First Science Fair project - HELP!!!

[SJTM]

I know nothing about electricity, but my 7 yr old wants to build an
electric buzzer for his science fair. We followed instructions in a
book from the library but no buzzer. Project seemes straightforward.
Wrap uninsulated wire 200 times around a nail tacked into a board.
Attach one lead to a simple metal bracket that holds the face of a 3
inch piece of hack saw blade about 1/8 inch from the head of the nail.
the other lead goes to a simple switch. The other switch contact runs
to a battery, size unspecified but we used a 6 volt lantern battery.
The other battery lead goes to a paper clip fastened to the based and
bent to just touch a tip to the edge of the other face of the hacksaw
blade.

In theory the electrical current should vibrate the hacksaw blade,
causing it to buzz, appatrently by striking the nail head. In fact,
all we get is some arcing between the hacksaw blade and the paperclip
tipwhen they touch. the paperclip gets very hot. The wire coil on
the nail is coll to the touch.

I also tried two 6v batteries in series but no apparent change. I am
stumped with no idea what to try next, and my son is getting anxious
that he will have no project.

What is the coil of wire supposed to do? Does this have a name - it
looks like a motor winding? We used 24 gage wire - is this the wrong
gage? does it matter? My son did the winding, so it is not perfectly
evenly distributed along the length of the nail. Does this matter?
Did we do too many or too few windings? Total outside diameter of the
winding is probably about 1/2 inch max.

I assume we have a complete circuit or we would not get the arcing.
Please help with any thoughts as the project is due this week.
Thanks.

 

[John Popelish]

SJTM wrote:

I know nothing about electricity, but my 7 yr old wants to build an
electric buzzer for his science fair. We followed instructions in a
book from the library but no buzzer. Project seemes straightforward.
Wrap uninsulated wire 200 times around a nail tacked into a board.
Attach one lead to a simple metal bracket that holds the face of a 3
inch piece of hack saw blade about 1/8 inch from the head of the nail.
the other lead goes to a simple switch. The other switch contact runs
to a battery, size unspecified but we used a 6 volt lantern battery.
The other battery lead goes to a paper clip fastened to the based and
bent to just touch a tip to the edge of the other face of the hacksaw
blade.

In theory the electrical current should vibrate the hacksaw blade,
causing it to buzz, appatrently by striking the nail head. In fact,
all we get is some arcing between the hacksaw blade and the paperclip
tipwhen they touch. the paperclip gets very hot. The wire coil on
the nail is coll to the touch.

I also tried two 6v batteries in series but no apparent change. I am
stumped with no idea what to try next, and my son is getting anxious
that he will have no project.

What is the coil of wire supposed to do? Does this have a name - it
looks like a motor winding? We used 24 gage wire - is this the wrong
gage? does it matter? My son did the winding, so it is not perfectly
evenly distributed along the length of the nail. Does this matter?
Did we do too many or too few windings? Total outside diameter of the
winding is probably about 1/2 inch max.

I assume we have a complete circuit or we would not get the arcing.
Please help with any thoughts as the project is due this week.
Thanks.

You have a complete circuit or there would be no current heating
anything. The idea behind the buzzer is that the hack saw blade forms
part of a switch that is closed and supplies current ot the coil, but
is also attracted to the nail. This attraction opens the switch,
breaking the coil circuit, so that the nail no longer attracts the
blade. But once the blade is not attracted to the nail, it springs
back and closes the switch, repeating the cycle.

Getting a good buzz out of this arrangement involves adjusting the
spring pressure that is closing the contact point against the blade to
something less than the magnetic force the nail can apply to the
blade.

--
John Popelish

 

[Michael Black]

SJTM (stephenmurphy@mindspring.com) writes:

I know nothing about electricity, but my 7 yr old wants to build an
electric buzzer for his science fair. We followed instructions in a
book from the library but no buzzer. Project seemes straightforward.
Wrap uninsulated wire 200 times around a nail tacked into a board.
Attach one lead to a simple metal bracket that holds the face of a 3
inch piece of hack saw blade about 1/8 inch from the head of the nail.
the other lead goes to a simple switch. The other switch contact runs
to a battery, size unspecified but we used a 6 volt lantern battery.
The other battery lead goes to a paper clip fastened to the based and
bent to just touch a tip to the edge of the other face of the hacksaw
blade.

In theory the electrical current should vibrate the hacksaw blade,
causing it to buzz, appatrently by striking the nail head. In fact,
all we get is some arcing between the hacksaw blade and the paperclip
tipwhen they touch. the paperclip gets very hot. The wire coil on
the nail is coll to the touch.

I also tried two 6v batteries in series but no apparent change. I am
stumped with no idea what to try next, and my son is getting anxious
that he will have no project.

What is the coil of wire supposed to do? Does this have a name - it
looks like a motor winding? We used 24 gage wire - is this the wrong
gage? does it matter? My son did the winding, so it is not perfectly
evenly distributed along the length of the nail. Does this matter?
Did we do too many or too few windings? Total outside diameter of the
winding is probably about 1/2 inch max.

I assume we have a complete circuit or we would not get the arcing.
Please help with any thoughts as the project is due this week.
Thanks.

If it gets hot, try a smaller battery, like a D cell or maybe a few
in series (each supply 1.5volts).

The coil becomes an electromagnetic. Just like a natural magent,
it will attract something metal, though it requires that current
through the coil.

A buzzer is just an extension. The electromagnet attracts the
lever, "click" as it strikes. But then there has to be some mechanism
for the power to the electromagnet to be turned off. When the electromagent
is turned off, the lever moves away. This causes that "switch" to
enable power to the electromagnet once again, and the whole thing starts
again. Since the limit is mechanical, this happens at an audio rate,
and that's where the buzzing comes from.

Make sure the hacksaw blade is of a material that is attracted to a magnet;
take a magnet you have lying around and make sure it sticks to the hacksaw
blade.

I guess your paperclip is the switch that turns the buzzer on and off
as the lever moves. Make sure that is working properly, manipulate
things with your finger with the power off to see if it goes from
contact to no contact.

Michael

 

[Jerry G.]

All the other answers you received are very good. But, I noticed something
in your description of the wire. You referred to "un-insulated" wire. The
wire should not have rubber insulation to be the best for your application,
but must be electrically insulated, as like motor or transformer wire. This
wire is enamelled coated, as to not be shorting through every layer and
turn. The ends where the wire is electrically connected have to have the
enamel scraped off, so a conduction can take place.

Try to see if you can get something like AWG # 24, or AWG # 26, or AWG #
28. Anything in that size range should work. In theory, the more turns,
the stronger the field, and the less current it will pull, due to higher DC
resistance. This is also to some limitations.

As for a home made electromagnet, I would start with about a hundred turns
or so, if you can fit that amount on to your core base.

If the DC resistance goes to high, then the magnetic field will start to
also be weakened. But, in your case, you should not have to worry about
that.

If you call around to places that rebuild electric motors, and or
transformers, I am sure that they can sell you the end of a roll. I am sure
that for a few hundred feet, they will not charge very much. If you say it
is for a kid's science fair project, they may even give you the wire. You
can also tell them that if they help you out with the information and parts,
you will promote them by telling everyone where the parts came from. If you
go to Radio Shack, they will probably charge a lot for only a few feet.
Infact, at a place that does motor rebuilds, their tech can probably give
you some good tips.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"SJTM" <stephenmurphy@mindspring.com> wrote in message
news:9bb4ae36.0403211522.678b5d99@posting.google.com...
I know nothing about electricity, but my 7 yr old wants to build an
electric buzzer for his science fair. We followed instructions in a
book from the library but no buzzer. Project seemes straightforward.
Wrap uninsulated wire 200 times around a nail tacked into a board.
Attach one lead to a simple metal bracket that holds the face of a 3
inch piece of hack saw blade about 1/8 inch from the head of the nail.
the other lead goes to a simple switch. The other switch contact runs
to a battery, size unspecified but we used a 6 volt lantern battery.
The other battery lead goes to a paper clip fastened to the based and
bent to just touch a tip to the edge of the other face of the hacksaw
blade.

In theory the electrical current should vibrate the hacksaw blade,
causing it to buzz, appatrently by striking the nail head. In fact,
all we get is some arcing between the hacksaw blade and the paperclip
tipwhen they touch. the paperclip gets very hot. The wire coil on
the nail is coll to the touch.

I also tried two 6v batteries in series but no apparent change. I am
stumped with no idea what to try next, and my son is getting anxious
that he will have no project.

What is the coil of wire supposed to do? Does this have a name - it
looks like a motor winding? We used 24 gage wire - is this the wrong
gage? does it matter? My son did the winding, so it is not perfectly
evenly distributed along the length of the nail. Does this matter?
Did we do too many or too few windings? Total outside diameter of the
winding is probably about 1/2 inch max.

I assume we have a complete circuit or we would not get the arcing.
Please help with any thoughts as the project is due this week.
Thanks.

 

[Michael Black]

"Jerry G." (jerryg50@hotmail.com) writes:

All the other answers you received are very good. But, I noticed something
in your description of the wire. You referred to "un-insulated" wire. The
wire should not have rubber insulation to be the best for your application,
but must be electrically insulated, as like motor or transformer wire. This
wire is enamelled coated, as to not be shorting through every layer and
turn. The ends where the wire is electrically connected have to have the
enamel scraped off, so a conduction can take place.

I didn't catch the "uninsulated bit". If that's the case, no wonder

there are problems. It's an obvious point to us (which is probably why
I did not pay attention), but I think it may be a common mistake for
people trying this level of project. I'm sure it's been mentioned
somewhere as a common mistake when making electromagnets.

Michael

 

[CFoley1064]

Subject: Re: First Science Fair project - HELP!!!
From: "Jerry G." jerryg50@hotmail.com
Date: 3/21/2004 10:28 PM Central Standard Time
Message-id: <c3lq8g$5se$3@news.eusc.inter.net

All the other answers you received are very good. But, I noticed something
in your description of the wire. You referred to "un-insulated" wire. The
wire should not have rubber insulation to be the best for your application,
but must be electrically insulated, as like motor or transformer wire. This
wire is enamelled coated, as to not be shorting through every layer and
turn. The ends where the wire is electrically connected have to have the
enamel scraped off, so a conduction can take place.

Try to see if you can get something like AWG # 24, or AWG # 26, or AWG #
28. Anything in that size range should work. In theory, the more turns,
the stronger the field, and the less current it will pull, due to higher DC
resistance. This is also to some limitations.

<snip>

Home run. The uninsulated business would describe exactly what's going on, and
why your buzzer won't work. If you want a quick fix, try your local radio
shack for

<quote from website>
Radio Shack 278-1345
Magnet Wire Set
Three-spool assortment totaling 315 feet at a value price. This enamel-covered
solid-conductor copper wire is perfect for winding your own coils and
electromagnets. Includes 40 feet of 22-gauge, 75 feet of 26-gauge and 200 feet
of 30-gauge. Priced three to a package.
<eoq>

Call first to make sure they've got it in stock. Start with the 26 AWG (the
middle thickness wire). Use a penknife to carefully strip off all the
insulation on the ends of the wire where you connect it to the battery and
switch.

Good luck, man. Been there, done that, got the tee-shirt. Hope you end up
looking like a genius!

Chris

 

[michael turner]

On Sun, 21 Mar 2004 15:22:54 -0800, SJTM wrote:

I know nothing about electricity, but my 7 yr old wants to build an
electric buzzer for his science fair. We followed instructions in a
book from the library but no buzzer. Project seemes straightforward.
Wrap uninsulated wire 200 times around a nail tacked into a board.
^^^^^^^^^^^

Stop right there!!!

You've got a complete *short-circuit*.

Attach one lead to a simple metal bracket that holds the face of a 3
inch piece of hack saw blade about 1/8 inch from the head of the nail.
the other lead goes to a simple switch. The other switch contact runs
to a battery, size unspecified but we used a 6 volt lantern battery.
The other battery lead goes to a paper clip fastened to the based and
bent to just touch a tip to the edge of the other face of the hacksaw
blade.

In theory the electrical current should vibrate the hacksaw blade,
causing it to buzz, appatrently by striking the nail head. In fact,
all we get is some arcing between the hacksaw blade and the paperclip
tipwhen they touch. the paperclip gets very hot. The wire coil on
the nail is coll to the touch.

No wonder the paper clips' getting hot with the short-circuit coil. You're
supposed to be using *insulated* enameled copper wire, which you can get
from RadioShack or most good electronic-component outlets.

I also tried two 6v batteries in series but no apparent change. I am
stumped with no idea what to try next, and my son is getting anxious
that he will have no project.

What is the coil of wire supposed to do?

It's supposed to work as an electro-magnet.

Does this have a name - it
looks like a motor winding? We used 24 gage wire - is this the wrong
gage?

The guage sounds correct, but it must be *insulated* wire.

does it matter? My son did the winding, so it is not perfectly
evenly distributed along the length of the nail. Does this matter? Did
we do too many or too few windings?

The exact number is not too important, as long as it's approximately right.

Total outside diameter of the
winding is probably about 1/2 inch max.

I assume we have a complete circuit or we would not get the arcing.

Yup the arcing is caused by the short-circuit.

Please help with any thoughts as the project is due this week. Thanks.

--
Michael Turner
Email (ROT13)
zvxr.gheare1963@ivetva.arg

 

[Byron A Jeff]

In article <9bb4ae36.0403211522.678b5d99@posting.google.com>,
SJTM <stephenmurphy@mindspring.com> wrote:
-I know nothing about electricity, but my 7 yr old wants to build an
-electric buzzer for his science fair.

I've done virtually the same project with my 7YO putting together a
simple telegraph.

- We followed instructions in a
-book from the library but no buzzer. Project seemes straightforward.
-Wrap uninsulated wire 200 times around a nail tacked into a board.
-Attach one lead to a simple metal bracket that holds the face of a 3
-inch piece of hack saw blade about 1/8 inch from the head of the nail.
- the other lead goes to a simple switch. The other switch contact runs
-to a battery, size unspecified but we used a 6 volt lantern battery.
-The other battery lead goes to a paper clip fastened to the based and
-bent to just touch a tip to the edge of the other face of the hacksaw
-blade.

Let me draw this in ASCII

Batt+ -> switch -> coil -> hacksaw -> paperclip -> Batt-

OK. Presuming that the paperclip and the hacksaw are touching, then when the
switch is pressed, the coil activates pulling the blade away from the
paper clip which then breaks the circuit. So then the hacksaw reverses
direction and recontacts the paper clip reestablishing the circuit again.

-
-In theory the electrical current should vibrate the hacksaw blade,
-causing it to buzz, appatrently by striking the nail head.

That should be fine because at the point where the blade contacts the head
of the nail, only residual current should be flowing.

The one thing that concerns me is that there is no current limitation anywhere
in the circuit.

- In fact,
-all we get is some arcing between the hacksaw blade and the paperclip
-tipwhen they touch. the paperclip gets very hot. The wire coil on
-the nail is coll to the touch.

Two problems:

1) Not enough pull from the coil. The circuit doesn't seem to be breaking.

2) No current limiting. When I did the telegraph, I put a 8 ohm 25W resistor
from the Radio Shack in series. It'll limit the amount of current pulled from
the battery.

-
-I also tried two 6v batteries in series but no apparent change. I am
-stumped with no idea what to try next, and my son is getting anxious
-that he will have no project.

Simple. Move the hacksaw blade closer to the nailhead. Here's a simple way to
test: attach the paperclip to the hacksaw so that they don't disconnect when
the switch is pressed. Now tune the hacksaw/nailhead distance so that when you
press the button the hacksaw blade actually clicks against the nail. Once that
works, then disconnect the paperclip so that it's again stationary when the
hacksaw blade moves.

BTW if I were doing this projects I'd abandon the paperclip and replace it
with a second nail above the hacksaw. More ASCII art:

N
N
HHHHHHHHHHHHHHHHHHH

C
C

N is the nail that replaces the paperclip, H is the hacksaw blade, and C is
the coil nail. Same action except that you get two nail clicks per cycle
which should give you a louder buzz. Tune the same way so get the correct
distance between the coil and the blade.

I'd still throw in the resistor before tuning. Your battery will last longer
because the resistor will limit the amount of current.

BAJ
-
-What is the coil of wire supposed to do?

Create a electromagin.

- Does this have a name - it -looks like a motor winding?

Electromaget or coil. Acts just like a relay, which BTW you can get to buzz
just as easily.

- We used 24 gage wire - is this the wrong -gage? does it matter?

Kind of complex, thinner wire has more resistance so it'll heat up more.
Thicker wire is harder to wrap tightly. It's probably OK.

- My son did the winding, so
- it is not perfectly -evenly distributed along the length of the nail. Does
- this matter?

In the large picture, probably not. Obviously it'll have an effect on the
magnetic properties of the coil.

- -Did we do too many or too few windings? Total outside
- diameter of the -winding is probably about 1/2 inch max. - -I assume we
- have a complete circuit or we would not get the arcing.

Not enough pull from the coil.... so

-Please help with
- any thoughts as the project is due this week. -Thanks.

...Get the hacksaw blade closer to the coil nail. Add some resistance. Test.

You'll get it.

BAJ