# Home school circuit analysis class suggestions needed

#### rpschultz

Joined Nov 23, 2022
265
A friend of mine teaches a high school circuit analysis class to home schoolers. They meet once/week. 15 boys age 14-17, my 14 yr old son included. My friend (40) just got diagnosed with a brain tumor, 3 young kids. Ug. But we are hopeful, he’s still in the diagnosis stage.

I offered to teach the 2nd semester for him. I’m a mechanical engineer who has dabbled in electronics for 25 years. Guitar amps, pedals, etc. I recently designed a circuit here on AllAboutCircuits; a condenser mic preamp/HPF for my guitar. Schematic, sim and layout in Eagle. Prototype PCB being made currently at Osh Park.

First semester the kids got a lot of the basics. For the 2nd semester I’d like to shift focus and make it more hands on. I’d like to teach them to solder and by the end of the semester for them to build a circuit of their choice. They could copy a circuit they find on the internet, buy/build a kit, or design their own. The class will learn Eagle and put their circuit through Eagle Spice.

They all have an Arduino board in their packet and I should be able to acquire enough multimeters for everyone. Amazon has decent looking solder kits for $12/ea. I have a decent supply of resistors, caps and pots. Can acquire LEDs, op amps, transistors, etc as necessary. I taught HS physics a long time ago, so I know the challenges of doing a lab in 50 minutes. But I’m open to advice. I’d also love project suggestions for me to give to the class. What type of circuits are cheap (<$25?!?) and easy to build, yet still cool?
Thanks!

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#### AnalogKid

Joined Aug 1, 2013
10,176
There are tons of 555 beeper and flasher circuits. For more advanced students, try one that has fully independent on-time and off-time adjustments.

Or, an all-discrete beeper / flasher circuit using the classic two-transistor multivibrator circuit.

Photo-electric switch, such as a broken-beam detector. (my first science fair project)

An audio oscillator driving a small speaker - 555 / phase-shift oscillator / lotsa options.

Can you give us an approximate skill level for your group so we can try to match the technical complexity? Number of soldered connections / number of passive components / IC's versus transistors - ?

Where are you located?

ak

#### rpschultz

Joined Nov 23, 2022
265
Knoxville TN
I doubt if any of them have soldered yet.

Joined Jul 18, 2013
26,291
Knoxville TN
I doubt if any of them have soldered yet.

#### MrChips

Joined Oct 2, 2009
27,695
One project that I think is doable is a clap activated light.
Clap once and an LED turns on.
Clap again and the LED turns off.
It incorporates analog circuits, amplifiers, filters, and flip-flops.

#### rpschultz

Joined Nov 23, 2022
265
Right. Their kit has a small breadboard. Definitely a first step.

#### rpschultz

Joined Nov 23, 2022
265
One project that I think is doable is a clap activated light.
Clap once and an LED turns on.
Clap again and the LED turns off.
It incorporates analog circuits, amplifiers, filters, and flip-flops.
hey that sounds cool. Could you provide a link maybe?

#### MrSoftware

Joined Oct 29, 2013
2,059
Also get yourself a classroom set of flux, side cutters, alcohol, acid brushes (for cleaning flux), alcohol, solder wick, safety glasses.. Use leaded solder, it's much easier for beginners to work with than lead free.

#### AnalogKid

Joined Aug 1, 2013
10,176
This circuit is missing a pull-down resistor at the 555 Trigger input (to the right of the 100 nF differentiating capacitor). Without it, the circuit will not work reliably. Random innergoogle schematics abound with problems such as this. As you narrow down the number of circuits you want to bring to the class, you might want to run them by us as a sanity check.

Side note: Something important to teach - reference designators! Without them, discussing the operation of a circuit is cumbersome, ambiguous, and, well, "dangerous" might be too strong; how about "fraught with peril"? Which is more clear, "the 100 nF differentiating capacitor" (which assumes that there is only one such part in the entire schematic), or "C1"? Reference designators probably are the only "rule" of schematics more important than: Grounds ***always*** point downward.

ak

#### crutschow

Joined Mar 14, 2008
31,128
This circuit is missing a pull-down resistor at the 555 Trigger input
It needs to be a pull-up resistor to Vcc since the 555 triggers with a low level input pulse (here provided by the transistor).

#### AnalogKid

Joined Aug 1, 2013
10,176

#### AnalogKid

Joined Aug 1, 2013
10,176
Just remembered this. It might be a bit advanced for a grade school class, but ...

You can buy a kit that is an all-discrete 555 - a pc board with transistors and resistors that is an exact copy of the original 555 internal schematic. Probably outside your budget, and maybe too many parts to debug if something doesn't work. But if you have an advanced student who wants to build a 555 flasher, this is the ultimate.

ak

#### rpschultz

Joined Nov 23, 2022
265
Use leaded solder, it's much easier for beginners to work with than lead free.
Soldering iron kit, 60W soldering gun, 9-in-1 solder iron kit tool, adjustable temperature from 200 to 450℃, 5 soldering iron tips, solder wire, soldering iron stand for soldering and repair https://a.co/d/10uFgJm

I was gonna buy one of these for everyone. Q&A says it’s leaded, 2% flux. Open to other suggestions.

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#### MrSoftware

Joined Oct 29, 2013
2,059
Wow the price is right, that's for sure. Constructive criticism on what I see: I suspect that stand is going to be a challenge (it's going to fall out a lot when the kids bump the cord), the temperature selector most likely is not accurate and the hand piece might be on the large side, but for the price it might get the job done and be "good enough". Order one and test it.

If you can spring a few more bucks, this kit (click here) adds side cutters, tweezers, chore boy style tip cleaner and some brushes for removing flux. It includes a sucker too, which will be important if you're doing through-hole stuff. The stand looks better in the photos, but I'm guessing it's going to fall over easy, but again for the price that's a lot of stuff.

Here's another inexpensive kit, no side cutters (you can get a few classroom pair for a few bucks), but adds the solder wick and some other goodies. And here's one with a multi-meter! I can't believe how cheap these kits are, I wonder if they really work!?

Maybe buy one of each and test them out, if you've got the budget. After testing they can be added to the classroom pile.

Reflecting on my own childhood; I predict the kids will overheat the solder frequently, or just take too long, and vaporize the flux, which is going to make the solder pasty and frustrating to work with. All you have to do is add some flux to the joint and you're back in business. This is my personal favorite, fantastic stuff, maybe get a tube for the classroom. Get a roll or two of solder wick for the classroom too, I've used this one and it works well.

You're going to want some sort of way to clean up flux. Plain old isopropyl alcohol works great, 70% works fine and won't be AS flammable as the 99.9% stuff. Maybe get a few of these dispensers to spread around the classroom, and some little brushes. To clean flux, get the brush wet with alcohol, scrub the flux, lay a clean paper towel over top then brush it again with a wet brush and presto clean.

I hope this helps!

#### rpschultz

Joined Nov 23, 2022
265
I gotta admit, I don’t understand flux. I’ve soldered for 25 years as a hobby-ist, just never used it. I clean the tip frequently and somehow make it work.

I should learn this part of it so I can teach it better.

#### rpschultz

Joined Nov 23, 2022
265
LDK Soldering Iron Kit, 30g Solder, Solder Paste, Heavy Duty Holder, Cleaning Sponge, 5pcs Replacement Tips, Electric 60W 110V Adjustable Temperature Soldering Gun Welding Tools https://a.co/d/1VhA1i4

This one has the better stand

#### rpschultz

Joined Nov 23, 2022
265
Soldering Iron Kit - Soldering Iron 60 W Adjustable Temperature, Solder Wire, Tweezers, Soldering Iron Stand, Soldering Iron Tips Set, Desoldering Pump, Solder Wick, Heatshrink Tubes [110 V, US Plug] https://a.co/d/8x0n0iz

I didn’t really want to spend this much (14 kids), but it has a lot of good stuff.

Id like to keep it to roughly $50/kid. So$19 for the soldering kit leaves about \$30 for any build kit and miscellaneous supplies. Seems reasonable.