1. Post #681
    Gold Member
    chipset's Avatar
    November 2010
    2,253 Posts


    Made an MDF base plate for my rasp pi.

    MDF is a surprisingly pleasant material to work with, it behaves more like a plastic or a very soft metal than wood. I even find myself using a scribe to mark it rather than a pencil more often than not.
    I had some of this 6mm thick stuff left over after a shelf project and figured I'd make something simple just to keep it off the bench. The screws are regular machine screws so I had to sink the heads into the material to get a flat bottom.
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  2. Post #682
    Hearts
    Agent766's Avatar
    July 2007
    3,041 Posts
    Can a Raspberry Pi do basic vision processing? I want to make a device that uses a webcam to sync my car's blinker with the person's in front of me.
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  3. Post #683
    Gold Member
    LoneWolf_Recon's Avatar
    May 2011
    5,350 Posts
    Can a Raspberry Pi do basic vision processing? I want to make a device that uses a webcam to sync my car's blinker with the person's in front of me.
    You're in luck actually, they recently released the community supported camera module along with OpenCV: http://thinkrpi.wordpress.com/2013/0...era-board-csi/
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  4. Post #684
    Gold Member
    Van-man's Avatar
    August 2009
    19,922 Posts
    Can a Raspberry Pi do basic vision processing? I want to make a device that uses a webcam to sync my car's blinker with the person's in front of me.
    that's some scary level of OCD
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  5. Post #685
    Hearts
    Agent766's Avatar
    July 2007
    3,041 Posts


    I shall call it the Blinker Syncer.
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  6. Post #686
    Gold Member
    chipset's Avatar
    November 2010
    2,253 Posts


    Just made it.
    Share your wire spool storage!
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  7. Post #687
    Gold Member
    Chryseus's Avatar
    February 2009
    3,402 Posts
    Just made it.
    Share your wire spool storage!
    That's a pretty neat idea.
    Would be good if you wind lots of coils and stuff.
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  8. Post #688
    My Scriptz
    nuttyboffin's Avatar
    December 2009
    1,820 Posts
    Yeh, im thinking of doing somthing like this for my room, once the walls exist and the benches are in ect

    Planning on building a coil winding system into it because i plan to do alot of teslacoils / transformers ^^
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  9. Post #689
    Gold Member
    pentium's Avatar
    January 2008
    11,541 Posts
    I need spools so I can then be persuaded to strip down and wind up the 50 conductors that make up the telephone trunk cable I've been slowly chipping away at.
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  10. Post #690
    My Scriptz
    nuttyboffin's Avatar
    December 2009
    1,820 Posts
    I need spools so I can then be persuaded to strip down and wind up the 50 conductors that make up the telephone trunk cable I've been slowly chipping away at.
    That is often the cheapest method of getting wire, buying large multi core cable, irritating as hell however...
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  11. Post #691
    Chezburger's Avatar
    February 2009
    604 Posts
    So, I dug up this 5 watt fm transmitter I have, and tested it. The thing is, it doesn't emit a carrier on one frequency, however, it fucks up the whole 3meter band to noise, I can't hear any other radiostation any more when I turn this thing on, and I have absolutely no clue what's wrong with it.

    Ideas?
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  12. Post #692
    Gold Member
    Chryseus's Avatar
    February 2009
    3,402 Posts
    So, I dug up this 5 watt fm transmitter I have, and tested it. The thing is, it doesn't emit a carrier on one frequency, however, it fucks up the whole 3meter band to noise, I can't hear any other radiostation any more when I turn this thing on, and I have absolutely no clue what's wrong with it.

    Ideas?
    It sounds like it's broken, open her up and post pictures.
    If it's a discrete transmitter it should be fairly easy to fix.
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  13. Post #693
    Gold Member
    pentium's Avatar
    January 2008
    11,541 Posts
    That is often the cheapest method of getting wire, buying large multi core cable, irritating as hell however...
    Hobos can get you the best deals. Just don't ask where they got it from.
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  14. Post #694
    Gold Member
    Dr Magnusson's Avatar
    July 2008
    2,848 Posts
    Just reporting back to say that the installation of the replacement capacitors in my monitor went swimmingly and I am currently using it as my primary monitor, It's like a brand new monitor for a fraction of the price of buying a new one.

    I can see how you guys can get addicted to this stuff!
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  15. Post #695
    🚑 Sarcasm Wambulance 🚑
    SEKCobra's Avatar
    January 2009
    14,956 Posts
    If I short a capacitor it loses its charge, right?
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  16. Post #696
    Gold Member
    ddrl46's Avatar
    October 2007
    3,205 Posts
    If I short a capacitor it loses its charge, right?
    Yes, it can however rebuild some of it's charge after being shorted.
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  17. Post #697
    Hearts
    Agent766's Avatar
    July 2007
    3,041 Posts
    Chryseus, I finally got around to looking at those books you found for me. Thank you very much, it's exactly what I was looking for!
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  18. Post #698
    My Scriptz
    nuttyboffin's Avatar
    December 2009
    1,820 Posts
    Yes, it can however rebuild some of it's charge after being shorted.
    With large capacitors (or any capacitor for good safety practice) you should keep the terminals shorted at all times, i recently got shocked from a bag of 330v caps, i hadnt opened them in a year!
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  19. Post #699
    BuG
    BuG's Avatar
    December 2009
    192 Posts
    With large capacitors (or any capacitor for good safety practice) you should keep the terminals shorted at all times, i recently got shocked from a bag of 330v caps, i hadnt opened them in a year!
    That's impressive, I'd thought that the leakage would discharge them in a much shorter time.

    Edit: Actually I suspect that an electric field has charged it or something, it sounds improbable to me that a cap should have held it's charge for 1+ years.
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  20. Post #700
    Chezburger's Avatar
    February 2009
    604 Posts
    That's some very decent cap then isn't it.
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  21. Post #701
    Gold Member
    Chryseus's Avatar
    February 2009
    3,402 Posts
    Most modern electrolytic caps that are good have a leakage under 1uA, sometimes as low as 100nA.
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  22. Post #702
    My Scriptz
    nuttyboffin's Avatar
    December 2009
    1,820 Posts
    That's impressive, I'd thought that the leakage would discharge them in a much shorter time.

    Edit: Actually I suspect that an electric field has charged it or something, it sounds improbable to me that a cap should have held it's charge for 1+ years.
    The caps i have wernt acctually in a bag, more like a box, cause each of them are about 4700uf xD
    oh, and they were 400v not 330v.

    the big thing you need to watch out for is capacitor memory, where once you dischage them, they regain some of their charge. thats got me a few times, so i always keep the larger ones shorted now.
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  23. Post #703
    Gold Member
    Zero-Point's Avatar
    March 2006
    12,033 Posts
    The caps i have wernt acctually in a bag, more like a box, cause each of them are about 4700uf xD
    oh, and they were 400v not 330v.

    the big thing you need to watch out for is capacitor memory, where once you dischage them, they regain some of their charge. thats got me a few times, so i always keep the larger ones shorted now.
    Speaking of which, I found my box-o-caps the other day... Including the 160,000 uF 40V one I found somewhere.
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  24. Post #704
    Gold Member
    Chryseus's Avatar
    February 2009
    3,402 Posts
    Including the 160,000 uF 40V one I found somewhere.
    Make a spot welder
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  25. Post #705
    BuG
    BuG's Avatar
    December 2009
    192 Posts
    Most modern electrolytic caps that are good have a leakage under 1uA, sometimes as low as 100nA.
    The caps i have wernt acctually in a bag, more like a box, cause each of them are about 4700uf xD
    oh, and they were 400v not 330v.

    the big thing you need to watch out for is capacitor memory, where once you dischage them, they regain some of their charge. thats got me a few times, so i always keep the larger ones shorted now.
    i(t) = C*dv/dt <=>
    i(t)/C = dv/dt

    100nA/4700uF = 0.02128uV/ms

    0.02128uV/ms * 31536000000ms (1 year) = 671.09V.

    So unless I fucked up somewhere, a capacitor with 100nA leakage and 47000 uF capacitance should loose 671V per year due to that leakage. The plot thickens.
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  26. Post #706
    Gold Member
    Tamschi's Avatar
    December 2009
    8,611 Posts
    Is the leakage really a constant current? It should be proportional to the current voltage/charge, making it a differential.

    Edited:

    [sup]U = U_0 * e^(-t/(RC))[/sup] The discharge rating could be for the maximum voltage.
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  27. Post #707
    BuG
    BuG's Avatar
    December 2009
    192 Posts
    Is the leakage really a constant current? It should be proportional to the current voltage/charge, making it a differential.

    Edited:

    [sup]U = U_0 * e^(-t/(RC))[/sup] The discharge rating could be for the maximum voltage.
    You got a point. If we say that the only loss is through the ohmic loss of the dielectric, which I don't think is the case, but if we just say it is, 400V/100nA = 4Gohm's. That gives us an RC time constant of 18800000s or 217,6 days. If you start out at 400V, you could get zapped after 365 days, if we consider >50V as a zap.

    Interesting.
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  28. Post #708
    My Scriptz
    nuttyboffin's Avatar
    December 2009
    1,820 Posts
    Ive always wanted to get hold of some of the big pulsecaps like these:
    http://www.ebay.co.uk/itm/GENERAL-AT...item3383608236

    Probably use them to make a coin shrinker or try and make the worlds most powerful coilgun.
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  29. Post #709
    Gold Member
    Zero-Point's Avatar
    March 2006
    12,033 Posts
    Make a spot welder
    With 40V?
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  30. Post #710
    Gold Member
    Chryseus's Avatar
    February 2009
    3,402 Posts
    160mF is a lot of capacitance, at 40V the total charge stored is 6.4 coulombs, more than enough to be used as a spot welder.
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  31. Post #711
    Gold Member
    Zero-Point's Avatar
    March 2006
    12,033 Posts
    160mF is a lot of capacitance, at 40V the total charge stored is 6.4 coulombs, more than enough to be used as a spot welder.
    Shame I don't really have any use for a spot-welder at this point in time then.
    Also my memory failed me, it's only 78,000 uF. But the capacity is rated -10% + 75%.
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  32. Post #712
    Gold Member
    Falcqn's Avatar
    July 2010
    3,106 Posts
    fuck

    Edited:

    it's so big
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  33. Post #713
    My Scriptz
    nuttyboffin's Avatar
    December 2009
    1,820 Posts

    i got 2 of these on the way, 450v 12000uf
    Charge Q = 5.4 Coulombs
    Energy E = 1215 Joules
    each
    gonna use them as smoothing for my H-Bridge of 600A 1200V IGBT bricks:



    But first... need to find a heatsink large enough for them + 4 100A diodes XD

    Edited:

    Shame I don't really have any use for a spot-welder at this point in time then.
    Also my memory failed me, it's only 78,000 uF. But the capacity is rated -10% + 75%.
    That is the worst tolerance i have ever seen on a actual product....
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  34. Post #714
    Gold Member
    Zero-Point's Avatar
    March 2006
    12,033 Posts

    i got 2 of these on the way, 450v 12000uf
    Charge Q = 5.4 Coulombs
    Energy E = 1215 Joules
    each
    gonna use them as smoothing for my H-Bridge of 600A 1200V IGBT bricks:



    But first... need to find a heatsink large enough for them + 4 100A diodes XD

    Edited:



    That is the worst tolerance i have ever seen on a actual product....
    Strange, mine's a lower capacity and voltage but appears larger. Must be because it's so old.
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  35. Post #715
    My Scriptz
    nuttyboffin's Avatar
    December 2009
    1,820 Posts
    its probibly because it needs much more for its capacitance, voltage only means really it needs a higher dialectric.
    i think.... xD
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  36. Post #716
    BuG
    BuG's Avatar
    December 2009
    192 Posts

    i got 2 of these on the way, 450v 12000uf
    Charge Q = 5.4 Coulombs
    Energy E = 1215 Joules
    each
    gonna use them as smoothing for my H-Bridge of 600A 1200V IGBT bricks:



    But first... need to find a heatsink large enough for them + 4 100A diodes XD

    Edited:



    That is the worst tolerance i have ever seen on a actual product....
    Jesus christ, what are you building? A motor controller for a train?
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  37. Post #717
    My Scriptz
    nuttyboffin's Avatar
    December 2009
    1,820 Posts
    im either gonna use it for a GIANT teslacoil OR most likely a Inverter for a 10Kw+ Ferrite transformer
    to give me like 10Kv out @ 1A then use a doubler or trippler to get 20Kv or 30Kv

    not sure why.... Oh Well! il figure out what to do with it later...

    Edited: Spelling Mistakes.
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  38. Post #718
    Gold Member
    pentium's Avatar
    January 2008
    11,541 Posts
    I don't know what to use this for besides killing people.

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  39. Post #719
    Gold Member
    LoneWolf_Recon's Avatar
    May 2011
    5,350 Posts
    Well it seems spot welders have been in the news lately
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  40. Post #720
    My Scriptz
    nuttyboffin's Avatar
    December 2009
    1,820 Posts
    I don't know what to use this for besides killing people.

    cut the wires off for connectors, mabye find some pipe it fits into, then use it as ammo for a spud cannon!
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