Page 1. WARNING: ! CHOKING HAZARD - Small parts, wire. Not for children under 4 years. PicoTurbine Windmill Direct Current Experiments Instructions, Teacher’s Guide, and Technical Notes An easy to build project for adults and children grade 9 and above. Explains alternating current and direct current concepts, including rectification, voltage, and frequency. This set of plans and the associated kit are an add on to the PicoTurbine project. Page 2. THESE PLANS ARE PRESENTED IN “AS IS” CONDITION. BY USING THESE PLANS YOU HOLD PICOTURBINE.COM, XIBOKK RESEARCH, AND ALL MEMBERS, INVESTORS, EMPLOYEES, AND OWNERS OF THOSE ORGANIZATIONS HARMLESS FROM ANY DAMAGES ARISING FROM THE USE OF THESE PLANS OR THE RESULTING MACHINES. IN NO CASE SHALL PICOTURBINE.COM OR XIBOKK RESEARCH BE LIABLE FOR ANY INCIDENTAL DAMAGES. THESE PLANS ARE NOT WARRENTEED FOR FITNESS FOR ANY PARTICULAR PURPOSE. Revision 1.0D, August, 1999 www.picoturbine.com Support PicoTurbine.com! If you have purchased this document as a part of a PicoTurbine.com kit, we appreciate your support! If you have downloaded this document as a free plan, we hope you enjoy it, and ask that you patronize PicoTurbine.com in the future so we can keep financing new projects. We have a complete line of Renewable Energy books, projects, and kits that are expanding every day. Stop by the web site and buy something! Tell your friends about us! Suggest our projects for youth groups, Scouting Groups, YMCA or similar organizations, classrooms and home schools. The proceeds will be used to support more fun renewable energy projects and kits at PicoTurbine.com. Thanks and have fun! Copyright � � 1999 PicoTurbine.com. All rights reserved. PicoTurbine.com is a wholly owned subsidiary of Xibokk Research. Page 3. CONTENTS PART 1: INSTRUCTIONS FOR BUILDING PROJECTS .................................................................. 4 A NOTE ON PICOTURBINE VERSIONS........................................................................................... 4 BEFORE YOU BUILD THE CIRCUITS.............................................................................................. 4 Step 1: Check Your Materials............................................................................................................ 4 Step 2: IMPORTANT: Review Safety Rules........................................................................................ 5 MOTIVATION ........................................................................................................................................ 5 TERMINOLOGY AND PARTS.................................................................................................................... 6 The Diode (or Rectifier).................................................................................................................... 6 The Capacitor................................................................................................................................... 6 The Light Emitting Diode (LED) ....................................................................................................... 7 The Piezo Buzzer .............................................................................................................................. 7 The Solderless Breadboard ............................................................................................................... 8 Connecting the PicoTurbine Alternator to the Breadboard Using Jumper Wires ................................ 8 TROUBLE SHOOTING ............................................................................................................................. 9 CIRCUIT 1: A SIMPLE HALF WAVE RECTIFIER ..................................................................................... 9 Building the Circuit ........................................................................................................................ 10 Experiments With the Half Wave Rectifier....................................................................................... 10 CIRCUIT 2: SMOOTHING DC RIPPLE USING CAPACITORS.................................................................... 10 Building the Circuit ........................................................................................................................ 11 Experiments With the Smoothed Half Wave Rectifier ....................................................................... 11 CIRCUIT 3: A FULL WAVE RECTIFIER................................................................................................ 11 Building the Circuit ........................................................................................................................ 11 Experiments with the Full Wave Rectifier........................................................................................ 12 CIRCUIT 4: A VOLTAGE DOUBLING RECTIFIER .................................................................................. 12 Building the Circuit ........................................................................................................................ 12 Experiments with the Doubling Rectifier ......................................................................................... 13 PART 2: TEACHER’S GUIDE ........................................................................................................... 14 CONCEPTS REQUIRED BEFORE BUILDING THE CIRCUITS ....................................................................... 14 REASONS FOR ALTERNATING AND DIRECT CURRENT............................................................................ 14 PART 3: TECHNICAL NOTES.......................................................................................................... 16 INTRODUCTION ................................................................................................................................... 16 DIODE LOSSES .................................................................................................................................... 16 EFFICIENCY OF A RECTIFIER ................................................................................................................ 16 VALUES OF CAPACITOR NEEDED FOR SMOOTHING................................................................................ 16 Page 4. PART 1: Instructions for Building Projects This document will show you how to build circuits that will take the output of a PicoTurbine wind turbine and convert it into a DC voltage. These instructions assume you already have built a PicoTurbine miniature windmill (see picture below). There are four different circuits explained in this document for converting PicoTurbine’s AC output to DC. Each one requires only 10 to 15 minutes to create using a solderless breadboard which is included in the kit. PicoTurbine: normally produces alternating current, but with this add-on kit can be made to produce direct current. A NOTE ON PICOTURBINE VERSIONS The version 1.0 series of PicoTurbine produces about 1 to 1.5 volts at about 200 mA, while the version 1.1 series produces about 2 to 2.5 volts at about 30 mA. These experiments should work for both versions, but the text below is written such that it refers to voltages produced by the 1.1 version of PicoTurbine. BEFORE YOU BUILD THE CIRCUITS Step 1: Check Your Materials The following materials are supplied with your PicoTurbine-DC kit. If you did not purchase a kit but are ♦ A small solderless breadboard and several pieces of 22 gauge prestripped hookup wire. ♦ Four germanium diodes rated at 100 milliAmps or more continuous and peak inverse voltage (PIV) of at least 6 volts. ♦ Two electrolytic capacitors rated 47 microFarads and at least 6 volts. ♦ One piezo-electric buzzer rated at 2-12 volts DC, not requiring an external driver circuit. Not all piezo buzzers will work, the one used here is Radio Shack part 273065. ♦ One bicolor LED with two leads. It is also helpful to have the following tools, but not entirely necessary: Page 5. ♦ A digital multimeter that can measure AC/DC millivolts is useful for displaying the exact voltage created. ♦ A small set of needle nose pliers can make inserting and removing jumper wires from the breadboard much easier. ♦ If you have a really well equipped lab and happen to have an oscilloscope, this is a great way to see the actual voltage waves. Oscilloscopes are quite expensive, however, so this kit was designed so you can “hear” the waves using a piezo buzzer placed in different ways. Still, nothing is quite like looking at the patterns on a ‘scope if you happen to have one or can borrow one from an electronics professional or enthusiast. Step 2: IMPORTANT: Review Safety Rules PicoTurbine-DC is not a dangerous project to build, but as with any construction project certain safety rules must be followed. Most of these rules are just plain common sense. Be sure to review these rules with children if you are building this project as part of an educational curriculum. ♦ The electronic components used in this kit are only capable of handling the small amounts of current and voltage produced by PicoTurbine. UNDER NO CIRCUMSTANCES SHOULD AC CURRENT FROM A WALL OUTLET BE ATTACHED TO ANY OF THESE PARTS. HIGH VOLTAGES AND CURRENTS FOUND IN STANDARD WALL OUTLETS WILL CAUSE EXPLOSIONS, BURNS, FIRE, AND SHOCK HAZARDS, INCLUDING POSSIBLE DEATH. ♦ Adult supervision is required for this project. ♦ This project is not recommended for children under 11 years old. ♦ Children must be supervised when working with scissors and other sharp parts to avoid cutting injuries. ♦ Children under 4 years old should never work with wire or small parts because they represent strangulation and choking hazards. Keep the kit parts out of the reach of small children. ♦ PicoTurbine generates low levels of electricity (under 3 volts) that are generally considered safe and are of the same order as produced by batteries used in toys or radios. But, to avoid shock hazard never work with electricity of any level when your hands or feet are wet. ♦ Persons wearing pacemakers should not handle magnets such as those found in the PicoTurbine alternator. Motivation PicoTurbine produces electricity using an alternator. The word alternator is used because such a device produces alternating current, or AC for short. Alternating current constantly varies between a positive and negative voltage, usually in a sine wave pattern (see figure below). +V -V Page 6. Alternating current can be used directly by many devices, such as heating elements for an electric stove or an electric light bulb. However, many devices require direct current (DC), which does not vary but remains at a steady voltage. Luckily, it is possible to convert AC to DC. The process of converting AC to DC is called rectification, and there are several different ways to do it. This kit allows you to build several different kinds of rectification circuit. This section will give you diagrams and figures to use the kit materials to do this easily. The Teacher’s Guide and Technical Notes sections of this document go further into the theory of electrical power conditioning. Terminology and Parts To understand how to build these circuits, a little background on how the parts are named and what they do is in order. The table below shows some of the parts in the kits, displays the electrical symbol for each one, and explains the function of the part. The Diode (or Rectifier) Symbol: Picture: A diode (also called a rectifier) only allows current to go in one direction. Current flowing in the opposite direction is stopped. Think of a diode as a one-way valve for electricity. Diodes are rated as to how much current they can handle, and the maximum amount of reverse voltage they can withstand (this is called the Peak Inverse Voltage, or PIV). The black band around one end of the diode (the left on the picture above) shows the positive voltage side. In a circuit diagram the convention is that electricity flows from positive to negative. So, electricity could flow from the unmarked to the marked direction, while it would be stopped from the marked to the unmarked direction. The symbol for a diode shows this as an arrow. The Capacitor Symbol: Picture: A capacitor can store electrical charge. Think of a capacitor as a kind of very small rechargeable battery that can only hold a small amount of charge. Some diodes are polarized such that one side should always be positive, others are not polarized. The symbol for a polarized capacitor shows a + sign on the positive side. Page 7. The actual capacitor typically has a stripe or a minus sign on the side of the negative lead. In the picture above, this is a lighter color stripe on the right. Sometimes this stripe has a “-“ sign imprinted within it. The Light Emitting Diode (LED) Symbol: Picture: An LED is a diode, and only allows electricity to pass in one direction. The symbol for an LED is the same as for the regular diode, but two small arrows indicate that light is emitted. The actual LED has one short lead and one longer lead. The shorter lead is the negative side. When current flows in the correct direction, this has the side effect of producing light. LEDs are very efficient at converting electricity to light and can operate at very low currents compared to equivalent incandescent lamp light. The LED included in the kit is a special bi-directional LED. It is actually two LED’s connected back-to- back such that when electricity flows in one direction it lights up red and in the other direction green. In a circuit diagram this is usually shown as two diodes in parallel, perhaps with labels indicating the color of each one, such as: The Piezo Buzzer Symbol: Picture: A piezo buzzer uses the piezo electric effect to convert electricity into motion of a thin slice of crystal material. With enough voltage, the piezo buzzer will make an audible sound. The experiments in this plan use a piezo buzzer because it makes it easy to “hear” that a current is alternating or not, and even how high the voltage is (by how high the frequency sounds). There are various kinds of piezo buzzers. Some require external circuitry to drive them. The one included in your kit requires no external driver and can take a wide range of DC voltages. Even though it is rated at red green + - Page 8. 12 volts, it will produce a chirping sound that is quite easy to hear even at the 2 volt level of the little PicoTurbine. The leads are marked on the bottom as to which is positive and which negative. The Solderless Breadboard Picture: The solderless breadboard allows you to quickly set up circuits without having to make solder connections. This is faster and much safer in a classroom setting. The breadboard is marked so that rows have a number and columns have a letter. This kit will tell you to make connections using a combination of a letter and number. For example, “place a diode from A3 to A5”. This would mean place the unmarked side of the diode in A3 on the breadboard and the marked side in the A5 hole. As you can see from the picture above, there is a row marked “X” at the top and another marked “Y” at the bottom. All of the “X” holes are connected to each other. All of the “Y” holes are connected to each other as well. These are called “bus bars” and they are usually used to carry the negative (or ground) and positive voltages from the battery. They run along the length of the whole breadboard to make it easy to make ground and positive voltage connections wherever necessary. The other rows work a little differently. Each column is divided into the upper letters (A through E) and the lower letters (F through J). Each column is connected in two sections, one for the upper and one for the lower. For example, A1, B1, C1, D1, and E1 are all connected to each other. Also, F1, G1, H1, I1, and J1 are connected to each other. These groupings are also true for all the other columns, column 2, column 3, etc. The reason for this layout is to make it easy to insert a DIP Integrated Circuit (IC) chip and then allow multiple connections to each pin of the chip. This document provides recommended layouts for each circuit, but many alternative layouts are possible. Keep in mind how the different parts of the breadboard are connected internally and try to visualize how the circuits shown in the schematic diagrams match to the breadboard layouts given. To insert components in the breadboard, simply bend the wire leads as necessary to reach the correct pin holes, then insert the pins approximately a quarter inch. Make sure the connections are inserted completely and firmly. Use caution when removing components so you do not damage them. Simply apply a stead pulling pressure until the leads detach. Sometimes the short jumper wires you will use to make connections will break off inside the breadboard hole. If this happens, you may need to use needle nose pliers to remove such broken wires. If you cannot remove such a wire, simply use alternative holes in the breadboard for the remaining experiments. Connecting the PicoTurbine Alternator to the Breadboard Using Jumper Wires When connecting the PicoTurbine alternator to the breadboard, it is helpful to first connect the alternator wires to two of the short jumper wires. Twist at least a full inch of stripped alternator wire to one end of a jumper, then pinch the bare jumper wire down against the insulation. Do this for each of the two alternator wires. Now, it is a simple matter to insert and remove the other end of each short jumper. The PicoTurbine alternator wires are a little too thin to make a good connection directly to the breadboard. Page 9. Trouble Shooting If you build one of these circuits and it fails to function as described in the text, follow these steps to solve the problem: 1. Check the connections. Double check the list of connections to make sure all the components are in the correct positions. It is common to forget a connection or miss the correct pin hole by one slot. The piezo buzzer is especially vulnerable to this because you have to carefully look from the side while inserting it to make sure its PC mount leads are going into the correct holes. 2. Check diode directions. Diodes only work in one direction, so it is critical that the black band on one side be in the proper pin hole. The instructions below always say which hole should receive the “banded” side of the diode. 3. Check piezo buzzer direction. The piezo buzzer will only work if its terminals are properly positioned. They are clearly marked “+” and “-“. The directions below will indicate which hole receives the “+” terminal. 4. Make sure all connections are tight. All connections must be nice and tight. At a minimum about ¼ inch of lead should be in the hole. You should feel the lead somewhat “snap” into the hole. A very slight pulling pressure should not bring the wire lead back out, it should take a bit of effort to remove in which you feel some friction. If none of the above suggestions work, you may have a defective part. You can in some cases check this. You can check the piezo buzzer by simply connecting it to two 1.5 volt batteries in series (making sure the + lead goes to the + terminal of the battery). The buzzer should go off easily at 3 volts. You can check the LED by directly connecting it to your PicoTurbine and giving a good spin. It should flash red and green. You can check a diode in circuits that only require 2 diodes by replacing them with the other 2 diodes. If the circuit works with one diode and not another, you may have a defective or burned-out diode. If all else fails, send email to