Home schools, scouts, and schools can browse this page, a menu of portable learning activities from Augusta Solder and Circuits.
John Engelbrecht johnenge@earthlink.net March 2012
A portable activity will generally be accompanied by a brief pitch about the lab-based, electronics and networking activities available at Solder and Circuits.
Sponsors can visit Solder and Circuits at 12311 Culebra Road #6104 San Antonio to preview. E-mail or call to make an appointment. All activities will be interesting-to-fascinating for parents, too.
$4 per ten miles travel charge from Grovetown. Fee, if any, to be discussed.
Electromagnet with flux lines—seven-pound electromagnet with steel core to show where flux lines go and why they spread out. Summer 2012. Application: generate voltage as in a generator, shield magnetism with a steel pipe, magnetize a needle to make a compass, Lenz's Law converting kinetic energy to heat in an aluminum conductor (similar to an induction motor). All activities are hands-on, one person at a time. Extension to motors, display a flat motor from a CD drive, feel torque in a stepper motor when a winding is shorted.
Electromagnet with flux lines—two six-inch-diameter, air-core coils to show where flux lines go. April 2012. Application: magnetic attraction and repulsion felt as you hold these coils in your hands, wiggling steel “cockroach,” flux-line demo with shredded steel wool, increase in flux when steel is in the path. All activities are hands-on, one person at a time. Steel wool shreds are sharp, care is required.
Prism—two three-inch, plastic prisms, and multiple samples of replica diffraction grating. Application: spread out sunlight or incandescent light into the visible spectrum. View effects of color filters. With replica diffraction gratings, view different angles of different colors of LEDs. View a neon lamp's bright lines. At night, view a mercury-vapor-lamp's bright lines as being different from neon. Try to identify the gas in various “neon” signs. All activities are by individual observing. Extension to quantum physics (hot solids spread out the lines but low-pressure gases and plasmas do not); solar and star observation, to detect elements and observe red shift; metallurgy, to detect alloys.
Molecular modeling—with a $130 kit, each participant builds molecules. Children and youth who are manipulative oriented will like this. There are enough parts for five participants. The brand is Molymod by Indigo Instruments. The molecules range from water to methane, propane, alcohol, sugar, fats, and amino acids. The burning of food in the body is easy to demonstrate. Oxidation of alcohol to vinegar is shown. Internet is used to get pictures of what to build. The polarization of water is an important extension. Fee: $2 per participant to cover wear and tear.
Temperature and light measurement electrically, using thermistors and cadmium-sulfide cells and volt-ohmmeter on ohms. Graph resistance vs. temperature or light intensity. Requires that participants interpret k and M as kilohms and Megohms, as in “scientific notation.” Five CdS cells and three thermistors are usable. The instructor can bring two multimeters, the group may wish to purchase others for $12 at Walmart or Radio Shack. (Digital is easy to read, analog is more convincing but requires learning how to read the scale.) An incandescent lamp is needed, also two pounds of ice in an ice chest and quadrille paper. All activities are hands-on. The pace must be slowed down to interpret kilohms or Megohms correctly and make neat graphs. Extension to thermostat: a small, interested group can be guided in a two-hour activity through use of transistors to regulate temperature.
Soldering, LEDs, diodes, resistors—an easy to understand use of electricity with LEDs. Lead-based solder is used and supplied by the instructor, but simple safety precautions are up to the host. Not in a kitchen or on a dining table. Ten years old minimum age recommended, hyperactive children will not be able to concentrate enough to be safe and produce good solder joints. Working surface to be covered with disposable paper. Instructor provides LEDs, solder, diodes, resistors, wire, printed circuit boards. Three weeks notice required to prepare printed circuit boards, or extend the session by three hours and let participants make their own, a very neat activity with wet chemistry. Parts are about ten cents each, boards are $2. 9 volt battery per participant, or instructor brings a power supply. One soldering iron and a calculator per two participants are needed, Radio Shack has irons. Adults must be present to help participants learn soldering and avoid getting burned. Extension to LED seven-segment displays. Participants will learn that diodes block in one direction and that resistors are needed to limit current. This activity does not develop a full understanding of circuits but gets partway there.
An extension for participants who are eager to go way beyond LEDs: two “diode folders” which have diode circuits. This gets into voltage drops vs. voltage with respect to ground. Voltages are applied to the power buses and meters are used to see if predictions are correct.
An extension: what is inside resistors.
Watts, lamps, and resistors—similar to the LED/diode activity above. This one uses Ohm's Law and power=volts * amps, calculators and simple algebra are required. Volt-ohmmeters are optional, the main activity is feeling temperature increase when power is applied. A non-soldering activity is available, for $10 fee the instructor brings a variable autotransformer to light up incandescent lamps at lowered voltage. Adult supervision needed for electrical safety for ages below 14, if incandescent lamps are used. Participants must be patient enough that every person in the group understands each point before going on.
Parallel and series circuits—at the end of this activity, participants will know the difference between voltage and current, parallel and series, and will be able to connect a power source to a switch and a lamp or resistor. They will verbally say the consequences of shorting a power source and contacting the body to 120 VAC power.
This activity can be from two to five hours. It is available for battery (safe) or 120 volt AC (requires close, adult supervision, about one adult per two students). The activities should be lined up in consultation between the sponsor and instructor, especially to supply low-voltage parts or, from Home Depot, 120 VAC switches, lamp sockets, and tools, which will be property of the sponsor. No measuring equipment is needed. Wire stripping and screwdrivers are needed.
An advanced activity is putting lamps in series to show different voltage drops, in which case a multimeter is needed. A more basic activity is switches with parallel and series loads. Dilemma: why do the highest-watt lamps in a series string glow the least?
The learning here is extended to how wall switches and room lights are wired, and how a table lamp puts the lamp in series with the switch. For the table lamp, an ohmmeter measures the lamp resistance when the switch is on.
An extension is a battery applied to a speaker. The DC extension or sucking in of the cone is seen.
An extension is the wiring of two two-way switches to control one light. This is often done in homes and is a good puzzle. This activity works best when the sponsor supplies three two-way switches and we open up one of them to see the insides.
Stepdown transformer—a stepdown transformer is used on 120 VAC to obtain a safer voltage. A ferrite, four-winding transformer is used with earphones to do step-up and step-down at audio frequency. Application: any consumer device that uses a heavy, plug-in power pack. (The light weight power packs have switching regulators, not a 60 Hz transformer.) Needed: multimeter.
This can be extended to how it works, but just the fact of stepdown is valuable knowledge. It is easily extended to the pole-mounted, residential, cylindrical transformer that gets 12,500 VAC down to 120 VAC.
This can be extended with diodes and a capacitor to make a DC supply that has a good amount of power. All the parts are at Radio Shack, but the instructor can bring what is needed. If the household has an old VCR or DVD, we can take off the cover and identify the transformer, diodes, and capacitor.
Solenoid, relay—these electromechanical parts are simple and interesting. There is no science, here, it is just how they work. Both parts use magnetic flux. Real parts are used.
Stereo speakers and amplifier—the instructor brings The Speaker Chair, an infinite-baffle enclosure with stereo speakers. The Speaker Chair is at once a chair and a low-cost, homemade speaker enclosure, made from cardboard boxes. The stereo amplifier is also homemade. A learning objective is how an infinite baffle works. An extension is looking at Internet to see how to make a bass reflex enclosure. An extension is talking over how participants would build their own, low-cost enclosure if they wanted to.
Besides removing the back and seeing how the audio changes, and looking inside the speaker enclosure to see how cheapness can give good performance, audio trials are held to demonstrate series, parallel, and phasing. The IASCA Sound Quality Reference CD is used in the household DVD or CD player. An audio oscillator is used to let participants sweep frequency and listen for resonances. (Disconnect one channel and apply a two-foot cardboard tube to hear resonance for sure.)
Participant patience is a plus for this activity. The instructor will attempt to prevent audio fun from getting in the way of learning.
A fee of $5 covers wear and tear on the enclosure.
Cascaded audio amplifiers—homemade, gain-of-ten, audio modules, quantity four, are used by one participant at a time to amplify an XLR microphone, with a speaker output. The instructor asks participants for ideas about how to get the best amplification, considering that several different wiring schemes are possible. There is an application of addition and multiplication. A learning objective is to know how feeble a microphone signal is and how great the amplifier gain must be to power up a speaker.
The homemade equipment is designed for resistance to damage in case of wrong connections.
An extension is audio feedback (the squeal of PA systems).
Another audio amplifier activity—related to the above but using different equipment. One electronic box contains four amplifiers that may be cascaded. There is an XLR microphone input (a microphone comes with the activity) and a 1,000 Hz test tone at three different voltages.
An extension: the amplifier box has significant supply buzz. Discussion is held about why this is and how sensitive people's hearing is.
Pipe resonance—a microphone and a small speaker in eight feet of plastic pipe are used to find acoustic resonance. Quadrille paper and calculators are used. Participants research on Internet beforehand the speed of sound in air, the formula for wavelength in terms of speed of propagation and frequency, and the relation of wavelength to pipe length for open and closed pipes. Calculators are used.
Extension: another microphone and amplifier are used with AC voltmeter to measure amplitude of resonances.
Ohm's Law—participants use multimeters, a battery, and resistors to prove Ohm's Law. An extension is the power equation. Simple algebra is a plus. A calculator per person is needed. This works best if each participant, or each pair, has a battery and a meter ($12 or more from Radio Shack or Walmart).
An extension: the instructor brings some nichrome wire (4.68 ohms per foot), and we see that wire resistance has a real effect.
An extension: D'Arsonval meter.
A plus: participants research Ohm's Law on the Internet before the activity.
Operational amplifier—a mysterious, forty-cent electronic part does math functions. A real op amp is built into a demonstration unit. Participants use clip leads to apply resistors, input voltages, and a meter to see that it works. An extension for middle-school and later, for those who know Ohm's Law, is why it works, and practical applications. Preceded by research on Internet: operational amplifier, feedback.
Transistors—some (not all) basics of transistors are used to make simple amplifiers. The emphasis is on common emitter and emitter follower. NPN power transistors and resistors are used with capacitors, speakers, and power supplies. This is an advanced activity. Ohm's Law, current, voltage, and power are prerequisite knowledge. Several multimeters are needed. An extension: the concept of source and load impedance. One circuit is built by the group, one person is hands on at a time while others check against a schematic.
HTML orientation—simple HTML files are written in a text editor (no special software at all is needed). This is done starting with a known-good HTML file. The text is changed and photos are added. Custom colors are used in text and background. Each participant needs a computer with a web browser. Note: Google Sites are free, and you can upload your HTML if you wish.
Frequency mixing with audio oscillators—this advanced activity uses two audio oscillators. First, participants listen to the oscillators and tune up octaves, then tune up beats where the frequencies differ slightly. Next, mixer diodes are used to mix two frequencies, and the sum and difference are listened for. (This gives neat, sci-fi type sounds.) Extension: trig (product of two sines). Extension: use a household's electronic keyboard and check the calibration of the oscillators.