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Discussion in 'General Electronics Discussion' started by JFS-Chatt, Jan 7, 2015.

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  1. JFS-Chatt

    JFS-Chatt

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    Jan 7, 2015
    Hi all,

    I'm a middle school science teacher looking to introduce an after-school science club into electronics. I've only just begun diving in myself, but I want to initially have them use Ohm's Law to calculate the amount of resistance needed to light various colored LEDs using regular AA or C/D batteries.

    My question is this: I'm looking for a cheap way to make a "circuit" board...a way for them to connect wires together as they choose. I was thinking that taking a thin wooden board and installing screws in a grid pattern all along the top would give them a way to loosen the screws a little and then and put the wires underneath the head of the screw to hold the wire in place.
    Something similar to this:
    [​IMG]

    Is this an even remotely good idea, or would touching the exposed screws/wires in the circuit be a recipe for electrocution by battery? Thanks in advance.
     
  2. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Working with LED's will require you to use 1 to 3 batteries depending on the color you want to light.
    Even with 3 AA batteries, the exposed wiring will only be a hazard if the student shorts the battery, the wire could get hot and cause a burn.
    The voltage is low enough that you need not worry about electrocution. The students could lick the wires and receive a ticklish to painful sensation on the tongue, but that is about all.
    As far as your idea is concerned. Panhead screws, and perhaps a washer will allow the students to stick in two or more wires and tighten the screw to make a connection.
    Otherwise you could invest in breadboards. (simply stick the parts in the holes and be done with it.)

    What is the target age group for the students?
     
    KrisBlueNZ likes this.
  3. davenn

    davenn Moderator

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    Sep 5, 2009
    if its just for an electronics club, yeah I would see of the school would invest in a couple of proper breadboards

    like this.....

    ldtut-breadboard.jpg


    here is a pic showing Gryd3's screw and washer style idea .....


    thXETUDOU3.jpg


    cheers
    Dave
     
    hevans1944 and Gryd3 like this.
  4. Gryd3

    Gryd3

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    Jun 25, 2014
    The breadboards dont need to be full size either.. They could be half size, and cost anywhere from $2 - $5 depending on where you buy em.
    They would not require any tools to assemble... stops kids from loosing screwdrivers... or stabbing things with them

    You should probably expect to loose a large number of LEDs as well... Kids enjoy watching them change color and start to smoke when you apply too much power. (ie... the green ones fade to yellow and red before going dark and letting smoke out)
     
  5. JFS-Chatt

    JFS-Chatt

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    Jan 7, 2015
    Awesome info, thanks to all. We don't have any $ as a group, but is sounds like I can buy breadboards out of pocket easily. These are 6-8th graders that have zero circuit experience. Once they get comfortable with adding battery voltages, etc. to light a more forgiving flashlight incandescent bulb I plan to have them devise a plan to light an LED given the current/voltage parameters. I'm learning that you can get tons of LEDs cheaply online so I'll probably just buy a huge pack of them...I only have about 10!

    Any good vendors for low cost breadboards? (I know, I know...Google and eBay away...........)
     
  6. hevans1944

    hevans1944 Hop - AC8NS

    4,606
    2,151
    Jun 21, 2012
    Also keep in mind that the wire size used on commercial solder-less breadboards is limited in size to 22 to 24 AWG solid, not stranded wire. This is typically the size of the wire leads on1/4-watt resistors and small LEDs. If you try to force larger diameter wires into the breadboard it will damage the spring contacts.

    You can "tin" the ends of stranded 24 gauge hook-up wire to get it to fit in the holes without splaying, but that is a real PITA. Buy a few spools (in various colors) of solid 22 or 24 gauge hook-up wire. You can also purchase breadboard jumper wire kits that have a machined pin on each end of the jumper wire. These will last a lot longer in a school environment. These manufactured jumpers are also sold with a matching socket "piggy backed" on the male pin, which allows point-to-point wiring without using up additional breadboard holes, of which there are typically only five per node. See this web site for more information.
     
    KrisBlueNZ and Gryd3 like this.
  7. Gryd3

    Gryd3

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    Jun 25, 2014
    Haha, pretty much.
    Google, eBay.. and if you don't mine the excessive wait, I use DX. It takes about a month, and the quality is somewhat lacking for the cheaper items, but I'm not going to be worried if 1 of my high power LEDs are dead on arrival considering they cost a fraction of my previous supplier.

    Breadboard
    LEDs:
    Assorted, Red, Green
    9V Battery Snap (Or you can get Battery Holders at a slightly higher cost)

    Resistors (Remember you can add resistors together in parallel or series to make a new resistor that has a higher or lower resistance!)
    Assorted, 200K

    The 200K resistors could be used in pairs to form 100K or 400K resistors, or you could use three and get 66K, 300K, or 600K.

    I guess I kinda spammed a few links. but they are cheap... Remember you get what you pay for though. I would no be surprised if a couple holes on the breadboards were too loose for example... Which ever route you go, check for comments and reviews!
     
  8. JFS-Chatt

    JFS-Chatt

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    0
    Jan 7, 2015
    Great stuff. Thanks. Can't wait to get this going!
     
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