Electronic PROMposal

Discussion in 'The Projects Forum' started by highschool boy, Jun 9, 2013.

  1. highschool boy

    Thread Starter New Member

    Jun 9, 2013
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    I want to ask my prom date in a really special way. I plan on arranging lightbulbs on an old barn wall in the shape of the word "PROM?" I am using 42 60w bulbs. I want the all to activate on one switch (a pressure plate). I need to know what size battery to use and if it is possible to have these all connected to the same switch. Please help!
     
  2. wayneh

    Expert

    Sep 9, 2010
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    That's an ambitious project. How much time do you have left?

    All those bulbs will require 2,520 watts. That's more than a normal household 15 amp circuit breaker can handle. Even a 20A circuit won't handle it, assuming you have 120V AC mains.

    You asked about a battery. What voltage are these bulbs meant for? If they require 120V for normal brightness, you'd need to supply this voltage with several large batteries in series, for example ten 12V car batteries. Because of the large current - each bulb needs 1/2 amp at 120V - the total current will be 21 amps. That's a big battery, even if the lights only need to be on a few minutes (right?).

    If you could live with LEDs, everything gets much easier because they use so much less power.
     
  3. highschool boy

    Thread Starter New Member

    Jun 9, 2013
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    This is planning for next years prom, so its a whole year away. Will I be able to buy LED's big enough to have the same general effect? Also the barns in the middle if the forest so there is no existing household electricity. I was planning on wiring the whole apparatus to an external battery of some sort?
     
  4. wayneh

    Expert

    Sep 9, 2010
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    Ah, glad to hear it's not a rush job.

    I think LEDs are your only practical solution given the power constraints, unless a portable generator is a possibility. There is a range of commercially available 12V LED lighting, for instance automotive tail lights or architectural strip lighting and such, so I think you will find plenty of options. The challenge will be to find the right brightness while keeping costs down. I know you can already buy LED bulbs to replace typical 60W incandescent bulbs, but they're not cheap!

    I guess a place to start is to determine how much LED power is needed to approximate the look of a 60W incandescent bulb. I think the LED bulbs in the hardware store are under 10W.

    I think strip lighting - maybe even rope lights - could greatly simplify construction of your "sign".
     
  5. highschool boy

    Thread Starter New Member

    Jun 9, 2013
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    Would it be practical to do incandescent bulbs 25W?
     
  6. wayneh

    Expert

    Sep 9, 2010
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    There's no question that reducing the total power, by any means, makes the project easier.

    At 25W time 42 bulbs, that's 1,050W total. That means you could use a 1500W inverter such as this or this (just an example, not a recommendation) and a car battery. The amp draw on the battery won't allow it to last for hours and hours, but long enough.
     
  7. highschool boy

    Thread Starter New Member

    Jun 9, 2013
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    Is there any way to accomplish this project using only car batteries if I were to use LED lights? I would only need it to power the lights for at most 5 minutes so would it drain my batteries?
     
  8. Metalmann

    Active Member

    Dec 8, 2012
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  9. wayneh

    Expert

    Sep 9, 2010
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    Yes, I don't think you'd have any problem making an impressive display to run off a car battery, with no inverter or anything, using LEDs. The energy in a battery is enough to make a LOT of light using LEDs, and the 12V DC of a car battery is well matched to what many of the LEDs require.

    It just comes down to finding the right color, brightness, wiring requirements (sockets versus soldering, etc.) and so on. But you have time, so I think you'll find something you're very happy with. Take a look at what "12V LED" brings up in a Google search and you'll see the huge range of things available. If you want to look into LEDs, look at the manufacturers such as Cree and the big distributors such as Mouser, Newark and Digi-Key. Are you in the U.S.?

    LEDs last a long time, so some of your thinking might be about what they can be used for in the future, after prom. Art? House lighting? Computer or car decoration? Landscape lighting? LEDs are popping up everywhere.
     
  10. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Strings of xmas lights. Cheap, ready made, and all you have to do is bend them into the right shape and nail them in the barn. (The lights, not the prom girls). ;)
     
  11. wayneh

    Expert

    Sep 9, 2010
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    Well done, RB! Best laugh here in a while.

    But seriously, using LEDs opens up all sorts of possibilities. Color shifts, chasers, flashing, and so on.
     
  12. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    What brightness do you need? Or, a better question would be, how far away will you be? I assume you will be in total darkness because there is no electricity available.

    PS, nice RB! Thanks!
     
  13. strantor

    AAC Fanatic!

    Oct 3, 2010
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    Lets not get distracted with all the usual nerdy stuff, circuits and such, and ignore the elephant in the room...

    @highschool boy - This type of display has not worked well for the guys I know that have tried it. I have one friend that makes the same mistake repeatedly, since high school. When he starts to fall for a girl he goes into overkill mode. He tries to be romantic like they show in chick-flicks. Once he scattered hand-cut pink and red paper hearts (thousands, he cut them over a period of days) over a girl's bed on valentine's day after her sister let him in the house. He had a real chance with this girl before that; she actually liked him. When she got home and saw the hearts, she just thought he was a psycho. Girls watch that stuff in movies and get all warm-hearted about it and wonder why no guy ever does that stuff, but when a guy actually does, they return the favor with suspicion and avoidance.

    Maybe others will disagree, but I say, if you really want to get the girl, don't make it creepy for her. Just ask her, with the confidence that you already know she'll say yes. And whatever you do, don't start planning a stunt like this a whole year in advance. You'll build up the event in your mind to the point that it doesn't even feel real anymore, and then when the moment comes and things don't go exactly the way you imagined for months on end, it will be a huge disappointment.
     
  14. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    I think the word PROM? On the side of a barn is much less creepy than signs of love on a girls bed.

    I also think that planning a year in advance is a bit overkill for a highschool girlfriend since things normally change during the highschool years (unless you are competing for a "most unusual invitation" prize and you plan this to be a generic invite for whomever you decide to invite next spring. )
     
  15. wayneh

    Expert

    Sep 9, 2010
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    Strantor raises some good points. A series of smaller gestures in advance would be a lot easier to pull off and far more effective, IMHO.

    It's inevitable to endure some disappointment in life, but strantor raise's a good point about avoiding the obvious setups for a whopper of a big one.

    With the wisdom of advanced age, one of the rules of popping big questions is that you should never ask an important question you don't already know the answer to. Think of lawyers in the courtroom. I think the O.J. glove incident is one of the worst flubs ever, caused by not really knowing in advance how it would go.

    It's not normal to have such confidence in the Prom? answer a full year out. By then it may be another girl or no girl at all.
     
  16. dthx

    Member

    May 2, 2013
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    Look at this RB...and dont let me give this young man the wrong information....
    Here is what I would do....ASk your Physics or Science teacher to look over your shoulder on this one so you dont screw up and burn the barn down or something......
    Make sure that he or she can keep a secret...!!
    RB's got the ticket on this one....
    Get a string or two of 120VAC christmas lights in the color you want....there's like 80 of then in a string....
    Last time I remember they were like.....$1.99 per string at Walmart or the dollar store...you know what I mean...
    Then get an inverter...that's an electronic gadget that converts DC to AC (which the lights use) ....a battery is DC, of course..
    The inverter may plug into your cigaretet lighter or powerplug in the dash of your car or truck..they have those to power a computer while in the car...
    You prob can find someone that has one...and borrow it...
    OR....you can look around on Ebay for one....Ive seen some as cheap as $10.00.
    You can then use a separate car battery hidden somewhere or use your own vehicle...
    Im not so keen on the pressure plate idea....you want to be sure to step on the DC side and not the AC side of the Circuit...
    I think Im right on that....
    Someone here will be glad to draw you a circuit and post it on the site...
    Good Luck...
    D.
     
  17. wayneh

    Expert

    Sep 9, 2010
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    You may have confused this with another thread. Your's is the first mention here of a pressure switch.

    I think the OP has a lot of thinking to do about the specifics of his design before we can help much more. There are many commercial solutions - some already mentioned - that could make a nice display without too much trouble.
     
  18. dthx

    Member

    May 2, 2013
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    Young man....(highschoolboy)....let me give you some advice.
    Now,.. advice is worth what you pay for it and this is free....so keep that in mind..
    This is an electronic forum and the section you are in is "Projects"...
    So...Im breaking the rules to do say this in this part of the forum...
    I have sailed over 10,00 miles in various sailboats and such...to many destinations...and I can tell you that the only time I felt really alive was when I lived on shoestring..on the edge as it were...no money in my jeans....not knowing what's coming next....bartering for food or doing some odd job for dockage...etc..
    If I had done that with plenty of money..where would the adventure be...? ....
    Youre familiar with the words..."carpe diem" Im sure....
    I dont want to start an argument with my compadres...but..
    Do not listen to the naysayers ...
    Not knowing whether she'll say yes or not is the adventure...
    Dive in....it wont kill ya....
    You will remember this project for your entire life....
    Just think....what if she does say yes...?.....Awesome...!
    D.
     
  19. Georacer

    Moderator

    Nov 25, 2009
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    First post - in the parentheses.
     
  20. wayneh

    Expert

    Sep 9, 2010
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    Son of a gun, I must've looked straight past it 3 times. :eek:
     
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