Power in Flux
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Thread: Noise issue related to Curtis 1238

              
   
   
  1. #21
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    Quote Originally Posted by mpipes View Post
    OK, I will double check that. The chassis is all carbon fiber so it won't conduct very well, but I still used fiberglass or plastic enclosures at the 12V distribution points for safety. The mounting brackets for the controller and charger should have a solid film of a filled structural adhesive isolating them from the chassis but are worth a look.

    How about the motor? It's bolted directly to a carbon fiber mount on the swing arm which technically should be isolated from the main chassis via polyurethane suspension bushings but there's still an aluminum shock/air spring.
    Hi
    just to point out: carbon fiber conducts quite well!!!

    flo

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  3. #22
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    Measuring 50kOhm+ from the case of both the charger and the Curtis, to nearby points on the carbon chassis so looks like there is a path through the mounts. Easy enough to fix with a reciprocating saw.

    Quote Originally Posted by flo View Post
    Hi
    just to point out: carbon fiber conducts quite well!!!

    flo
    carbon fiber does conduct but I wouldnt say quite well, or at least maybe not reliably/consistently enough depending what the intent is. Measuring resistance of a raw 12k fiber bundle I get 25ohms over a 6" length.
    Mike Pipes
    - Currently under analysis paralysis.

  4. #23
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    Well - guite well might be misleading.
    But with some rc-plane designs we regulary ran into trouble with twitching servos because the steal linkages (touching the wings) would transfere the impuls from one to another..
    and that is on about 5-8 volts depending on tech at the time...
    Also cf planes regulary burst into fire when accidentally hitting a land line while wooden or glass-fiber planes simply get torn appart

    greets

    flo

  5. #24
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    Still sorting through things here. So far have swapped out a 2-pole relay for a 3-pole relay on the AC Mains input power for the Thunderstruck charger so I can completely isolate it (and its ground) from the system while it's not being used. The BMS and EVCC charge controller work together to control that relay for both dedicated charge state and emergency shut-off.

    Also made some isolating spacers to insert into the holes in the mounting brackets for both the Curtis and the T/S Charger, to separate the device chassis and mounting bolts from the carbon mounts. Havent had a chance to get them installed yet.
    Mike Pipes
    - Currently under analysis paralysis.

  6. #25
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    Isolating the casing of the charger isn't going to fix anything is the charger isn't plugged in.

    ...I had a far longer post than this almost written but as I was finishing it something occurred to me.
    Are you using appropriate logic fixing resistors at the inputs to your power loads in the absence of a control signal?

    In other words have you a pull-down resistor on the Anode of those brake LED's so that the pin isn't simply left floating when the relay is disengaged?
    ...or are you using double throw relays to avoid leaving the pin float?

    If you aren't then any passing cat could dimly light up your parking lights on account of the fact that the LED will present an infinite impedance on that line up to the point of reaching the linear component of it's IV characteristic curve.


    Now the fibrillating relays are a bit more of a mystery - those are power components and not nearly a susceptible to direct excitation in such a fashion, but if they're switched by signal amplifying circuits then those could be. That being said, it's far more likely that there's a power line stability issue where they're concerned. Certainly the dust issue mentioned could cause that. Have you access to an oscilloscope that you can take a proper look at the integrity of the rails?

  7. #26
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    Quote Originally Posted by Spoonman View Post
    Are you using appropriate logic fixing resistors at the inputs to your power loads in the absence of a control signal?
    The lights are controlled by a commercially available LED module manufactured by Penta-Star. The inputs are 12V normally tapped directly from switched lighting circuits, and they also provide the main power for the module. There is no constant power to the unit so in absence of a signal, the unit is powered off.

    Currently, there is no 12V source attached to the system at all while I'm testing and isolating issues, but I can measure 20mV on the 12V power bus when the Curtis motor control is powered on, so it makes sense that that weak voltage is causing the input to float. That voltage shouldnt be there at all though, and while dim lights arent a big deal, the future audio system picking up any noise is.

    I now have the isolating mounts installed at both the Curtis and charger cases to ensure they are not coupled together through the carbon fiber chassis, and the 3-pole relay on the AC Mains input to the charger is also setup so it breaks the ground to the 12V bus while the dedicated Charge Mode is inactive. I did this because the charger internals ground the case and the 96V side together but there's no point having it connected to the system while it's not needed.

    The lights are much much dimmer now after doing this so I'm getting somewhere, but still have some other ground loops to take care of.
    Mike Pipes
    - Currently under analysis paralysis.

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  9. #27
    Senior Member Stevo's Avatar
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    That voltage shouldnt be there at all though, and while dim lights arent a big deal, the future audio system picking up any noise is.
    Maybe if you wire a filter into the audio circuit input, there wont be any issues with noise. Audio is an awesome idea ... it's got me thinking!!!...
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: WORX.VOR.v3.2

  10. #28
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    Progress. Snooped inside the headlight housings (metal) and saw that the park/turn lamp socket assembly is screwed directly to the housing and has the ground wire attached at one of the screws. Simple fix there with relocating the socket mount into a plastic case and running the ground into it instead of the metal housing. Looks like it's a similar situation inside the rear tail lights, those are tougher to get access to so I havent torn into it yet. I also bumped the drive pulley while navigating around the shop and noticed that the brightness of the tail lights fluctuated. Looks like I get to isolate the traction motor from the chassis now too.
    Mike Pipes
    - Currently under analysis paralysis.

  11. #29
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    OK.. so far here's all the ground loops I've been able to isolate. I still have a weak one back at the drive motor even though I put isolating washers/sleeves at the bolts on the motor face. I either broke a sleeve while installing (tight tolerance) or part of the motor can or even part of the terminals are rubbing somewhere at the mount. Havent looked that closely at it yet. However, the lights are no longer powering on when the controller is powered so moving the right direction. I am still measuring about 400mV being induced at the 12volt bus though. Today I cut a section out of the structural core support for the dashboard because it's also all carbon fiber, and is where the audio system head unit and Andromeda display are mounted (thus grounded to the carbon). I grafted that back together with fiberglass. Tomorrow morning that work should be cured and I can start re-connecting all the systems to see if the arduino is still getting any interference.

    path1196.jpg
    Mike Pipes
    - Currently under analysis paralysis.

  12. #30
    Senior Member Stevo's Avatar
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    #$@%& pesky gremlins!
    Last edited by Stevo; 2 Weeks Ago at 1203.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: WORX.VOR.v3.2

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