Thursday, December 22, 2011

The Lights Project - A Bulb, A Stable and A Steady Hand



Welcome back to Day#7!

In the last few posts, we've been using the battery-operated STRALA lights - and their Target-dwelling counterparts - to make a variety of playthings:
And we're not done!

But a question came up from a reader: how safe are these lights? 
It's a good question and the short answer is: about as safe as a typical store-bought toy.
In the US, the power supply to our homes is 110 V. In Singapore where I grew up, it was 220 V. That's high. And that's why we buy these child-proof shields to stick in the wall sockets. The circuits in our lights projects are battery-operated, and typically use two batteries (that's just 3V), which is very small. There is always the danger of disgusting leaky batteries, of course, or accidental short circuits, which could get hot enough to give you a nasty surprise on touch. But these could happen with any battery-operated toy from a store, too. And certainly you won't get electrocuted, if that's what you're worried about. So yes, these lights are pretty safe. Besides, I wouldn't be letting my kids (or - when I was a teacher - my students) play with them if they weren't. 

And now, are you ready to try lights-from-scratch? 

Of course you are.

Why, though? 
Why not just stay with strings of lights?
Well, so that you're not limited to using 10 lights at a go, or having them all on or off at the same time.
I mean, sometimes, you might just want ONE little light. 

Today we are going to make two such single-light crafts, using mini light bulbs. Tomorrow, we will be using LEDs, and I'll tell you then how they are different from bulbs. But that's tomorrow's story.

A circuit-from-scratch is easier than you think. But you will need to go shopping.
Circuits-from-scratch have typical components, all of which can be bought from Radioshack or some similar store. Or online -google "electronic components" or something similar. You could also invest in Science-y circuit kits for kids, but that's limiting. We bought one of those Snap Circuit sets at a garage sale for $2 and have had loads of fun with it, but at the end of the day, my girls still can't visualize the layout of a circuit the way they can with from-scratch construction. Plus you can also buy the separate components for much less than in a kit.

First, you need batteries. Everyone knows what those are. What's also useful is a battery-holder, which has leads (the wires leading out of the contraption) for easy connecting to other circuit bits. They come in different sizes, and for different numbers of batteries.

If you don't have them, you can always just tape batteries together with masking tape (or electrician's tape)

and attach your own leads (wires to join to other things), which brings us to -

insulated bell copper wire (which are also available from hardware stores)

That colorful plasticky coating is insulation, meaning it doesn't conduct electricity. For the wires to work, you'll need to strip the ends to expose the conducting copper wire inside.
There are fancy wire-strippers (they look like pliers) you can buy, but you can also use scissors. Make a shallow pinch with the scissor blades in the insulation layer; not deep enough to actually expose the copper wire underneath.

Use your finger nail to deepen the pinch till you do see the copper wire underneath. Then twist and pull off the end bit of insulation. Fingernails are better than scissor blades for this, because they don't accidentally slice through the fine copper wires.

Twist that copper wire bunch (so it doesn't splay out) and make a sort of loop. Make a short two-ended wire and tape this on the ends of the batteries, so that it connects the "-" of one battery to the "+" of the other. 

Tape that down with masking tape so it stays secure.

You've now connected two batteries in series. They work the same way as this,

but, side-by-side, they are more secure and less likely to shift apart, inadvertently disconnect and sabotage your circuit (grrr).


Their other, unconnected ends will need wire leads, so strip and stick more wires to those ends with masking tape.

Now, there are such things as wires that have alligator clips already connected at their ends like these:
They are very convenient, are alligator clips, which is why Science kits are full of them. But bear in mind that they have a high resistance to current, which is a fancy way of saying that if you use them in a circuit, they suck and waste power, and result in annoying things like dimmer light bulbs and softer buzzers and slower motors and so on.

Then there are bulbs:

These are little things that light up (duh). They have something called a filament which gets hot and glows.
If you look at a bulb, it has a voltage and power rating. This one below operates at 2.2V and 0.25 W. The wattage indicates how bright that bulb can be - just like the bulbs you use in your lamps at home. The voltage tells you what sort of battery power you need to get it to be that bright. Our typical cylindrical batteries are 1.5V each, so one battery would be insufficient for this bulb (and would make it exceedingly dim). Two batteries (1.5+1.5 = 3V) are better, although their combined voltage is more than the bulb's 2.2 V. However, with all the extra wires and other circuit elements sucking power away unto themselves, two batteries work out to be just right for a bulb like this.

That bulb above is sitting in a bulb holder, more varieties of which are shown below:

They are useful because they have built-in sticky-out bits that allow easier connecting to wires and stuff. Some bulb holders (like that black one above) even have wire leads already connected.

If you don't have a bulb holder, you can make one yourself from aluminum foil and cardboard. Go here for the Bulb Holder tutorial.

Finally, this is a fun and useful but optional circuit element - a switch.

If you can't buy them, make your own with office supplies and cardboard 

and wind the wire ends around the feet of paper fasteners to make contact.

See here for the Switch Tutorial.

And that brings us to the end of Circuit Components 101. 

On to the projects!


Here is a little nativity scene Emily made out of a box.

I helped her make an indented perch for the angel

and added a single bulb, hiding the circuitry -including a switch - in the attic of the stable.

The layout for this simple one-bulb circuit is the same as this one here.

Not that there were electric lights in Bethlehem in those days, but Emily was thrilled with an illuminated manger scene.

There are a multitude of applications for this one-bulb circuit - or adding more bulbs - you can use it to light up anything: lanterns, dollhouse lamps

flashing robot bodies, alien spaceships (well, OK, technically those are LEDs)


personal reading lamps.... endless possibilities.

Illumination aside, what if we introduce the element of suspense and turn a lighted project into a game? Here is another single-bulb project - a very common Science Fair entry which I call The Steady Hand Game.

The principle here is that if the circuit is complete/closed (i.e. not broken/open), the bulb will light up. The object of the game is to move a loop of wire from one end of a bendy path to the other without touching the bendy wire. Touching the wire closes the circuit and makes the bulb light up. It requires some concentration and a steady hand (hence the name) to do this!

Here it is in action:
video


Here's the how-to:

First, twist an exposed (i.e. not insulated) wire into a loop with a handle. I used regular florist's wire. You can find these in coils or in packs of 12" lengths in the floral section of Michaels or hobby lobby. Buy the plain silver-colored ones, not the fancy colored ones (which have an insulated coating).

Next, bend more of this uninsulated wire into a wiggly shape like this. Make sure it had long ends for mounting on a box. I had to twist two 12" lengths together to make a long enough shape.

Slip the bendy wire through the loop, and poke the two ends into a shoebox.

Under lid, make your circuit:



Put the cover back on, and you're ready to play! Note that our version was extra fancy - it has both a light (top LH corner) and a buzzer (top RH corner). The paperclip switch in the middle allowed us to choose whether we want to be blinded by light or annoyed by sound whenever we made a slip in the game. 


This buzzer, having an incompatible voltage rating, required some circuit-enhancement to make it respond as quickly as the bulb. I wasn't up to getting everyone in the car to go to Radioshack again for more thingamajigs, so we left it as a happy theoretical construct, and played with just the light option.



Tomorrow: Electric Circuits 102 and some traffic lights!

4 comments:

  1. Our idea that great!
    I wish you have much health and happiness in your life.
    May your Christmas Day be harmonious and Joy
    Success in 2012
    hugs

    http://tearpiaocupacional.blogspot.com/

    ReplyDelete
  2. Yay for circuits tutorials! I got Mike Snap Circuits for Christmas and he opened it early (since he's getting wisdom teeth pulled tomorrow, we let him have Christmas a week early and the kids were surprisingly fine with that). He and the kids have been having a blast with it. I'm sure they would love from-scratch circuits like this, too!

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  3. Thank you so much! I came across this by mistake and am so happy to find simple circuits explained with lots of photos and for kids! We'll definitely be doing this.

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  4. thanks was the last day of holiday and i had to do my holiday homework thanks a lot

    ReplyDelete

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