1. 1 SPIRIT Silicon Prairie Initiative on Robotics in Information Technology Soldering and Building a Battery Tester

2. 2 SPIRIT Build Your Skills  OBJECTIVES:  Learn to Solder  Learn how the circuit components work in a simple circuit used to test a battery.  Gain exposure to the fundamental law of circuit design – Ohm’s Law.  Build the circuit in lab.  Take it with you!

3. 3 SPIRIT Light Emitting Diodes (or LEDs)  A diode is a semiconductor electronic device.  A semiconductor is a material with a variable ability to conduct electrical current. Reference: http://electronics.howstuffworks.com/led1.htm

4. 4 SPIRIT Light Emitting Diode  A Diode is a common component in many electronic applications.  A Diode is a P-N junction that allows current to pass in only 1 direction, under the right conditions.  Light-emitting diodes, or LED’s emit light when current is flowing through the diode.

5. 5 SPIRIT Battery Tester  Use a LED to build a circuit that will indicate a good battery.  Connected Correctly, A Good Battery will Light up the LED! + DIODE -

6. 6 SPIRIT Designing the Circuit  OHM’s LAW will help guide how we design the battery tester circuit. Voltage = Current X Resistance V = I x R  Here,  V = Voltage has units Volts  I = Current has units Amps  R = Resistance has units Ohms

7. 7 SPIRIT Designing the Circuit  The conceptual design of the battery tester circuit (shown at right) will allow a very high (almost infinite) current to flow through the diode.  To prevent exceeding the current spec of the diode, we will use Ohm’s Law to limit the current. + DIODE - V = IR

8. 8 SPIRIT Designing the Circuit  Rearranging V=IR, we see I = V/R.  Choose a resistance R to achieve a current, I = V/R, that will be at a safe level for the diode, given the set value of V (e.g. 9 volt battery).  Solve the equation. V = IR

9. 9 SPIRIT Battery Tester Circuit + + - - Thus using Ohm’s Law, we arrive at the final Battery Tester Circuit design shown in this schematic:

10. 10 SPIRIT Building the Battery Tester Circuit  Soldering is a fundamental skill needed to assemble electronic projects.  The idea: Join electrical parts together to form an electrical connection.  Use a molten mixture of lead and tin (solder), together with a soldering iron. For more information, see: http://www.epemag.wimborne.co.uk/solderfaq.htm

11. 11 SPIRIT Soldering Electronic Circuits  Get components for battery tester circuit:  LED  Resistor  Battery Leads  Insert the component.  Splay the leads to hold the component in place. Photographs © 1996-2006 Alan Winstanley WORLD COPYRIGHT RESERVED

12. 12 SPIRIT Building the Battery Tester Circuit  Apply a clean soldering iron tip to the copper solder pad and the component lead, in order to heat both items at the same time.  Continue heating and apply a few mm. of solder.  Remove the iron and allow the solder joint to cool naturally. Photographs © 1996-2006 Alan Winstanley WORLD COPYRIGHT RESERVED

13. 13 SPIRIT Building the Battery Tester Circuit  The joint should be nice and shiny.  A bad joint: the solder failed to flow, and instead beaded to form globules around the wire. Photographs © 1996-2006 Alan Winstanley WORLD COPYRIGHT RESERVED

14. 14 SPIRIT Soldering Summary  All parts must be clean and free from dirt and grease.  Try to secure the work firmly.  "Tin" the iron tip with a small amount of solder. Do this immediately, with new tips being used for the first time.  Clean the tip of the hot soldering iron on a damp sponge.  Many people then add a tiny amount of fresh solder to the cleansed tip.  Heat all parts of the joint with the iron for under a second or so.  Continue heating, then apply sufficient solder only, to form an adequate joint.  Remove and return the iron safely to its stand.  It only takes two or three seconds at most, to solder the average p.c.b. joint.  Do not move parts until the solder has cooled.

15. 15 SPIRIT References  Information & Photo Source  How Stuff Works: http://electronics.howstuffworks.com/led1.htmhttp://electronics.howstuffworks.com/led1.htm  Copyright Notice Everyday Practical Electronics Soldering Guide: http://www.epemag.wimborne.co.uk/solderfaq.htm http://www.epemag.wimborne.co.uk/solderfaq.htm  Text © 1996-2006 Wimborne Publishing Limited, Wimborne, Dorset, England. Everyday Practical Electronics Magazine has provided this document as a free web resource to help constructors, trainees and students. You are welcome to download it, print it and distribute it for personal or educational use. It may not be used in any commercial publication, mirrored on any commercial site nor may it be appended to or amended, or used or distributed for any commercial reason, without the prior permission of the Publishers.  Photographs © 1996-2006 Alan Winstanley WORLD COPYRIGHT RESERVED  Presentation Created by: Alisa N. Gilmore, P.E. Department of Computer and Electronics Engineering, University of Nebraska- Lincoln, July 2006; updated July 2007; modified June 2009 by H. D.