B
BZ
- Jan 1, 1970
- 0
Hi everyone,
Thanks for the kind and helpful answers to my questions last week.
After about 12 hours of bumbling with wires and diodes, with
resistors and switches, with solder and electrical tape and
hot glue, the project is finally complete, and even works.
My daughter's atom was Argon, with 18 protons, 18 electrons,
and 22 neutrons. A 9V battery would only power three LED's at
a time, and using AC was not an option, so we ended up buying
a five year supply of batteries at Sam's and building 20
identical circuits on the back of the foam board. We have 20
9V batteries taped along the bottom of the back, and the wires
are a mess of spaghetti like you've never seen. Somehow we
managed to use about 75 feet of wire on the back of a single
poster-board sized sign. The only thing messier than the
wiring is the tape job holding the excess wires down. The
back of this looks like it was built by a chimpanzee in a hurry.
To make the connections we twisted the wires together tightly
and taped them down, and the connections seem reliable. The
only connections that we soldered were the battery leads,
because the battery lead wires were so flimsy they would never
hold without solder, and I didn't trust a wire nut on these.
Although I'm an electronic design idiot, I've done a lot of
soldering in the past, and am actually pretty good at the
mechanics of getting a good solder joint. I didn't want to do
200 solder joints if I could avoid it, and got away with doing
only 40, with me holding the soldering iron and my daughter
applying the solder. She's become quite adept at applying
solder and at cutting and stripping wire. (We've already
discussed her taping skills...)
We ran into an expected problem with the nucleus, where we had
40 diodes packed shoulder-to-shoulder in a 2" diameter circle.
After making all the necessary connections, we tried taping
down the naked diode leads layer-by-layer to prevent
short-cicuits, but it kept shorting out anyway, and we had to
pull up all the tape twice. Eventually we used hot glue to
encapsulate and isolate the naked diode leads, and that worked
like a charm.
From the front it looks great -- a black foam board with 18
green LED electrons in orbits drawn using silver Sharpie
markers, with a random grouping of 22 red and 18 yellow LED's
in the center for the nucleus. Each subatomic particle type
has a rocker switch on the front to turn them on and off. The
LED's aren't as bright being three in series as they are with
only two, but they're fine. Because we have a total of 58
LEd's, we do have a couple sets of two diodes in series, and
you can tell from the front which ones they are. (Don't even
think of trying to figure it out from the back!)
My daughter now knows a lot of electronics for a sixth-grader
-- in fact, thanks to this project I think she learned more
electronics than chemistry during this chemistry unit. Her
best friend in the class, meanwhile, is instead learning how
hard it is to glue a colored marshmallow to a piece of poster
board.
If I had it all to do over again, I would try what Spehro and
Chris both suggested, and do fewer circuits in parallel.
Being a simple-minded sort, however, I went with the simplest
circuit I could and just did the same thing over and over
again. I'm sure it cost me more in time and in battery
expenses and isn't as elegant as their solution (especially
since with their designs I could have wired the LED's two in
series instead of three and gotten brighter light), but it was
probably better for my daughter's education to build the same
simple circuit over and over. She can explain that circuit
pretty well in case the teacher asks, and it will be evident
that she learned a lot doing this.
Thanks again for the help!
Thanks for the kind and helpful answers to my questions last week.
After about 12 hours of bumbling with wires and diodes, with
resistors and switches, with solder and electrical tape and
hot glue, the project is finally complete, and even works.
My daughter's atom was Argon, with 18 protons, 18 electrons,
and 22 neutrons. A 9V battery would only power three LED's at
a time, and using AC was not an option, so we ended up buying
a five year supply of batteries at Sam's and building 20
identical circuits on the back of the foam board. We have 20
9V batteries taped along the bottom of the back, and the wires
are a mess of spaghetti like you've never seen. Somehow we
managed to use about 75 feet of wire on the back of a single
poster-board sized sign. The only thing messier than the
wiring is the tape job holding the excess wires down. The
back of this looks like it was built by a chimpanzee in a hurry.
To make the connections we twisted the wires together tightly
and taped them down, and the connections seem reliable. The
only connections that we soldered were the battery leads,
because the battery lead wires were so flimsy they would never
hold without solder, and I didn't trust a wire nut on these.
Although I'm an electronic design idiot, I've done a lot of
soldering in the past, and am actually pretty good at the
mechanics of getting a good solder joint. I didn't want to do
200 solder joints if I could avoid it, and got away with doing
only 40, with me holding the soldering iron and my daughter
applying the solder. She's become quite adept at applying
solder and at cutting and stripping wire. (We've already
discussed her taping skills...)
We ran into an expected problem with the nucleus, where we had
40 diodes packed shoulder-to-shoulder in a 2" diameter circle.
After making all the necessary connections, we tried taping
down the naked diode leads layer-by-layer to prevent
short-cicuits, but it kept shorting out anyway, and we had to
pull up all the tape twice. Eventually we used hot glue to
encapsulate and isolate the naked diode leads, and that worked
like a charm.
From the front it looks great -- a black foam board with 18
green LED electrons in orbits drawn using silver Sharpie
markers, with a random grouping of 22 red and 18 yellow LED's
in the center for the nucleus. Each subatomic particle type
has a rocker switch on the front to turn them on and off. The
LED's aren't as bright being three in series as they are with
only two, but they're fine. Because we have a total of 58
LEd's, we do have a couple sets of two diodes in series, and
you can tell from the front which ones they are. (Don't even
think of trying to figure it out from the back!)
My daughter now knows a lot of electronics for a sixth-grader
-- in fact, thanks to this project I think she learned more
electronics than chemistry during this chemistry unit. Her
best friend in the class, meanwhile, is instead learning how
hard it is to glue a colored marshmallow to a piece of poster
board.
If I had it all to do over again, I would try what Spehro and
Chris both suggested, and do fewer circuits in parallel.
Being a simple-minded sort, however, I went with the simplest
circuit I could and just did the same thing over and over
again. I'm sure it cost me more in time and in battery
expenses and isn't as elegant as their solution (especially
since with their designs I could have wired the LED's two in
series instead of three and gotten brighter light), but it was
probably better for my daughter's education to build the same
simple circuit over and over. She can explain that circuit
pretty well in case the teacher asks, and it will be evident
that she learned a lot doing this.
Thanks again for the help!
