4017 overheat-shorting out problem

Discussion in 'The Projects Forum' started by magnet18, Jan 15, 2011.

  1. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    Hi there guys, the inner workings of most ic's are mystery to me, so what kind of pin input combination would be required to get a 4017 cmos ic to get really, really hot, really fast? im trying to troubleshoot where its shorting out, because it worked a few weeks ago...
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Do you have any of the OUTPUTS connected directly to Vdd or Ground?

    Are any of the INPUTS "floating" or not connected to anything?

    See a datasheet to determine which pins are the inputs and outputs. Any of the above will cause big problems.
     
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  3. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    just did a quick probe with the o-scope, i think the problem might be in the signal generator, would a constant-non pulsed 10v into the pin14 clock-input cause problems?
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    Unless I can see a schematic, I won't be of much more help - nor will anyone else.

    You don't say what the Vdd is, or if the clock is applied even when the Vdd is off, or anything.
     
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  5. Wendy

    Moderator

    Mar 24, 2008
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    A common mistake is to connect pin 12 (which is an output to Vcc or Gnd).
     
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  6. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    sorry, my bad
    [​IMG]
    i know the circuit, as laid out, works fine, I've been using it, more information about it is available here

    note, the site and its contents aren't mine, im just basing my stuff off the schematics
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    Wiring error is a very probability, that or the circuits you are feeding from the outputs (which are not shown on your schematic). If an output is shorted somehow that will generate a lot of heat, and the chip will be ruined.

    I remember you now.

    4017 CMOS interference
     
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  8. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    Haha, yea, i love these 4017's when they work, but they can be a pain :p
    i dont know if this is part of the problem, or if its a result of the ic failing, but the 3 output is always somewhat high, im inclined to believe that its from the ic failing because it is happening to both simultaneously, and s far as i can tell there are no shorts.
     
  9. Wendy

    Moderator

    Mar 24, 2008
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    It is possible the part was static zapped. During the winter it is more of a problem than during the summer.

    ElectroStatic Discharge

    Could you show the circuits you are driving?
     
    Last edited: Jan 16, 2011
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  10. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    Its possible, though that usually isnt a problem for me since any sttic usually jumps to my stainless steel desk before i touch anything else, which raises another question ive been meaning to ask, should i have my desk grounded (im guessing yes) how should i ground it, and if i ground it would it be usable as a ground when prototyping circuits or will there be too much interference picked up by it?

    (and yes, im sure that the desk isn't shorting out the circuit, i have a rubber pad [mousepad :\ ])
     
  11. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    sorry, for some reason only the first line of your post registered...
    the circuit im driving is the one on the left, not much to it
    [​IMG]
    after the nixie cathode comes the nixie, followed by a resistor, and then a transformer, 10K ohm resistor for the moment, 180V @ 12mA output from the transformer.
     
  12. SgtWookie

    Expert

    Jul 17, 2007
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    What is your Vdd?

    I see in the text on the page you linked to, the base resistor for the MPSA42 transistor is 33k Ohms. If your Vdd=15V, then your base current will be (15v-0.7v)/33k = 0.433mA, which would be enough for up to 4.333mA collector current. However, if you're using 5v for Vdd, then it would be (5v-0.7v)/33k = 0.13mA, and you could only sink up to 1.3mA cathode current without risking that the transistor would come out of saturation.

    Now you seem to indicate that you're using a 10k resistor on the plate. 180v / 10k Ohms = 18mA, which is likely far too much current for your Nixie tube; it should probably be around 2mA, but check your datasheet to find out. Have you measured the cathode current?

    [eta] I've never worked with Nixie tubes; but have used a number of pieces of test equipment (usually ancient frequency counters) that used Nixies for displays.

    I don't know how much voltage they drop once the gas is ionized - and that will be specific for your particular Nixie tubes.

    Ronald Dekker has a number of Nixie clock projects on his site:
    http://dos4ever.com/
    ...along with lots of other cool stuff.
     
    Last edited: Jan 16, 2011
  13. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    Yea, i need help on the supply voltge also, i found a couple datasheets...
    http://download.elektronicastynus.be/57/in-14_datasheet.pdf
    http://tubehobby.com/datasheets/in14.pdf
    but i couldn't find any information on the voltage drop...
    My transformer is supposed to be 11-26Vdc in, 180Vdc @ 12mA out, the tubes should be 170V @ 2-2.5mA
    Also, for my Vdd, my wall wart is *SUPPOSED to put out 12V, how much it puts out without anything connected to it is actually 16 V, i just realized this just now when i measured it to be sure, im changing to a better one...
     
  14. Wendy

    Moderator

    Mar 24, 2008
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    Your transformer has DC out? I don't think I've ever seen a wall wart with 180VDC out, and a transformer isn't DC, some circuitry is required. Clarification please?

    16 VDC is OK for CMOS. The wall wart voltage will go down with loading, as this is what it was intended to do. Most wall warts are not regulated, so this is pretty typical, and I don't think it is a problem. If it is a simple regulator will take care of it.
     
    Last edited: Jan 17, 2011
  15. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    sorry, for my vdd for all the logic and to power the nixie transformer im using a wall-wart with 12(16)Vout, for the nixies i have a separate transformer that i bought.

    As for the internal circuitry, im not sure whats in it, i would guess a flyback converter but i really have no idea.
     
  16. Wendy

    Moderator

    Mar 24, 2008
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    OK, confusion solved. That is a DC-DC converter, not a transformer.

    Have you wired this to a permanent circuit yet? I'm wondering if a transistor is wired wrong (or failed under the high voltage) and feed some voltage back into the 4017. Normally this can't happen, but with component failure anything can happen.

    Maybe some pictures of the board top and bottom?
     
  17. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    ok, i have definitley identified a problem with the signal generator, which was also the board thetransformer was on, i actually just removed it, im going to put it on a separate board
    give me a few minuets and ill upload some pics of all the boards
     
  18. SgtWookie

    Expert

    Jul 17, 2007
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    Bill,
    That's where I was going with the transistor coming out of saturation.

    It wouldn't hurt to throw a 7812 and a couple of caps on the in and out sides for regulation of Vdd. Transient spikes can and do happen; a regulator would help prevent damage.
     
  19. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    ok, i need to run, ill have to upload the pics at around 9'ish
     
  20. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    Alright, these are the pics of the signal generator circuit, at the moment when i have approx 15-16 volts in i get a steady 9 volts out, not the pulsed 1Hz i was getting before, this problem appeared after the 4017's were smoked, because it was driving them properly when they were overheating.
    the transformer was originally on this board but it was only electrically connected via the ground
    probing with the o-scope shows no oscillations anywhere that i can detect, but my probe cant read the signal coming right out of the crystal
     
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