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Ebay deals aren't always good — Parallax Forums

Ebay deals aren't always good

TorTor Posts: 2,010
edited 2018-01-17 09:29 in General Discussion
So, here we have a magic item: https://www.ebay.com/itm/112055835359
A strap-less antistatic wristband. A deal I don't recommend, even for $0.99.

Comments

  • Cluso99Cluso99 Posts: 18,069
    Fantastic! Good April Fools joke ;)
  • Heater.Heater. Posts: 21,230
    Ha!

    I guess if the static build up is high enough at some point the discharge is wireless !

  • Tor wrote: »
    A strap-less antistatic wristband
    The first engineer I worked with had a sign hanging in his office.
    This item brings that sign to mind:
    In this office we obey the laws of physics! :smile:
  • I remember seeing this on EEVBlog, it had a 1 meg resistor inside between the contact plate and the screw.

    My favorite example of an expensive resistor is linked below. I wonder if bolting a few of these to your body would make a measurable difference.

    https://m.aircraftspruce.com/catalog/elpages/staticdischargers.php
  • I suppose if the wristband contained a lump of highly radioactive material, then it might ionize the surrounding air and allow for a faster discharge. I wouldn't want to wear it though, if it did.
  • ceptimus wrote: »
    I suppose if the wristband contained a lump of highly radioactive material, then it might ionize the surrounding air and allow for a faster discharge. I wouldn't want to wear it though, if it did.

    Polonium is used in anti-static brushes because it emits positively charged particles (mostly alpha particles). They're supposed to be safe as long as you don't eat it.
  • ercoerco Posts: 20,256
    edited 2018-01-19 18:47
    Unit price is cheaper in this 5-pack. Surely wearing all 5 straps on your wrist (or linked as a belt or suspenders) brings extra ESD protection. Provides lots of other types of protection too, since women will want nothing to do with a man wearing such a belt or suspenders.

    https://www.ebay.com/itm/5pcs-Cordless-Wireless-Anti-Static-ESD-Discharge-Cable-Band-Wrist-Strap-Slim/371740776858
  • Where was I when this amazing technological breakthrough was discovered? @ .99 it's a steal, I'm going to buy them out and flip them for a fortune.
  • signal sent to ground via bluetooth....
  • xanadu wrote: »
    My favorite example of an expensive resistor is linked below. I wonder if bolting a few of these to your body would make a measurable difference.

    https://m.aircraftspruce.com/catalog/elpages/staticdischargers.php

    Really? These are essential to change the electrical shape of the aircraft - in fact, to the point that for a commercial aircraft, it won't be allowed to fly if more than two are missing. Without them, HF comms are affected.

    I used to have a couple of carbon-fibre static-dischargers in my desk drawer. They had been on a very large commercial aircraft for several years and were as sharp as a needle, having lost material a few electrons at a time.

    They are not like the rubber conductors or lengths of chains people hang from the bumpers of cars - they really help to discharge the static that builds-up when a metal object passes through air at high speed.
  • Heater.Heater. Posts: 21,230
    Hugh,
    I wonder if bolting a few of these to your body would make a measurable difference.
    Actually it may very well do that.

    Electric charge loves to jump off the most pointy parts of whatever object it is on.

    Even if that means just jumping off into the atmosphere.

    Don't they teach this simple physics in school anymore ?

  • xanaduxanadu Posts: 3,347
    edited 2018-01-20 06:30
    @Hugh

    Really. I have some too. The acceptable number probably is on a CDL and varies by aircraft, unless you know of a FAR you'd like to share. I find the grounding straps going bad a lot quicker than the wicks.

    @Heater

    If it were taught in high school I wouldn't remember. In flight school they taught us static will try to discharge from antennas because they're pointy. Dischargers are both pointy and have a lower corona voltage. I mentioned "measurable" because I think it would bleed off some static but probably not as fast as one could build it up, or discharge it into whatever they touch.

    Composite aircraft are a little scary in this regard. There's a famous story about a glider getting struck by lighting and exploding. They ended up jumping out and pulling chutes.

    Maybe I should mailbag some to EEVBlog he has all the test equipment.
  • Heater.Heater. Posts: 21,230
    If you were taught this in school you certainly would remember. A nice big Van de Graff Generator that you can draw 6 inch sparks off is not easily forgotten. Not to mention standing girls on plastic buckets, charging them up and watching their hair stand on end.



    Or what about a Wimshurst Machine?



    The glider story is amazing. Back in 1990 something a guy I was working with a glider pilot. He took us up for a spin. A winch launch is pretty dramatic. No parachutes anywhere!



  • xanadu wrote: »
    @Hugh

    Really. I have some too. The acceptable number probably is on a CDL and varies by aircraft, unless you know of a FAR you'd like to share. I find the grounding straps going bad a lot quicker than the wicks.

    I had an argument with [a certain aircraft manufacturer] about their 'ten fitted: ten required' requirement in the MMEL/CDL. I seem to remember the (grudging) result being that the aircraft could depart if one was U/S.
  • I buy at Ebay all the time and only had one bad item. But the seller did give me a full refund. You just have to know what your buying what looks good and what doesn't. Ebay has saved me a ton of cash!!!
  • @hugh

    Sounds like the short version of 'it depends'. It it were more than 1 they would need to break it down by the surface it were attached to. Missing 2 on one surface is surely worse than missing 1 on two surfaces. I think.
  • Heater.Heater. Posts: 21,230
    Just ordered mine. Can't wait for it to arrive. :)
  • Heater.Heater. Posts: 21,230
    Just ordered mine. Can't wait for it to arrive. :)
  • Cluso99Cluso99 Posts: 18,069
    I wasn't happy with mine, so I have asked for a refund ;)
  • Cluso99 wrote: »
    I wasn't happy with mine, so I have asked for a refund ;)

    Are they going to charge you return shipping?
  • Cluso99Cluso99 Posts: 18,069
    Cluso99 wrote: »
    I wasn't happy with mine, so I have asked for a refund ;)

    Are they going to charge you return shipping?
    Yes. Minimum from here is ~$3.00. Not bad for a $1.00 shipping fee ;)
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