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What chip might this be?

Discussion in 'General Electronics Chat' started by kinarfi, Feb 17, 2018.

  1. kinarfi

    kinarfi Well-Known Member

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    I got a "head light" I got from friend and it didn't work, I traced the circuit and came up with what works, but one chip was not identifiable.
    It's designed to worn on the head and has 3 lights on it, the head light, the 4 lights for long distance and the tail light. Starting with every thing off, first push on the button turns on the head light, 2nd push turns on the 4 lights while turning off the head light, 3rd push turns the head light back on, 4th push makes head light and 4 lights flash, 5th push turns everything back off. The tail light is on constant when either of the other light are on.
    I would like to know what the control chip is.
    Thanks,
    Jeff Capture.JPG HEAD LITE .jpg
     
  2. dknguyen

    dknguyen Well-Known Member

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    Either it's a ridiculously specific custom ASIC made specifically for that board or much more likely, it's an 8-pin microcontroller because only only an 8 pin micrcontroller could economically contain that functionality if you're churning out less than tens of thousands of these things (even that quantity might not be enough for it to be economical). That would mean that Pin 4 is reset. 1 and 8 are power.

    EDIT: Yup. Quick search of datasheets on Digikey for 8-pin microcontrollers came up with this MCU whose pinout matches
    http://ww1.microchip.com/downloads/en/DeviceDoc/40001723D.pdf

    It has an unconventional wire up where pin 1 is not directly connected to power. Instead, it's drawing power through the Vpp/Reset pin 4 through a particularly small pull-up resistor. The cap across pin 1/8 is the decoupling cap. I wonder if anyone knows why they would go out of their way to do it like that since it doesnt seem like it would save on cost. Did you mistrace pin 1?

    In any case, it doesn't matter what the chip is specifically anymore because even if it was an ASIC you could replace it with that microcontroller and get any circuit behaviour that you want. With an unused pin 3 you could do whatever you want. There is an ADC and UART and a bunch of other stuff crammed into that thing. Quite impressive.
     
    Last edited: Feb 17, 2018
  3. JonSea

    JonSea Well-Known Member

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    It may well be that 8 pin Microchip part. But unless you are going to write your own code for it, it doesn't matter - a non-programmed part won't do a thing for you.

    There is only one way to get a replacement. Buy the exact same LED headlamp, and take the chip out of it.

    As Big Clive on YouTube (recommended) will tell you, almost anything you tske apart from China will have "the generic, mysterious 8 pin chip" inside.
     
  4. dave miyares

    Dave New Member

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  5. Les Jones

    Les Jones Well-Known Member

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    It could be a microcontroller from some other manufacturer. (Possibly Chinese.) I have lookes at the pinout of the Atmel ATtiny 8 pin chips and it does not match their power pins. I agree with dkuguyen that writing code to use one of the PIC12F or 8 pin ATtiny range would be the easiest solution. The tracks on the board could be cut and wires added to use the suggested microcontrollers.
    Edit. It is possible that the control chip could be OK Have you tried cutting the tracks to the mosfet gates in case they have gate to source shorts. You could then look at the signals on the output pins.

    Les.
     
    Last edited: Feb 18, 2018
  6. kinarfi

    kinarfi Well-Known Member

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    This makes no practical sense to damage a new unit to fix broke unit, you're liable to end up with 2 damaged units.IMHO
    I suspected that the chip would be preprogrammed chip as suggested in previous posts, but the failure was in a PFET and was replaced with a TO92 after removing the damaged components. Works good now.
    Thanks for the information, unfortunately, I am not educated in the use of PIC chips or MCU chips, yet!!
    Jeff IMG_20180206_175150_1.jpg
     
  7. JonSea

    JonSea Well-Known Member

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    Ummmm....that was kind of my point :) If the 8 pin chip is blown, it's going to take more effort than it's worth to make it work.

    That's not to say the thing is worthless. Replacing most of the electronics with a toggle switch still results in a functioning flashlight.
     
  8. dave miyares

    Dave New Member

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  9. kinarfi

    kinarfi Well-Known Member

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    I'm pretty certain that I have all the traces correct, pin 3 has no connection, pin 8 goes to ground, pin 1 goes to the cap and pin 4 goes to + power via 100R, that seemed strange to me,
     
  10. dknguyen

    dknguyen Well-Known Member

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    You could also use a PICAXE. Basically the same thing but sold with an abstraction layer to make things more accessible to beginners.
     
  11. hyedenny

    hyedenny Member

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    Could it be some kind of counter, or decoder, or multiplexer?
     
  12. kinarfi

    kinarfi Well-Known Member

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    The chip was good, what ever it is and the BS250p PFET is working good.
    Thank you all,
    Jeff
    IMG_20180219_103725.jpg
     

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