Fun Projects for the Experimenter - volume 2 E-Book

Newton C. Braga

• Herausgeber: Editora NCB
• Kategorie: Wissenschaft und neue Technologien
• Serie: Fun Projects for the Experimenter
• Sprache: Englisch

Seitenzahl: 204

Veröffentlichungsjahr: 2015

Beschreibung

During more than 30 years, as a collaborator with American, European and Latin American electronics magazines (*), has published a large assortment of practical circuits using common parts. In 1999 he included the first selection in a volume published by Prompt Publications in USA. The idea was to proceed with the series, publishing many volumes more. But, Prompt closed his activities and the idea was forgotten although the first volume became a best seller. Now with his own publishing house (NCB Publications) the author returned with the idea of make many volumes more of the series. So, the second volume is here proceeding with the same idea: give simple projects to the experimenters who want learn electronics using common parts and with no need of special knowledge about electronics. So, as in the first volume, many of the projects collected by the author are included in this volume, most of which you can build in one evening. The projects range from fun types through practical types to amusement types. Of course, there are other devices that can be used to teach you something about circuits and components. An important feature of theses projects are the ideas to Explore, intended for students looking for projects in science or to use in practical research. This ideal can be complemented by our book Science Fair and Technology Education Projects, also published in English by the author. We can consider this book as a source book of the easiest and fun-to-make of hundreds of projects created and published by the author during his life. (see more about Newton C. Braga in "about the author" in his site).

Leseprobe

Newton C. Braga

FUN PROJECTS FOR THE EXPERIMENTER

volume 2

Institute Newton C. Braga

São Paulo - 2015

Institute NCB

www.newtoncbraga.com

[email protected]

FUN PROJECTS FOR THE EXPERIMENTER - volume 2Author: Newton C. BragaSão Paulo - Brasil - 2014

key-words: Electronic

Copyright by

INTITUTO NEWTON C BRAGA.

1ª edição

All rights reserved. No part of this book shall be reproduced, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without written permission from the publisher. No patent liability is assumed with taken in the preparation of this book, the author, the publisher or saller assume no responsibility for erros or omissions. Neither is any liability assumed for damages resulting from the use of information containes hereing.

Officer responsible: Newton C. Braga

Design and Coordination: Renato Paiotti

Conteúdo

MATCHBOX RADIO (E)

HEAT DETECTOR (E, P)

ENERGY SNIFFER(E)

TWO-TRANSISTOR AM RADIO

MINI-INTERCOM(E)

MAGNETIZER (E)

AUDIO BIOFEEDBACK(E)

VISUAL BIOFEEDBACK (E)

DIGITAL VOLTMETER(P)

INFRA-RED DETECTOR (E)

LIGHT-ACTIVATED REMOTE SWITCH (P)

MAGIC LAMP(E)

LIGHT-BEAM TELEGRAPH (E)

MYSTERIOUS MOTION(E)

MAD TEST-YOUR-NERVES (E)

EXPERIMENTAL INVERTER (E)

TOUCH SWITCH (P)

SUPER-SIREN (P)

SOLAR TRANSMITTER (E)

DIGITAL DIMMER(P)

ELECTRONIC SCARECROW (E/P)

SIGNAL TRACER (P)

GUN MACHINE (E)

LIGHT CONTROLLED OSCILLATOR (E)

LIGHT ACTIVATED OSCILLATOR (E)

DARK ACTIVATED RELAY (P/E)

INSECT REPELLENT (P/E)

WIRELESS FM-ALARM (E/P)

CW-SW TRANSMITTER(E)

SIMPLE STROBOLIGHT(E/P)

ULTRA-SONIC TRANSMITTER(E)

BAT EAR (E)

ELECTRONIC POTENTIOMETER(P)

MINI POWER-SUPPLY (P)

NAIL OSCILLATOR (E)

CAPACITOR TESTER (P)

ELECTROMAGNET(E)

DARLINGTON PROBE(P)

MICRO-ALARM(E/P)

MONOCHROMATIC LIGHT SOURCE (E)

BATTERY CHARGER (P)

SHOCK MACHINE (E)

Project 44 - REMOTE POSITION INDICATOR (E)

Project 45 - PROBE AMPLIFIER (P)

WHO IS THE FASTEST(P/E)

EMERGENCY LIGHT (P)

TOUCHED CONTROLLED MOTOR (E)

MANUAL SIREN (P)

0 to 9 V Power Supply (P)

Preface

During more than 30 years, as a collaborator with American, European and Latin American electronics magazines (*), the author has published a large assortment of practical circuits using common parts.

In 1999 he included the first selecion in a volume published by Prompt Publications in USA. The idea was to proceed with the seris, publishing many volumes more.

But, Prompt closed his activities and the idea was forgotten altough the first volume became a best seller.

Now with his own publishing house (NCB Publications) the author returned with the idea of make many volumes more of the series. So, the second volume is here proceeding with the same idea: give simple projects to the experimenters who want learn electronics using common parts and with no need of special knowledge about electronics.

So, as in the first volume, many of the projects collected by the autor are included in this volume, most of which you can build in one evening (*)

(*) many of the projects you can access in the site in Portuguese – www.newtoncbraga.com.br and in English – www.newtoncbraga.com in the section Mini Projetos (Mini Projects). Mini-Projects is the title of a column publsihed by the author during several years in a Brazilian Electronics Magazine and now included in his sites in Portuguese and English.

The projects range from fun types through practical types to amusement types. Of course, there are other devices that can be used to teach you something about circuits and components.

An important feature of thses projects are the Ideas to Explore, intended for students looking for projects in sciente or to use in practical research. This ideal can be complemented by our book Science Fair and Technology Education Projects, also published in English by the autor.

We can consider this book as a source book of the easiest and fun-to-make of hundreds of projects created and published by the author during his life (see more about Newton C. Braga in “about the author” in his site).

But, as the projects are in a wide range of types, we should separate the electronics experimenters in two groups: the ones who want to improve or expand some other area of their electronics interest, such as computers, radio, instruentation, audio, security and even mechatronics; and the ones who want to learn something about electronic circuits and devices or want new ideas to use in science projects.

Most of the projects described herein can be stand-alone as indivudual acessories; weherever possible the circuits have been designed so that they can be ganged with one or more other projects. For exemple, many projects of audio effects or generators can be ganged with audio amplifiers or high-power output stages.

All the projects are simple, with few low-cost components that can be made in one evening of work.

To make it easy for the reader to choose the projects we added codes after each title to indicate the kind of experimenter for whom they are intended: the code “P” (Practical) indicates a project built to practical use. The code “E” (Experimental) indicates that the project is intended for the experimenter to teach something about circuits or devices.

Or course, you can also find projects with both codes (E and P) which can ether be ounted to teach something or/and be used for a practical end.

The presentations of the projects are practical. Electronics components are listed with each circuit diagram. But secondary parts such as sockets, chassis, enclosures, miscellaneous hardware and so on, are not specified, since the reader is free to choose these non-critical items according to his preferences and demands.

The manner in which the circuits work and can be modified is explained in practical terms so the reader can acquire some knouledge of practical electronics as he progresses through the book.

Although many of the projects we enjoyed constructing as they are described here, you may think or possible modifications. We just recommend that you go ahead and modify the circuits to your personal ends. There is a wide latitude in circuit modifications and most of them will be of value to the experimenter who wants to see how things work, even though each project’s primary intend is for the builder who desires a functional item of equipment as the result of his work.

As the book includes easy-to-build projects, the author hopes it will help you to learn many of the fundamentals of electronics in a easy and fun way, and, if you’re a student provide a source for school projects.

Newton C. Braga

Volume 1 - Front-Cover – Published by Prompt Publications in 1999.

MATCHBOX RADIO (E)

This small crystal set can be housed in a matchbox and is abble to tune the local strong AM stations using as antenna a long wire.

As the circuit has no active components as transistors or valves to increase the sinal strenght only an earphone can be excited as final transducer. The power isn’t enough to drive a loudspeaker and hear is weak even tunning strong stations.

The antenna should be as long as possible to intercept a great amount of radio waves’ energy and gives a reasonable output power to the earphone. We recommend an antenna with lenghts no less than 20 feet to best results.

Ground connection is very important to increase the circuit performance. The ground connection can be done using the earth pole or neutral in the power supply AC line, but this requires special care to avoid dangerous shock hazards and it is not the recommended away to use your radio.

Without the need of specialized assistance we recommend as ground connection a metal tubular or plate piece introduced deep into the ground. A 10 x 10 inches plate or a 30 inches long bar can be used for this task. Another away to get a ground connection is to clip the alligator clip ito any large metal piece around you as a door or window metal square.

You can use this receiver to show as a radio that doesn’t need batteries or other power-supply can be made and also say that this kind of set was the only one that exists at your grandfather’s time. You can also explain that this radio function as the antique crystal sets or galena radios invented in the last century.

Of course, many of the used components are modern as ceramic capacitors, germanium diodes and ferrite rods and also the earphone and they were invented only some tens of years after the original crystal set that used a galena crystal to detect radio signals.

Figure 1 shows the squematic diagram of the matchbox radio using modern components.

Figure 1 – Schematic diagram of the radio

The circuit should fit into a small matchbox or plastic box, with a hole drilled in the side to acommodate the ferrite core as shown in figure 2.

Figure 2- Mounting usin a small box like a matchbox

L1 is a antenna tuning coil wound on a cardboard tube with a internal ferrite rod and is made winding 80 to 100 turns of 28 AWG enameled wire.

The ferrite rod has a diameter between 0,5 and 1 cm and should slide into the tube as tunning is made adjusting its position.

All capacitor are ceramic disc types. The same circuit will work as well, or even better, using nearly any RF germanium diode. Old germanium transistor can also be wired as diodes. To connect a germanium transistor as a detector diode you only have to ignore the collector lead.

The crystal earphone is recommended but any magnetic high impedance earphone with impedances between 2,000 and 10,000 ohm can also be used. Low impedance earphones, as used in walkmans and small transistorized radios will not operate in this project. They are not sensitive enough to operate from the low power signals sourced by this radio output.

Using the set: connect the alligator clips to the antenna and ground. Slide the ferrite rod into the antenna tube until you tune a station.

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Parts List - Matchbox Radio

D1 - 1N34 or equivalent - any germanium diode

L1 - Antenna coil - see text

C1 - 47 pF - ceramic capacitor

C2 - 220 pF - ceramic capacitor

C3 - 1,000 pF - ceramic capacitor

XTAL - Crystal earphone or high impedance magnetic phone

A. G - Alligators clips

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IDEAS TO EXPLORE

a) To learn more about the circuit and components or to get better performance:

- Use an audio amplifier connected to the output of this radio to get better performance. The probe amplifier descibed in this book can be used to increase the audio output.

- Wire the antena alligator clip to your TV antenna connector. What can you expect making these connections? Will the radio function?

- If there is a very strong radio station near you can try to wire to the output a small transistor audio output transformer and a loudspeaker.

b) Science projects:

- Explain how a crystal set operates.

- What is a galena crystal and why it can be used as a detector?

- What is the difference between a galena crystal and common germanium or silicon diodes?

- Explain how this set can source electric energy to the earphone to be converted in sound and from where comes this energy.

- Explain why a low impedance loudspeaker can’t be excited by the signals found in this radio output.

HEAT DETECTOR (E, P)

Heat loses in electronic appliances or at your home can be easily detected using this simple device. You can also use this circuit to detect temperature variations in experiments involving biology, chemistry or physics.

Critical points in a project as hot resistors, transistor or other components who convert electrical power into heat and cause many problems can be also detected using this circuit.

But the particular attraction in this circuit is that temperature sensing device (the diode) can be quite remote from the indicating device (the ammeter). Thus the sensor can be placed outdoors to detect outside temperature changes, coupled by two thin insulated wires to the detector circuit indoors.

As the amount of current flowing through a circuit depends upon the amount of voltage applied and also the amount of resistance in the circuit, any point with anormal resistance will produce heat enough to cause damages to the components.

The proposed circuit shows when the temperature in any point of a circuit rises to values high enough to manace components.

The circuit can also be used at home to detect heat loses. Invisible holes or apertures in windows, doors or in the floor causes heat loses that increases the amount of power necessary to sustain the desired indoor temperature in any ambient.

The circuit uses as a passive temperature transducer a common silicon diode. As the amount of current through a diode reverse biased depends upon the temperature of the junction, this kind of component can be used as a sensitive detector to temperature variations.

The amount of current through the diode is very low so we need amplification. The current is amplified by a transistor driving a microammeter. P1 adjusts the zero point to the center of the scale, as the needle has to oscilate right and left, according the temperature goes up and down.

Figure 1 shows the schematic diagram of the heat detector.

Figure 2 – Schemtaic diagram of the detector

Components are placed on a terminal strip used as chassi is shown at figure 2.

Figure 2 – Mounting using a terminal strip

The sensor, any common silicon diode, is mounted at the end of a pen tube.

Take care with the position of the diode since it is a polarized component as the battery and the transistor. Depending on the application, you can protect the diode with an epoxi cover.

Any microammeter with current ranges from 100 to 500 uA can be used in this project. You can find ammeters in non-functioning old amplifiers were they are used as VU-meters.

Now you are going to test the circuit: adjust P1 to have a center scale position of the needle in M1.

Put the sensor between your fingers and wait about 40 or 50 seconds to achieve the termal equilibrium. The heat of your body will be detected and you will see the ammeter needle moviment indicates the temperature rise.

Don’t touch the terminals of the diode as this will cause modification of the resistance with a false indication temperature variation (protect the diode with an epoxi coat if necessary).

Using the detector: put the sensor near (don’t touch) the place where you want to detect heat variations and wait about 40 seconds or more to allow the sensor to change its own temperature according the ambient and observe the ammeter needle.

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Parts List - Heat Detector

Q1 - general purpose NPN silicon transistor

D1 - 1N914 or equivalent - general purpose silicon diode

R1 - 22,000 ohm, 1/4-watt, 5% - resistor

R2 - 1,000 ohm, 1/4-watt, 5% - resistor

P1 - 47,000 ohm - potentiometer

S1 - SPST - slide or toggle switch

B1 - 9 V - battery

M1 - 0 - 200 uA - microammeter - see text

_________________________________________________________________________________________________________

IDEAS TO EXPLORE

a) To learn more about circut and devices an some questions:

- Why can’t be used a foward polarized diode as sensor in this experiment?

- Can you explain how the current flow through the diode alters with the temperature?

- Replace Q1 by a Darlington transistor as the BC517 and get much more sensivity to the circuit.

- Replace D1 by a NTC or a PTC (between 20,000 and 100,000 ohm and increase the sensivity of the heat detector. NTCs and PTCs or Temperature Sensitive Resistors are components in which the actual resistance offered by the device in a circuit depends on its temperature. The NTCs have a negative temperature coefficient. This means that resistance decreases as temperature increases. PTCs, on the other hand, have a positive temperature coefficient, and operate in the opposite manner - resistance increases as the temperature increases. Both types can be experimentd in this project. Wire between the base and emitter of Q1 a 10,000 ohm trimmer potentiomer to adjust the polarization according the sensor new characteristics.

b) Science and different uses for the circuit:

- Endothermic or exothermic experiments in chemistry can be easily monitored with this circuit. You can easily measure heats of reaction making an experiental calorimeter and using this circuit to detect temperature changes. A simple calorimeter for reactions in aqueous solution can be constructed from a Styrofoam coffee cup. For hot or nonaquous solution reactions you can use a thermos bottle with a wide mouth.

- Operation of heaters, refrigeration systems in laboratory experiements can be monitored placing the sensor far from the circuit.

- Variations of temperature of living beens and ambients in several kind of biological experiments can be monitored with this circuit.

- Experimentation in thermometry and thermology can programmed using this circuit.

- You can use this circuit as a thermometer but the microammeter scale can only be calculated in terms of equivalent temperatures by direct comparison with another thermometer at different temperatures. Adjusting P1 you can set the zero temperature at the zero scale reading on the meter. But remember that temperature measurement scales (Fahrenheit and Celsius) are linear systems as the diode is not a linear device over a wide range of temperatures.

ENERGY SNIFFER(E)

Many important research laboratories all over the world are working hard trying to find new alternative sources of electric energy.

You can also make some interesting experiments in this field using this electric energy sniffer. Home-made electric experimental cells can be tested using this project that will tell you if your new discovery is good enough to power some small electric appliance or device as LEDs, small DC-motors, transistor radios, etc.

An excellent work to demonstrations in your school can also be performed with this energy detector and some suggested simple alternative sources of electric energy or alternative cells.

The project consists in a simple home-made galvanometer i.e. an instrument that can be used to detect current flow through a circuit.

It is very easy to explain how it works: when electric power is produced it appears as a voltage between the poles of a cell and this causes a current flow in any circuit wired to these poles. If the energy detector is placed in series, the current flow through the galvanometer’s coil will produce a magnetic field that acts on the needle (a razor blade).

The razor blade tends to place its position according the generated field force lines making a moviment that can be easily observed. That means that any razor blade moviment is an indication of current flow and also energy beeing produced by the cell.

The energy sniffer can detect current flows as low as few microamperes and is suitable to be used with experimental cells with voltage ranges between 0.2 and 2.0 volts.

Figure 1 shows how the energy sniffer is built with a razor blade

Figure 1 – Using a razor blade

Figure 2 shows how the energy sniffer is built using a compass and two coils.

Figure 2 – How the energy sniffer is built

Figure 3 shows the energy sniffer wired to a common 1.5 V cell and a 100 ohm resistor to a test of sensivity.

Figure 3 – Testing and detecting the energy of a cell

The razor blade is placed in the center of the coil by a short flexible cotton wire allowing the moviments without any difficult.

The coil is formed by 20 to 100 turns of any AWG wire in a 4 x 4 inches cardboard or plastic form. A terminal strip is used to wire the external circuits.

A simple electric cell can be constructed as follows:

Obtain a jar to be used for the battery case. Fill it with water and salt or water and any acid fruit juice as lemons, lime, grapefruit, etc. In the laboratory, with careful, you can use a low concentration sulphur acid solution.

As a general rule the higher the acid content the better the battery it will make.

Bend two metal plates (one should be a copper plate and the other a aluminium, tin or zinc plate) and insert them into the jar. The copper plate is the positive pole when the other plate is made with any suggested metal. It is very important that no part of the two plates touch. If they do touch the cell will be shorted and no external voltage will be detected.

The cell is wired to the external circuit using wires with alligator clips.

Obs: A piece of 1 foot of heavy copper wire without insulation, bent to increase the area into the solution can replace the copper plate in this experiment.

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Parts List - Energy Sniffer

L1 - Coil - see text

R1 - 100 ohm, 1/4-watt, 5% - resistor - optional to test

B1 - 1,5 V - AA cell - optional to test

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IDEAS TO EXPLORE

a) To learn more about the circuit or to increase performance:

- How the amplitude of the blade moviment indicates the amount of energy produced by the cell? Explain how this circuit works.

- Use a 1,5 V AA cell and a 100,000 ohm potentiometer and a multimeter (all wired in series) to measure the sensivity of your energy sniffer.

- Who was Oesterd and how this project uses his discovery?

- Does the earth magnetic field have any influence in this experiment? Explain why?

b) Science and different applications for the project:

- An allegoric rythmic pendulum can be performed wiring the circuit with a 100 ohm series resistor to the output of an audio amplifier. The razor blade will “dance” according the music.

- A visual experimental telegraph can be mounted using this sniffer as receiver and a cell and a morse key as transmiter.

TWO-TRANSISTOR AM RADIO

Direct amplification AM experimental radios are very interesting projects for beginners because they use only few components and don’t need special instruments to make adjustments.

Here we describe a receiver which uses only two transistor as active elements and can tune local strong AM stations using as antenna only a piece of wire.

The antenna should be a common insulated wire 6 to 10 feet long placed on the floor or high in the walls.

Signal amplification is made by two complementary transistors with an output power high enough to drive a small loudspeaker.

The radio can be powered from two or four AA-cells or, if you prefer, from a power-supply plugged to the AC power line.

Since the circuit is not selective and sensitive as a commercial radio it is recommended only as an experimental project to demonstrations or to learn how to make electronics projects and how radio receivers work.

How it works: L2 and CV forms the resonant circuit that determines the frequency of the station to be received.

The signal in the output of the resonant circuit is detected by D1 and the audio signal that results in this process is applied, via C1, to the base of Q1.

C2 offer a path to ground to the high frquency component of the detected signal.

Q1 and Q2 are wired as a directed coupled amplifier with the polarization for better performance adjusted by P1.

L1 is formed by 20 + 80 turns of 26 to 30 AWG wire on a ferrite rod. L1 is formed bu 5 turns of the same wire on the same ferrite rod. Any ferrite rod with lenghts between 4 and 12 inches can be used. You can find a ferrite rod suitable for this project in any old non-functioning transistor radio.