Fun simple circuits
September 19, 2019 8:31 AM   Subscribe

Am going to make some simple PCBs with young folks and let them then solder them. I am thinking a simple flashlight (battery, led, switch, resistor) is a good one, but there's got to be lots of fun litte things we can build ourselves.

We want to make our own simple pcbs to go with them (or freeform solder) rather than breadboarding or using established kits. Ideally I am throwing some components in a ziplock and letting them loose with an instruction sheet. Probably looking for less than 10 components, it's got to be cheap enough to give away and I also don't want to hand-drill through-holes for lots of components!
posted by J.R. Hartley to Technology (11 answers total) 6 users marked this as a favorite
Are telegraph keys and crystal radios too complicated?
posted by Botanizer at 9:04 AM on September 19, 2019 [3 favorites]

I think I would maybe go with something like a 555-timer based circuit that blinks a LED, where the speed and/or duty cycle is controlled by a potentiometer. I could help you with a circuit if you like, or they are probably common on the web. As far as parts you'd need
* a 555 timer (these are cheap in bulk)
* a few resisters
* an LED
* a potentiometer (or two if you want to control more than just the speed)
This might be too tough depending on how young they are, because 555 timers are 8-pin devices and you have to get the pins right or it doesn't work at all

A little "alarm" circuit might be fun. There are a few sensor types that would work to detect when two items are either close together or far apart. So you could imagine like you have a sensor on the wall and a trigger on a window, and if the window opens then they move apart and you trigger a tone or a light to indicate that. You could use any of:
* a hall effect sensor (detects whether a magnet is close or not)
* a photoresistor or maybe a phototransister (detects whether it sees light or not)
* a photointerruptor (sort of looks like a small horseshoe, detects whether something is inside the U part or not)
posted by RustyBrooks at 9:12 AM on September 19, 2019 [2 favorites]

Here are plans for a simple and inexpensive Morse code key using a clothespin. I haven't made these myself but they are apparently great for groups of young folk. As-written, it uses crimped connections without soldering, but of course those could be soldered instead.
posted by exogenous at 9:31 AM on September 19, 2019 [2 favorites]

Best answer: Came to recommend making a noisemaker with a 555, similar to RustyBrooks' recommendation -- it's a simple circuit, but throw on a potentiometer and a speaker and the kids can make annoying noises, somewhat funner than just making a light blink.
posted by AzraelBrown at 9:40 AM on September 19, 2019 [1 favorite]

Best answer: The Atari Punk Console is a fun, easy to build noise-maker circuit.
posted by bradf at 9:41 AM on September 19, 2019 [4 favorites]

One of my sons has one of the Snap Circuit kits and the 2 circuits he keeps going back to over and over are: a photosensitive noisemaker (brighter the light, the louder the sound), and a simple circuit that spins a little DC motor with a fan-thingie attached to it. He thinks these are hilarious.
posted by jquinby at 9:48 AM on September 19, 2019 [1 favorite]

Best answer: I just saw a kit to make a moisture indicator for house plants - I think you put some part of it in a potted plant, and a light comes on when the soil gets too dry.

Something else that's easy to do: hook 12V worth of batteries to a computer/CPU fan. The really cool part is that it's easy to make a solar charging circuit for a 12V marine battery - then you have a solar powered fan that you made yourself.
posted by amtho at 10:22 AM on September 19, 2019

Went to a father's day soldering thing with my kid at the Living Computers museum, they had pre-made circuit boards to which we soldered a battery holder, two LED's, and a pokey pin backing (like these). Then we walked around the rest of the day with fun blinking pins on our shirts.
posted by rouftop at 11:39 AM on September 19, 2019

Vibration motor "brush bots" have been a hit with local high school students with no electronics experience. You can get parts for 300 for around 60 bucks. Throwing in other components - plastic cups and stiff wire, felt pads, cardboard tubes, and some cheap hot glue guns - are fun. Competitive races sound like fun to me, but our students were absolutely not interested in the competition part.

(A 555 timer piano is my go-to for people who've already been through 10 hours of basic electronics. But, probably too much here.)
posted by eotvos at 12:37 PM on September 19, 2019

The check out anything by Forrest Mims for some good simple ideas.

my dad had this one (i think), and another one with a yellow cover I can't seem to find a picture of.

One I especially remember making from one of his books is a heads/tails generator with a 555, a momentary push button and a red and a green LED.
posted by ArgentCorvid at 2:53 PM on September 19, 2019

Best answer: I’ve helped kids through building a
joule thief

Have them bring dead batteries to test with, so you also get to teach voltmeter skills.
posted by unknown knowns at 5:53 PM on September 19, 2019

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