two electronic kits and their applications for teachers (a...

Two Electronic Kits and their Applications forTeachers

(A Shocking Experience!)

Kim BrownNE R-IV School

[email protected]

Melissa HallIberia R-V

[email protected]

Final Project forSummer Physics InstituteElectricity and MagnetismDr. Meera Chandrasekhar

University of Missouri-Columbia

June 28, 2000

TwoElctronic Kits and The Applications For TeachersKim BrownMelissa Hall

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In this paper you will find information on two separate electronics kits:The Tingler Kit and The Plant Soil Monitor. We have each written teacher pages andstudent pages.

Here is how both kits compare:Both kits have the same basic concept of a circuit board with a conducting metal, atrimmer resistor, basic resisters, and a specialized IC chip. In both kits, a trimmer resisteris varied, which allows for different settings and possible outcomes.

Here is how the kits are different:The Tingler has a touch plate where the Soil Monitor has a copper-like probe. The SoilMonitor has a switch, and LEDs, while the Tingler has a light only to show that current isflowing. The Tingler delivers a mild shock, while touching the probe does not cause anysensation.

The Tingler

TEACHERS PAGESDescription of DeviceThe Tingler Kit tests the amount of current that can be felt in your fingers. Two fingersof the same hand are placed on the pads, and a trimmer resistor is used to vary thecurrent.

How the Device WorksA 9 Volt battery provides direct current, which is converted to alternating current by a555 timer IC chip. At the lowest trimmer resistor setting (Wimp), a transistor amplifiesthe signal, which lights the bulb. The person being tested feels a slight tingle. Severalresistors control the frequency of the alternating current. As the trimmer resistor settingis increased to the Hero stage, the person feels more current in the form of a strongershock.

Qualitative ApplicationsWe have observed different tolerance of the shock in two categories: tolerance amongdifferent people and tolerance of the same person in different situations.

Different people: (same situation)Female versus male, different sizes of people, age, time of day, and location allproduce different results within the same test.

Same person: (different situation)


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The same person under different conditions of humidity, saltiness of skin, leftversus right hand, or time of day all seem to make a difference when varied forthe same person.

We conclude that many factors affect a person s conductivity and tolerance ofshock.

Since we are electro-biochemical beings, conductivity through our bodies mustdepend on several factors.

Further Qualitative options for your studentsTest the relative amount of shock each student perceives at different times of day,in different locations in the room or school, and at different temperatures orhumidities in the school. Test at what point the student lets go of the touch pad.

Have students research nerve impulses, the electricity of weather, human skin andconductivity when wet versus dry, the history of the use of electric current, or theuse of the electric chair.

Have students design a way to wire your seating chart to this touch pad so thateach student could receive a shock, or the entire class could receive a shock justfrom you touching your seating chart.

Quantitative Measurements:Turn qualitative measurements into quantitative ones by having the students keeptrack of the responses based on boys versus girls, age, places, etc. Graph data.The problems with this are that there are so many variables, and the varioussettings on the trimmer resistor are too obscure. Students could be lead toevaluate these tests for the correct use of the scientific method.

Students with more electronics skills could wire a timer into the circuit to getmore accurate measures of how long they can take the current at each level.

Use Ohm s law to calculate the current felt by the person at the high and lowresistance. We collected data on this concept. A person s resistance is measuredby the person holding the two probes of a multimeter with the settings to Ohms.The two probes are then placed on the touch pads with the multimeter set to volts.This is done with the trimmer resistor set on the lowest setting, then repeated onthe highest setting. The current that would flow through the person at that timecan be calculated with I = V/R. This data can be charted and graphed.

The following is some of the data we collected

**(All Ohms x 100,000 and all current I x 0.000001 amps)


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Table 1: R, V, and I for June 21, 2000 at 3:30 pm. All adult.Person R (Ohm ) V (low) I (low) V (high) I (high)Eric 600 2.75 4.5 18.75 31.2Dan 450 2.75 6.1 18.75 41.6Kelly 470 2.75 5.8 18.75 39.8Melissa 900 2.75 3.0 18.75 20.8Kim 900 2.75 3.0 18.75 20.8

Table 2: R, V, and I for June 22, 2000 at 9:00 am. All adult.Person R (Ohm) V (low) I (low) V (high) I (high)Eric 1,800 2.72 1.5 18.75 10.4Dan 6,400 2.72 40.0 18.75 290Kelly 1,600 2.72 1.7 18.75 11.7Melissa 1,800 2.72 1.5 18.75 10.4Kim 1,600 2.72 1.7 18.75 11.7

Table 3: R, V, and I for June 22, 2000 at 3:30 pm. All adult.Person R (Ohm) V (low) I (low) V (high) I (high)Eric 480 2.90 6.0 18.75 39.0Dan 850 2.90 3.4 18.75 22.0Kelly 500 2.90 5.8 18.75 37.5Melissa 2,550 2.90 1.1 18.75 7.30Kim 1,920 2.90 1.5 18.75 9.70

Table 4: R, V, and I for June 23, 2000 at 3:30 pm. All ages.Person R (Ohm V (low) I (low) V (high) I (high)Heather (12) 480 2.45 5.1 17.50 36.4Jessica (13) 444 2.45 5.5 17.50 39.4Andrew (15) 1,500 2.45 16.0 17.50 11.6Jeff (40) 2,250 2.45 10.0 17.50 7.7Kim (40) 1,850 2.45 3.0 17.50 9.4

Table 5: R, V, and I for June 24, 2000 at 3:30 pm. All ages.Person R (Ohm) V (low) I (low) V (high) I (high)Heather 600 2.60 4.3 18.25 30.4Jessica 500 2.60 5.2 18.25 36.5Andrew 1,250 2.60 2.0 18.25 14.6Jeff 2,750 2.60 0.9 18.25 6.6Kim 1,990 2.60 1.3 18.25 9.1

The following graphs are to be expected:

If one table s data is graphed, as the voltage increases the current felt wouldincrease, assuming the resistance would stay the same. This graph would have Von the horizontal axis, current on the vertical, and would yield a directrelationship (a straight line).


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Comparing two tables for the same people with similar voltages, the resistanceand current should be in an inverse relationship. This graph would show R on thehorizontal axis, current on the vertical, and would yield an hyperbola.

Other suggestions for quantitative testsHave students measure their resistance before and after exercise and before andafter drinking an electrolyte such as Gator-ade. Dan s very high numbers onemorning came after a running session when he was depleted of electrolytes.Students should NEVER test their resistance after dipping their fingers indifferent solutions or substances. WET FINGERS WILL GREATLYREDUCE THE RESISTANCE, WHICH WILL GREATLY INCREASETHE CURRENT. Humans feel pain from 0.005 to 0.01 amps, and as little as0.07 amps can kill. A wet person can have a resistance as low as 200 ohms,which could give them a shock range of 0.01 amps on low (2.75 volts) to 0.09amps (18.75 volts). Do NOT let students do any testing that involves wet skin!

Assembly InstructionsA. Assemble the required parts:This kit can be purchased from Omnitron Electronics at 1-800-8888. It sells for

$9.95. It comes with all the parts needed to create the circuit, which include: 1 — 1 micro F electrolytic capacitor (C1) 1 - 555 timer IC and socket (IC1) 1 - Neon lamp (L1) 1 - 10K slide trimmer resistor (P1) 1 - 2N3904 NPN Transistor (Q1) 4 Resistors: one each of 6.2K ohms (R1), 12K ohms (R2), 39 ohms (R3), and 2.2K ohms (R4) 1 — Inverter transformer (T1) Miscellaneous: PC board, 9V battery snap, touch plate, insulated wire, rosin core solder, and a solder gunB. Directions: (Figures are at the end of this paper)1. Obtain a circuit board or create one in the correct pattern. (See Figure 1)Computer programs are available which will help in the design and constructionof such projects.2. Using the layout of the project (seeFigure 1), install the IC socket, P1, and C1.OBSERVE the locating mark on the IC and polarity on the C1. Make sure themetal legs of the IC socket contact the copper on the back of the PC board.Gently bend the prongs down and solder them. The short leg of the C1 goestowards the negative of the battery. ( Install means to place the object and thensolder the connection.)3. Install the neon lamp (L1).4. Install all resistors, observing the color code as shown in Figure 2. Forexample, the R1 resistor shows blue, red, red, gold. This would resolve to thefirst digit of 6, the second of 2, then multiply by 100. The gold tells the tolerance


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of 5%. Follow this same procedure to identify the resistors and place them in thecorrect spot on the board.5. Install Q1 with the flat side as shown on Diagram 2.6. Cut out the label (Figure 3) and glue this to the board in the correct place.7. Install transformer T1, using the locating mark as shown in Diagram 2.8. Install the touch plate using insulated wires. Install the battery snap, observingthe + and — directions.9. Insert the IC1 chip into the IC socket, observing the mark.10. Connect the battery to the snap. Remove the battery when not in use in orderto save the power.11. Put the P1 resistor on the lowest setting (Wimp). The light L1 should slightlyglow to prove that current is flowing. Have the subject place two fingers from thesame hand on the touch pads. The light should go out and the subject should feel atingle.12. Pushing the switch of P1 towards the Hero setting will increase the currentand therefore the tingling sensation.13. A schematic of the electronics is included as Figure 4.

Details of Components:Capacitor: A capacitor stores charge or acts as a filter. In this circuit it acts as afilter to only allow direct current to flow into the 555 timer IC chip.555 timer IC chip: This chip converts direct current from the battery to thealternating current needed for the transistor.Trimmer resistor: This resistor varies the resistance in the circuit so that thecurrent across the touch pads will vary. On the lowest setting the subject feels thelowest tingle, and on the highest setting the subject feels the most tingling. As theresistor switch is moved up, the actual resistance in the circuit at that pointdecreases, so the current increases. This observes Ohm s law (V = IR).NPN Transistor: This transistor acts as an amplifier. Two types ofsemiconductor materials exist as three layers. In the P type the hole moves, andin the N type, the electrons move, so with the combination there is always somecharge movement. The transistor is actually like two diodes. Both types (theother is PNP) have a base, a collector, and an emitter. In this case, the voltage isacross the base, and the electrons move from the collector to the emitter. Thiscauses a large current, there is a large change in the voltage drop across the outputresistor (R4), so the signal to the touch plates is amplified.Resistor: A device that limits the current in the circuit. R1 and R2 cause thevoltage to drop before it enters the IC chip. This sets the frequency at which thealternating current will oscillate when it exits the chip. The R3 resistor limits thebattery output. The R4 resistor limits the alternating current as it comes out of theIC chip. The trimmer resistor has been discussed above.Inverter Transformer: This is a step-up transformer, which increases thevoltage of the alternating current. Two coils of wire (the primary and secondarycoils) are interwoven or linked by a soft iron core. As the alternating currentflows into the primary coil, the changing magnetic field it produces will start analternating current voltage of the same frequency in the secondary coil. The


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output voltage depends on the number of coils; more coils on the second coilmakes this a step-up transformer. If more coils were on the first coil, it would bea step-down transformer that reduced the output voltage.

Student Page1. Instructions:A. Make the circuit as directed in the kit.B. Make qualitative measurements by testing everyone in your group to see if

age, location, time of day, etc determine how much of a shock you feel. Youare limited only by your imagination. Keep your data in a table.

C. Make quantitative measurements with a multimeter. Measure each person sresistance: place the multimeter on ohms, and hold each probe in one hand.Record the information. Then place the meter on volts, and measure thevoltage across the touch plates with the Tingler on the lowest setting. Repeatthe voltage measurement with the Tingler on the highest setting. Record thevoltages and calculate the current you would feel at each point.

D. Design an inquiry lab to see the effects of exercise and/or ingesting a sportsdrink on your resistance. Complete an inquiry diagram to show theindependent variable, the dependent variable, and your data.

2. Illustrations See the figures that accompany this sheet (Figures 1-4 for the Tingler).

3. Guiding Questions1. Briefly outline the path of the charge in the circuit.2. Which causes you to feel the tingle, the voltage or current? Explain.3. The same person can feel different shocks in different situations, even on

the same setting. Explain.4. Compare and contrast human electrical impulses with a circuit.


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Plant Soil Monitor Kit

Teacher Pages

Description of DeviceThe Plant Soil Monitor allows the student to test the conductivity of the soil. The controlresistor (Labeled P1) adjusts to calibrate for a known amount of water in the soil. Whenthe probe is inserted into the unknown soil with the push button activated, one of twoevents will occur: The green or the red LED will be lit.


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How the Device WorksA 9V battery provides direct current to the monitor while the trimmerresistor sets the calibrated level of conductivity that will be tested. The copper probe isinserted into the soil and the push button switch is closed. If there is not enough waterpresent, the resistance of the probe will be higher than what the unit was calibrated for.This will cause the current to flow along the path that will light the red LED. If the soilhas sufficient moisture, the probe resistance will be below the calibrated level ofconductivity and the current will travel along the path to light the green LED.

Parts Needed for Assembly1 Probe2 different colored Jumbo LEDs (preferably red and green)1 9V Snap1 IC Socket Chip (gate)1 Pushbutton Switch1 100k Trimmer Resistor4 Resistors

1 22K ohm1 100 ohm2 200 ohm

3 Pieces of Wire1 pair and one single

20-24 Gauge Stranded1 Circuit Board (see Figure 4)1 Solder Gun with Rosin Core Solder

Assembly Directions1. Use the given Resistor Color Code to determine the value of the resistors. (See

Figure 2)2. Install IC Socket. (Observe locating mark on IC and cathode side on LEDs

when installing these components. See Figure 1 and 6)3. Install resistors per color code. (see Figure 2)4. Install 100k Trimmer Resistor with face out (See Figure 1)5. Install Pushbutton Switch6. Install Battery Snap7. Install single wire to one of the connections of the pushbutton and the other

end to the correct location of the circuit board.8. Solder red wire (+) of battery snap to the other pushbutton connector.9. Using your paired wire, solder one wire to one side of the probe and the other

end to the correct input on the circuit board. Solder the second wire to theother side of the probe and the other end to its correct input of the circuitboard.

Main Components and Their Function


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• Quad 2 Input Gate — Sends an electrical message to the different gateswhether enough moisture or not enough moisture.

• Control Trimmer Resistor — Adjust to the level desired by operator totest for desired moisture level of soil. Like a dimmer switch, it changesthe resistance of a resistor. (This is the Variable.)

• LEDs — Able to convert electrons directly into photons (visible light).Since the LEDs have PN junctions (semiconductors) the current that flowsthrough them is limited by the resistors. The electrons from one half ofthe semiconductor jump to the holes of the other half of thesemiconductor. This is because the current forces them there. They areonly able to jump when the current is on and they return to their startingposition when the current is switched off.

Red LED - most resistantGreen LED — least resistant

• Resistors — Controls the amount of current that flows through the monitor.R1 limits the current that flows from the probe into the gate.

This is a protection device so the device won t short circuitwhen placed in very wet soil.

R2 and R3 controls the amount of current into the red and greenLEDs.

R4 limits current from the battery to the gate.• Circuit Board — Sends the current from the 9V battery throughout to the

different components. (Makes the connections.)

ApplicationsCalibrated levels of water per color code and percentages of water.

Water (ml) Dot Color % of Water in Soil0ml (Control)5ml Dark Blue 10%5-7.5ml Light Blue 15%7.5-10ml Green 20%12ml Yellow 25%15ml Orange 30%

• ~20 grams of soil was placed in each cup• The Red Dot represents the levels of 35ml of water or higher.

Depending on time allotted for lab, students may be allowed to calibrate their soilmonitors by setting up 6 or more different cups with 20 grams of soil and addingdifferent ml amounts of water, or calibrate it by the above settings.


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Student Pages

You will be given components and assembly directions1) Instructions

A) Make the CircuitB) Test the preset soil sample your teacher has provided and

check to see if your reading is correctC) If reading is correct, test three plants throughout the room or

outside and record red vs. greenD) Design an inquiry lab using different moisture levels in the

soil to calibrate your device2) Illustrations

See the figures that accompany this sheet(Plant Soil Monitor Figures)

3) Guided QuestionsA) Briefly outline the path of the charge in the circuitB) What determines if the Red or Green LED is illuminated?C) Based on the information you found, give the approximate

moisture in 3 different soil settings

Omnitron Electronics for Kits1-800-379-664

Strobe Light $6.95Digital Chirper $6.95Musical Christmas Tree $6.95Burglar Alarm (for car, house, room, closet, etc.) $4.95Lie Detector Kit $8.95Voice Changer $13.95Tingler Kit $9.95Electronic Stapler Kit $9.95Basic Electronic Component Course (over 50 parts) $11.9533-in-1 electronics lab $22.95Solar Race Car Kit $26.95


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