Chip ID In Dual Shift Reg/Darlington Circuit?

Discussion in 'The Projects Forum' started by IowanChef, Apr 9, 2010.

  1. IowanChef

    Thread Starter Active Member

    Mar 6, 2010
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    I picked up this really interesting but cheap-looking lamp from the thrift store the other day, and basically it's 24 LEDs (8 each, R,G,B) connected to two M74HC595B1 8 bit shift registers and two ULN2003AG Darlington arrays. However, there's one 18 pin DIP chip in the heart of the circuit with no markings whatsoever. The board itself is white and hard to track much of anything on, but I can see a 12mhz crystal with three small ("30") ceramic caps, one bigger electrolytic (100uf), and a three-terminal LM7805 positive voltage regulator.

    Any idea what this could be? I'm a complete newb (with persistence!) and have guessed it to perhaps be a PIC of some sort, like maybe a PIC16F88 or the sort? I don't have a lot of things to test it out with, but I DO have a lot of chips. Only thing that matches up just on a "hey, this has 18 pins too!" kind of way and after some Googling is the PIC16F88.

    Thoughts? Thanks in advance for any and all help.


    Cheers.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Well, the 12MHz xtal with the cer.caps gives you the clock rate, but good luck figuring out what the uC is, AND how it's programmed. There are many other uC manufacturers besides Microchip.
     
  3. IowanChef

    Thread Starter Active Member

    Mar 6, 2010
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    Gracias SgtWookie.

    I goofed in my initial listing. It's ONE 8 bit shift register, two Darlington arrays, and it looks like the 12mhz oval metal crystal resonator (?) is connected to pins 13 and 14 of whatever this 18 pin thing is that's controlling it. Two per red, green, and blue LEDs on four quadrants of the lamp circuit, and they cross-fade (three push-buttons select various speeds, pause, and power on/off, respectively) to create all the wonderful colors that red, green, and blue LEDs do..

    Anyway, thanks again. The search continues..
     
  4. retched

    AAC Fanatic!

    Dec 5, 2009
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    Yeah, It is a fruitless pursuit to try to discover the type of uC in the lamp.. After all, it doesn't REALLY matter. If you wanted to re-create the lamp, about any uC will do.

    If you wanted to RE-USE the chip, that will be unlikely.. Even if it happens to be an off-the-shelf PIC, It is most likely code-protected and you will have little chance of using it.

    Now if this is just for disection reasons.. for education, You can start by looking up the billion 18 pin uCs available to see which ones use pins 13 and 14 for the clock pins.

    But then again, Even if you figured out the chip, you would have no idea of the code programmed on the chip....

    .Have fun any way...
     
  5. IowanChef

    Thread Starter Active Member

    Mar 6, 2010
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    Yeah, I'm certainly "having fun" with it, meaning I stayed up cussing and delicately desoldering it from it's beautifully-crafted board. There was a layer of white sealant over the board ("drawn by YIM") that I gently sanded away after realizing I'd completely destroyed the little coil braces you find in the holes of these boards. Is there an easier way to remove chips from these kinds of constraints? Because after you've finally pried the sucker loose after NOT managing to fry it, you really tend to destroy the traces connecting to them. I'm re-running these traces with some header pins and fine-gauge wire, hoping I can at least make it function as it initially did, having not learned a damn thing by removing the chip in the first place.

    It's really quite remarkable how you can spend an entire day and end up completely empty-handed.

    Retched, once again, thank you. Slightly OFF-TOPIC, I also gave up on trying to use the Crystal Trackball as-is and will just strip it to the rotary encoders, being that quadrature is considerably easier a concept to veer into. Being only months into this very new territory, I'm avoiding microprocessors at all costs in hopes of learning the sticks and stones of it all..

    I think I'm on this site daily, if not hourly. Thanks to you all. Sincerely.

    Jrm
     
  6. retched

    AAC Fanatic!

    Dec 5, 2009
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    If you start, trying to learn microcontrollers, then retire to learn the basics first, when you return to microcontrollers, they make alot more sense.

    I think my english teacher would slap me after reading the above sentence.
     
  7. IowanChef

    Thread Starter Active Member

    Mar 6, 2010
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    Well Retched, I took a day off from that circuit, returned to it, and it never really returned to its former glory. While I really waited to pry that chip off, because I loved it for what it was, without any modding, I did learn some things. And besides, those lamps show up in thrift all the time.. Thanks again for chiming in.
     
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