Ice-Hockey Skate Customization

Discussion in 'The Projects Forum' started by MasonLynch94, Dec 11, 2012.

  1. MasonLynch94

    Thread Starter New Member

    Dec 11, 2012
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    Hello, :confused:

    I have been Ice Skating for several months (8) and have had a idea to customize My Skates, I started by drilling a hole in the footbed and put LED's on the bottom of the skates with a two wires going into the boot itself. They went off to a switch and an old phone battery, these were all small enough to fit in the skate (Keeping it tidy) without disrupting my foot or my skating ability.

    So what I now need is a Battery Slim enough to fit into my skates with some sort of clip terminals or a battery holder cheap and affordable.

    I don't know the power needed to make the LED's operate with full brightness? any Solutions to this and my Idea above?

    Can I get a resistor and use a 9V Battery with a basic Snap connector?

    Thank, M.Lynch
     
  2. wayneh

    Expert

    Sep 9, 2010
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    You can, but there may be better choices. Phone or iPod batteries will be smaller and have a higher power density, so more light between recharges, with less volume in your boot.

    A "normal" LED needs at least about 3V (the exact minimum depends on the color) and about 10mA to be nice and bright. They will tolerate 20mA and may briefly survive 30mA but that level will shorten their life. With a 9V supply, you could put two LEDs in series and then use a resistor to limit the current. Using just one LED with a larger resistor will also work, but will use just as much power as 2 in series and make half as much light. Any battery less than about 7V will not light more than one LED in series (unless you are using only red LEDs, which have the lowest voltage drop).

    A battery giving less than about 4V requires a voltage boost circuit to light an LED. That's how those solar landscape lights work with a single AA or AAA cell.
     
  3. MasonLynch94

    Thread Starter New Member

    Dec 11, 2012
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    I have 3 LED's (Blue on 1 Skate and the same on the Other) do you know what kind of power they will need?

    How do I work out what resistor I need?
    I think 9V batteries are easier as they have easy connector tabs and easily replaceable as I cant connect an IPod/IPhone battery easily, i would need to be able to Solder and i can't.

    Thanks
     
  4. wayneh

    Expert

    Sep 9, 2010
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    You may want to find an ankle light that's powered by button cells and adapt it. I use such a thing when running this time of year - when it's dark by 4PM. There are a LOT of similar products available, for instance this and this and this and this and even this.

    My point is, don't reinvent a wheel.
     
  5. MasonLynch94

    Thread Starter New Member

    Dec 11, 2012
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    Thanks, I've looked into these designs before but wont really fit on the bottom of my skate, I looked at the Nite Beams but is US purchase and I cant do that. I found out that the LED's need 6V so if I use a 9V what Size/measurement resistor do i need? Thanks again
     
  6. wayneh

    Expert

    Sep 9, 2010
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    OK, you want to use a 9V and blue LEDs.

    Any chance you might use 4 LEDs instead of just 3? It's a small issue but you could use 2 strings of 2 blue LEDs + 1 resistor each, with the 2 identical strings in parallel. If you use 3 LEDs, you'll still need two strings; one with 2 LEDs + resistor and the other with 1 LED + a different resistor.

    Either way, you need to know about the specifications for your LEDs, particularly the Vf (forward voltage) and the current rating (for example 30mA continuous).

    Suppose the Vf is 3.3V and the maximum current is 20mA or more. I'd shoot for maybe 15mA using a fresh battery at 9V. Your battery will drop to 8V or less fairly quickly, so the LED will see 10-15mA over most of its life and will last a long time. You can consider higher current if you want to squeeze out as much brightness as possible, at the expense of LED life.

    So 9V minus the 6.6V drop across 2 LEDs leaves 2.4V to drop across the resistor at a current of 15mA. Ohms law ∆V = I•R gives the solution: 2.4V = 0.015A • R, and so R = 160Ω. A standard value of 150 or 180Ω would work, and a value of 120Ω would limit current to 20mA which would also be fine if your LED is rated to 25-30mA continuous.

    The same analysis for a single LED gives 5.7V=0.015A•R and R = 380Ω. Standard values are 330 and 390Ω, and both would be fine.

    I should add that you could extend battery life by going down to 5mA or so. The LED will still be bright (not nearly AS bright, but still well lit) and the battery will last much longer. You just use higher ohms resistors.
     
  7. MrChips

    Moderator

    Oct 2, 2009
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  8. MasonLynch94

    Thread Starter New Member

    Dec 11, 2012
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    Thanks I now have the Resistors I need. The Issue with them Powering themselves is room within the Skate and the Mass of them. So you mean using something to collect Kinetic and then use it to power the LED's?
     
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