Shop OBEX P1 Docs P2 Docs Learn Events
how to adjust brown out voltage — Parallax Forums

how to adjust brown out voltage

prozachprozach Posts: 11
edited 2010-03-01 21:54 in General Discussion
Can anyone tell me how to adjust the brownout voltage for the sx28?· I am using an atx power supply that drops to 4v when hit with a static discharge to the chasis.· This in turn is burning up the chip.·

Zach

Comments

  • JonnyMacJonnyMac Posts: 9,211
    edited 2010-02-17 02:39
    You can specify brown-out voltage in the DEVICE line -- like this (from an SX/B program):

    DEVICE          SX28, OSCHS2, BOR42
FREQ            50_000_000


    You can use BOR42, BOR26, BOR22, or nothing (off).

    A bigger question... is your power-supply properly loaded so that it will regulate correctly? My guess is that it's not and is going over-voltage and damaging the chip.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Jon McPhalen
    Hollywood, CA
  • RobotWorkshopRobotWorkshop Posts: 2,307
    edited 2010-02-17 20:39
    It doesn't sound like the brown out setting is your problem The SX28 can run at 3.3V so even if your power supply drops to 4V the SX28 should still run.

    The scary part is "when hit with a static discharge to the chasis" and concerns me that the static charge may be getting to the chip. Does the chip just die or does it actually/physically burn up?? Big difference! If it just dies have you tried using the SX Key to download your program on the off chance that you just lost the code on the chip?

    If your circuit is subject to Static shocks, etc then you have to seriously look at what you're doing. If this was a mobile robot then some leave a beaded pull chain dragging to help dissipate the static charge before one builds up. You'll also want to make sure your power is properly conditioned with filter caps, etc and if you are controlling things with the SX chip that you consider opto isolators and other things to protect the micro controller. My guess is that what your are seeing would probably happen with any controller you use and isn't a problem with the SX28.

    Do you have a schematic or picture of your setup?
  • prozachprozach Posts: 11
    edited 2010-03-01 21:54
    The SX is used in an arcade setting on carpeted floors.· The kids discovered early that a good static charge could add a coin to the game.· That problem has been solved, however the kids now rub there feet on the carpet and try to shock it trying to get a credit.· I believe this is the cause of the failure, but I may be wrong.

    I am using a atx computer power supply to run the game since they are cheap.· The 5v is rated at 30 amps but I only draw a·2-3 at any time.· Possible an overvoltage is the problem.· I do not know how regulated these are at low current.

    The problem only happens maybe one in 1000 plays, so I am having a tough time finding the cause.· I used a car coil to really shock the game and this is when the power supply dropped to about 4v·and caused the chip to burn.· I am unable to reprogram any of the chips and a few have actually burned up.

    The I/O's are current protected but not isolated by an opto.

    Zach
Sign In or Register to comment.