For my son’s 8th birthday party, we had nine 8-year-olds over, and I prepared an electronics activity for the kids. We called it a “Science” party.
The central projects were based on these blinky circuits, one using a pair of 3904 NPN transistors and the other using a 555 timer.
We started with three very simple projects:
- Connecting a 9V battery to an LED using a resistor.
- Add a pushbutton.
- Add a potentiometer (dimmer).
We then moved on to the blinky with the 555 timer. Here’s a photo; the two LEDs flash alternately, with the speed controlled by a potentiometer:
Here’s a photo of the fifth project, a blinky using two 3904 transistors. The kids didn’t get to this one.
I’d originally intended to do the blinky with the transistors and then the one with the 555 timer, but the transistor circuit proved to be more complicated, so I left it to last, and I was pretty sure we wouldn’t get to it anyway, and we didn’t.
I ordered a bunch of parts from All Electronics, including a breadboard, LEDs, resistors, capacitors, battery snap, potentiometer, 555 timer, and 3904 transistors.
Here’s the parts list, which came to $8/kid.
(I got a few extra resistors, LEDs and another capacitor (for another $0.87/kid), because I wasn’t quite sure what I was going to do at the time I placed the order.)
I prepared a detailed handout (PDF here) with explanations of the different parts and breadboard diagrams for five projects.
Each kid got a ziploc bag with all of the parts and two paper plates to lay them out. Here’s a picture:
I didn’t really explain anything. I just told the kids to flip ahead to the first project and try to set it up.
A bit of soldering
The potentiometer I got was nice and big, with a handsome knob, but it didn’t fit into the breadboard, so I had to solder wire to two of the leads for the kids to use it.
I should have gotten the kind that was intended for soldering, but I wasn’t thinking clearly when I placed the order.
I also had soldered solid wires to the battery snaps, so they’d be easier to insert into the breadboard. I also clipped a bunch of different jumper wires of different lengths and colors.
The soldering and wire clipping were a lot of work. But I could use the soldering practice, and I kind of like stripping wire.
Both my kids enjoyed distributing the different parts into the ziploc bags. In other words, they fought over who could do it and whether one had gotten to do more than the other.
Lots of assistants
My wife, my father, my father-in-law, one of the guest’s dad, and I were helping the kids. We had an assistant for every two kids, and that made a big difference.
I think everyone got the first three simple projects to go without any trouble, but the fourth project, the blinky with the 555 timer, proved frustrating for many.
A couple of kids gave up and pulled all of the parts out of their breadboards before I had a chance to go over and troubleshoot. (And it’s tricky to look at someone’s layout and figure out what is wrong.)
One of the kids that I was helping had several problems: the 555 IC was backwards, one of the LEDs was backwards, and one of the resistors wasn’t in the right place. I fixed all that, and it still didn’t work. Finally I discovered that the jumper from pin 3 on the IC to the battery was missing.
One girl did do the whole layout herself, hooked up the battery, and it worked perfectly on the first try. That was nice to see.
The rest of the party
The party was planned to be 90 min. The first 30 min the kids played outside. They were running around like crazy, actually; we wondered if they would be able to settle down and work on the electronics. But they did come in and concentrated nicely on the breadboards for 30 min, and then went off to play some more, giving us a chance to clean up (organizing all of the goodies into bags, with fruit snacks, to take home) before the cupcakes (four dozen for 10 kids is the right amount).
Room for improvement
The party was successful. I think the kids enjoyed playing with the electronics. I wish I’d gotten them all to do the blinky successfully, but I’m happy that at least some did.
I had a couple of example layouts for the kids to look at, but just one of each of the 4th and 5th projects.
If I were to do this again, I would:
- Have a couple of examples of each of the projects, for the kids to look at.
- I clipped the leads on the capacitors rather than peeling them off the tape, making them hard to work with. I should have left them with longer leads.
- Use an easier-to-solder potentiometer.
- Maybe just toss the 5th project completely.
- Include wiring diagrams in the handout, in addition to the breadboard layouts.
- Put the parts explanations at the back of the handout.
- Have more explicit and complete instructions, at least for the first three projects.