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What would you use for a resistor? — Parallax Forums

What would you use for a resistor?

HumanoidoHumanoido Posts: 5,770
edited 2011-05-24 10:05 in General Discussion
I ran out of resistors today. Got me thinking.
What common item or not-so-common object to use as a substitute resistor?
(just for fun)

Comments

  • LeonLeon Posts: 7,620
    edited 2011-05-20 08:30
    A pencil lead?
  • ercoerco Posts: 20,260
    edited 2011-05-20 08:33
    Pencil lead (graphite). Watch the original movie "The Red Tent" about the airship Italia that crashed at the North pole in 1928. They had to repair their "wireless" with a homemade resistor.
  • Mike GreenMike Green Posts: 23,101
    edited 2011-05-20 08:33
    A lump of coal
  • ElectricAyeElectricAye Posts: 4,561
    edited 2011-05-20 08:50
    Mike Green wrote: »
    A lump of coal

    Does coal really work? I know that not all forms of carbon will conduct electricity.

    I suppose you could try distilled water and add tiny amounts of salt to it.

    Or clip one electrode to your tongue and stick the other up your.... armpit.
  • TtailspinTtailspin Posts: 1,326
    edited 2011-05-20 09:05
    The squishy foam they pack your IC chips on for delivery, that stuff is great fun for experimenting with variable resistance.
    Just mash it between two circuit boards, and voila, a genuine variable resistor... I bet that you allready knew about this stuff, didn't you?

    Oh well, nothing to see in this post, please move along to the next post in this thread.
    Thank you
    -Tommy

    P.S. I still have a lump of coal from christmas, Just be careful, that stuff is Flammable when you make a powder from it.
  • LeonLeon Posts: 7,620
    edited 2011-05-20 09:13
    Many years ago a doctor I knew who specialised in foot problems asked me to help him measure pressure at different points on the sole of the foot. I suggested using conductive foam, and actually tested a piece. It worked quite well. I don't know if he actually tried my suggestion, though.
  • FranklinFranklin Posts: 4,747
    edited 2011-05-20 10:36
    Certain types of wire work. There are wire wound resistors (I used to make and calibrate them in a former job)
  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2011-05-20 10:49
    My index and middle finger. I get a good 175K or so if I lick them first.

    There's always my tonque if I need a lower resistance.
  • wjsteelewjsteele Posts: 697
    edited 2011-05-20 11:50
    Mike Green wrote: »
    A lump of coal

    Oh, I got one of those late last year!!!
  • wjsteelewjsteele Posts: 697
    edited 2011-05-20 11:52
    Leon wrote: »
    A pencil lead?

    Did you know that you can lead a horse to water, but a pencil must be lead?
  • davejamesdavejames Posts: 4,047
    edited 2011-05-20 12:02
    Humanoido wrote: »
    I ran out of resistors today. Got me thinking.
    What common item or not-so-common object to use as a substitute resistor?
    (just for fun)

    Various wattages and sizes of incandescent light bulbs. If inductance doesn't matter too much.
  • UnknownUnknown
    edited 2011-05-20 12:18
    davejames wrote: »
    Various wattages and sizes of incandescent light bulbs. If inductance doesn't matter too much.

    Some of the LEDs that Radio Shack carries have resistors in them. You could use a potentiometer.

    What resistance does a capacitor have?

    I would think that different guage wire might have some kind of resistance on the wattage. Different types of metal may have different resistance. You would have to use a multi-meter on different items to find out.

    Maybe you could double up on the items you already are using and that would drop the current.
  • ercoerco Posts: 20,260
    edited 2011-05-20 12:35
    Lots of DIY shunt resistors out there: http://www.sentex.ca/~mec1995/gadgets/shunts/shunts.html

    http://www.reuk.co.uk/Make-a-Shunt-Resistor.htm
  • Jorge PJorge P Posts: 385
    edited 2011-05-20 21:47
    Be carefull if you use graphite, if you put too many amps through it it will light up and get red hot. try gently clamping one end of about 2 to 3 inches of pencil graphite to a jumper cable + and the other end of the graphite to -, and connect it to a car battery, Viola an emergancy heater or emergancy work light. You will want to stand back a bit cuz I've seen them pop and burn. It all depends on the length. WARNING, keep it away from combustables!!!
  • Heater.Heater. Posts: 21,230
    edited 2011-05-20 21:54
    Take the heating element out of your toaster and measure that.
  • HumanoidoHumanoido Posts: 5,770
    edited 2011-05-21 19:09
    I think some small coins would be suitable resistors with their varying degrees of copper, nickel, brass, steel or aluminum content.

    In the old house fuse boxes, some very electrically naive people would substitute a penny or coin for an actual fuse. There was an education awareness campaign to warn people against doing that, so as not to burn down their house!
  • potatoheadpotatohead Posts: 10,261
    edited 2011-05-21 19:45
    Heh... a light bulb screwed in there worked in a pinch too.
  • Jorge PJorge P Posts: 385
    edited 2011-05-21 19:53
    Humanoido wrote: »
    I think some small coins would be suitable resistors with their varying degrees of copper, nickel, brass, steel or aluminum content.

    In the old house fuse boxes, some very electrically naive people would substitute a penny or coin for an actual fuse. There was an education awareness campaign to warn people against doing that, so as not to burn down their house!

    I remember in first grade, about 29 years ago, the power company came to my school and display what would happen if you did that with a penny.

    and bout the dissimilar metals, I think you all may know already, but I will make a post on how to make a home made battery using pennies, nickles or dimes, a paper towel, and viniger... for those that would like to give it a try. Thanks to Forrest Mimms III's notebooks, I learned this when I was 12.
  • vanmunchvanmunch Posts: 568
    edited 2011-05-22 09:52
    Jorge P wrote: »
    I remember in first grade, about 29 years ago, the power company came to my school and display what would happen if you did that with a penny.

    and bout the dissimilar metals, I think you all may know already, but I will make a post on how to make a home made battery using pennies, nickles or dimes, a paper towel, and viniger... for those that would like to give it a try. Thanks to Forrest Mimms III's notebooks, I learned this when I was 12.

    Cool, sounds interesting. Looking forward to seeing it
  • Jorge PJorge P Posts: 385
    edited 2011-05-22 10:57
    vanmunch wrote: »
    Cool, sounds interesting. Looking forward to seeing it
    http://forums.parallax.com/showthread.php?131814-How-to-Make-homemade-batteries...
  • UnknownUnknown
    edited 2011-05-22 15:42
    Jorge P wrote: »
    I remember in first grade, about 29 years ago, the power company came to my school and display what would happen if you did that with a penny.

    Things have changed because the level of copper isn't the same anymore.
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2011-05-23 00:46
    a hot dog. It has enough nitrites to make it conductive. Depending on where you place your wires, you can adjust the resistance. And it should handle plenty of watts.

    http://www.wonderhowto.com/how-to-cook-hot-dog-with-leds-154557/
  • Jorge PJorge P Posts: 385
    edited 2011-05-23 03:17
    Loopy Byteloose wrote: »
    a hot dog. It has enough nitrites to make it conductive. Depending on where you place your wires, you can adjust the resistance. And it should handle plenty of watts.

    http://www.wonderhowto.com/how-to-cook-hot-dog-with-leds-154557/

    hahahaaa, lmao, that's hilarious. How did you even find that? did you search for LED's or "Hot Dogs"?
  • Jorge PJorge P Posts: 385
    edited 2011-05-24 09:11
    I forgot about this, until just now.

    The black antistatic Styrofoam that Parallax uses to put their static sensitive chips in can be used as a variable resistor/pressure sensor.

    Take 2 small pieces of copper clad board, about the same size as the foam., and solder a wire to each. Make sure the pieces are clean of their protective coating and residue from your finger oils. Then place the foam in betwwen the two copper clad pieces with the copper facing the foam. Apply a multimeter to the wires to measure the resistance.

    Now gently squeeze the two pieces, viola, a variable resistor/pressure sensor.
  • davidsaundersdavidsaunders Posts: 1,559
    edited 2011-05-24 10:05
    I have used Pencil lead, by drawing a very thick very dark line on wood, and lengthening/shorting it until I have the correct value.
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