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Should my protoboard buzz? — Parallax Forums

Should my protoboard buzz?

Jake11611Jake11611 Posts: 47
edited 2007-06-09 10:53 in Propeller 1
I got my new protoboard yesterday and I finally found a 9v AC adapter in my cellar. I plugged it in, and turned on the prop. The indicator light comes on, but I'm hearing a buzzing noise coming from the prop. It's pretty quiet though. Should I stop using that adapter?

Comments

  • HenrikHenrik Posts: 10
    edited 2007-03-22 10:18
    Try feeding it with 9v DC instead! [noparse];)[/noparse]
  • ForrestForrest Posts: 1,341
    edited 2007-03-22 10:42
    The Prop Proto Board requires 6-9V DC
  • crgwbrcrgwbr Posts: 614
    edited 2007-03-22 11:43
    I think he might of meant that the adapter converts AC wall power into 9vdc.

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  • parts-man73parts-man73 Posts: 830
    edited 2007-03-22 12:27
    According to the Datasheet, LM1086 series regulators will tolerate an input of up to 25VDC. I understand why Parallax derates these numbers, it'll live a longer, cooler life at a lower voltage.

    The day I received my protoboard in the mail, I couldn't find an appropriate power supply, so after checking the datasheet on the regulator, I plugged in my laptop power supply (18 VDC) it ran fine, but the regulator got warm quickly. Since then, I've been running a more reasonable 9 volt.

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    Brian Meade

    "They who dream by day are cognizant of many things which escape those who dream only by night" - Edgar Poe
  • CJCJ Posts: 470
    edited 2007-03-22 13:03
    I would check the adaptor to see if it outputs 9vDC or 9vAC, if it says AC on the output line you should stop using it and find one that outputs DC

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    Parallax Forums - If you're ready to learn, we're ready to help.
  • Jake11611Jake11611 Posts: 47
    edited 2007-03-22 22:16
    It does put out AC! I can't believe I didn't notice that. I'm going to see if I can find another adapter...

    EDIT: I think my prop's okay. Am I correct in thinking the regulators had reverse-battery protection, and would've protected it?

    Post Edited (Jake11611) : 3/22/2007 10:29:42 PM GMT
  • CJCJ Posts: 470
    edited 2007-03-22 22:58
    I couldn't find anything about reverse battery in the datasheet for the regulators, so here's hoping it's OK

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  • Mike CookMike Cook Posts: 829
    edited 2007-03-22 23:09
    I skimmed through the data sheet for the LM1086 voltage regulator:

    http://www.national.com/ds/LM/LM1086.pdf

    Did not see anything about reverse polarity protection, nor did I see any provided on the Propeller ProtoBoard:

    http://www.parallax.com/dl/docs/prod/prop/Propeller-ProtoBoard-v1.1.pdf

    If your lucky, it MIGHT still work with the proper power adapter (+9VDC), but probably at least the first +5VDC LM1086 is toast. But I'm ASSUMING the whole board is probably fried.

    And if you had a PropPlug, PropClip, USB2SER and your PC's USB Port connected, those·might also have been hit with the AC voltage. Of course this is the worst case scenario, but it would not hurt to check everything connected for proper operation. Sorry to be so 'DOOM & GLOOM' here!

    Since the Propeller ProtoBoards are somewhat inexpensive ($19.99), if it turns out the whole board is fried, then chalk it up to a lesson well learned; Always use a multimeter to verify a unknown power supply before you connect it to something you value.


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    Mike

    Post Edited (Mike Cook) : 3/22/2007 11:40:26 PM GMT
  • HarleyHarley Posts: 997
    edited 2007-03-22 23:26
    Hopefully nothing is 'fried'.

    Maybe it was the ac adapter, heavily loaded by the load, that was buzzing on the table/workbench.

    However, looking at the ProtoBoard schematic, that first 10 µF cap may be 'toasted'.

    Lessons learned can be costly. Hoping not.

    A series diode would help some on protection. But at the cost of apparent lesser battery life by starting with 0.6 v less in use.

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    h.a.s. designn
  • Jake11611Jake11611 Posts: 47
    edited 2007-03-23 10:47
    I didn't plug in a propclip, I was planning to borrow the USB interface from my propstick, which still has to be put on a board (which will probably be done this weekend). I just measured the voltage coming from the regs with a 9v DC meter plugged in, and everything seems fine, 5.1 volt from one reg, 3.34 from the other. I also finshed soldering the acessory kit onto the board. I think I'll read a bit more carefully from now on...
  • LitefireLitefire Posts: 108
    edited 2007-03-29 20:27
    when i plug in a comparator circuit and some sharp rangefinders (all on the 5V traces on my protoboard) something in the board starts to buzz. i assume that it must be the 5V reg... i'm not using it now, but should i be worried about this and get another power source?

    ~~Brian
  • rokickirokicki Posts: 1,000
    edited 2007-03-29 22:49
    The buzzing is probably a toasted electrolytic. I'd scope the 5V line and the incoming voltage and see if it looks good or not.

    You should also check your current draw (you can do this easily with a multimeter).

    It's quite possible your 5V regulator is broken but yet passing enough current for the 3.3V to work correctly.

    I'd say if something buzzes, something is seriously wrong.

    Replacing the electrolytic is pretty easy but make sure you clean off all the old solder, as you probably won't be using the
    same kind of solder and they might not mix so well. (Also note that Parallax is using a higher temperature solder than
    you might be, so adjust your iron accordingly.)
  • LitefireLitefire Posts: 108
    edited 2007-03-29 23:26
    the board is silent when i unplug the rangefinder and accompanying circuitry, and is still working just fine. i think i'm going to avoid the issue for now and just use a stand-alone 5V regulator. if it's working and silent, i'm assuming all is well... any reason not to think that?

    i haven't had it going with the buzzing for more than 3s total... i hope that's not enough time to cause any damage.

    ~~Brian
  • Dennis FerronDennis Ferron Posts: 480
    edited 2007-03-30 05:54
    A friend of mine puts beefy diodes across the power inputs to all his electronics, rather than in series. The reason to do this is that some circuits cannot tolerate the .6 volt diode drop of putting the diode in series to protect the input, and it is easier to add to existing boards because you don't have to cut any traces to insert the diode. The diode is configured so that it is reverse biased when power is connected with the correct polarity, but will forward bias and appear as a short if the supply is backwards. That way you blow a fuse and not your chips if you reverse bias the supply.

    When I built my suitcase computer, I used this idea and put diodes across the breadboard power rails in key places. So far it has saved me twice from frying things with incorrect power supply polarity.

    Interestingly enough, modern CPU's include so many tiny diodes spread throughout the die (they're used to clamp ringing on inputs, so the CPU can run faster) that the CPU as a whole is almost like a giant high-power diode. One time I tried to diagnose a suspected power supply problem inside a laptop by connecting the 5 volt line from a desktop computer directly to the power pins of the CPU. I accidently pumped 25 amps backwards through the Pentium 2 chip on the laptop when I connected power to it backwards for five seconds. (It was enough to trigger the overcurrent protection on the desktop computer power supply that I was feeding into chip.) When I corrected the polarity, the laptop in fact booted and the CPU was still ok.
  • rokickirokicki Posts: 1,000
    edited 2007-03-30 17:24
    "Kids, don't try this at home!"
  • Graham StablerGraham Stabler Posts: 2,510
    edited 2007-03-30 18:54
    I put a bridge rectifier on the input to my cnc controller box, the terminals are still red and boakc but it works both ways [noparse]:)[/noparse]

    Graham
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2007-03-30 20:10
    When using reverse-biased diodes across the power input, you can also add a resettable polymer fuse between the positive input and the diode. This keeps excess current from flowing in case of a reverse connection. (Once, before polymer fuses became commonplace, I used a small incandescent bulb instead. It had similar PTC characteristics to the fuses, with minimual voltage drop under normal load conditions.)

    -Phil
  • computer guycomputer guy Posts: 1,113
    edited 2007-06-09 10:53
    I read the data sheet from the LM2937 and LM2940 today.
    Parallax sells these for the propeller chip.
    And i found this.
    LM2937 and LM2940 data sheet said...

    Features
    Fully specified for operation over −40°C to +125°C
    Output current in excess of 500 mA (400mA for
    SOT-223 package)
    Output trimmed for 5% tolerance under all operating
    conditions
    Wide output capacitor ESR range, 0.01Ω up to 5Ω
    Internal short circuit and thermal overload protection
    Reverse battery protection
    60V input transient protection
    Mirror image insertion protection

    Thought I would post this for future reference, in case anyone needs it...to ease their mind.

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    If you offer cheap PCB fabrication, perl programming or any other helpful services please email me at.
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