diodes

    Hello everyone,

    I have a bunch of diodes of the SMD type packaged in tape and I believe they are more than 500. As far as I remember, they were ordered by a mistake so I put them aside. They were kept in an anti-static plastic bag without any markings, PNs, or anything else that could help in identifying them.

    As you can see in the following photos, they look like a Schottky or normal signal diode and the voltage drop across it is 0.550V.

    Now, I was wondering if I can use this type of diode in a full-wave bridge rectifier circuit to rectify 220V mains. This way, I can utilize them for something useful.

    Click image for larger version. 

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    Thanks in advance!

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    Re: I need help identifying these diodes

    Those are little, black, cylindrical diodes.

    You can't seriously expect anybody to tell you anything more about those. Maybe they are red LEDs.



    •   Alt16th May 2018, 22:14

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    Re: I need help identifying these diodes

    They are MELF packaged but the only other identifying characteristic is the color of the cathode band. If it is silver it is probably an LL4007 which is a standard recovery diode rated at 1KV/1A. I have identical ones here. Use at you own risk though, there might be other devices with the same marking.

    Brian.
    PLEASE - no friends requests or private emails, I simply don't have time to reply to them all.
    It's better to share your questions and answers on Edaboard so we can all benefit from each others experiences.


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    Re: I need help identifying these diodes

    Hello e-music,
    Schottky diodes normally have a lower voltage drop across them to what you've indicated.
    I think Brian is correct in regards to them being general purpose rectifying types.
    If you can, get a transformer with a low secondary output and make a full bridge rectifier
    circuit and see how the diodes will tolerate it over time.
    Connecting them directly to mains I would personally avoid, due to the fact that if they are
    the Schottky type, I doubt they could withstand the peak reverse voltages generated by
    direct AC mains connection. They would still work OK at lower AC voltage, but they will
    heat up more than GP type diodes, as well as introduce extra noise due to their faster
    switching speeds.
    They definitely don't look like small signal diodes, and very doubtful they will be Zeners.
    Regards,
    Relayer


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    •   Alt17th May 2018, 01:16

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    Re: I need help identifying these diodes

    Only way to really tell, is if you have access to a curve tracer.
    That way, at least you can determine Vf and Vbr.

    Since there is no way that you could measure recovery time, I would not use them other than low frequency AC rectification.
    My batteries are recharged by "Helpful Post" ratings.
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    Re: I need help identifying these diodes

    Quote Originally Posted by barry View Post
    Maybe they are red LEDs.
    Red LEDs? Well, it could be difficult to identify them, but I'm pretty sure they are anything but "Red LEDs"! I have never seen a Red LED without a lens and packaged in such a way! :))

    Anyways, thanks for the info!

    - - - Updated - - -

    @Brian:

    Thank you. Yes, the band is in silver.

    - - - Updated - - -

    @Relayer:

    Hi Relayer,

    Thank you very much for the input. A detailed and very helpful one, as usual!

    Yes, and I believe they are GP rectifiers, too. I believe the only way to verify is to build a full-wave bridge and check them in circuit for some time. I'm working on a project that needs power directly off the mains and a Transformer-less PS is the only way for me to keep size and cost low for the board. I thought I could use them for the bridge-rectifier and save a little. Otherwise, a bridge rectifier in a single package is much better.

    Thanks again!

    - - - Updated - - -

    @schmitt trigger:

    Thank you for your reply. Yes, I had that in mind initially. I wanted to use them in a bridge rectifier configuration to rectify 220v/50Hz mains.



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    Re: I need help identifying these diodes

    Well, it was laying on a schematic right next to a component that said "LED red".

    But, seriously, I would hesitate to hook up an unknown component to 220V. Just go buy four 500V rectifiers; they're about $0.10 each.



    •   Alt17th May 2018, 22:08

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    Re: I need help identifying these diodes

    @ barry:

    In fact, it's about 700 of them, not four. And I need to populate a big batch of boards I plan to build with these diodes. Nevertheless, I agree with you. Even $70 is not a big deal to order the correct diodes for my circuit.

    By the way, the schematic in the photo has nothing to do with this circuit or the diode concerned!

    Thank you again for your reply!



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    Re: I need help identifying these diodes

    Quote Originally Posted by e-music View Post
    @ barry:

    In fact, it's about 700 of them, not four. And I need to populate a big batch of boards I plan to build with these diodes. Nevertheless, I agree with you. Even $70 is not a big deal to order the correct diodes for my circuit.

    By the way, the schematic in the photo has nothing to do with this circuit or the diode concerned!

    Thank you again for your reply!
    I am just astounded. You are apparently building something to actually sell to customers, and you seriously considered building them out of parts that you DON'T KNOW WHAT THEY ARE? I hope you have good liability insurance.



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