Basic Electronics for Model Railroaders Carl Marchand Suncoast

Basic Electronics for Model Railroaders Carl Marchand Suncoast Model Railroad Club Largo, FL

Dedication To Peter J. Thorne, for the guidance and inspiration that led to a career in Electronics and Computer Technology

What We Will Cover VERY BASIC Electronics – easy-peasy; not scary stuff How to troubleshoot electrical / electronic issues. Your Survival Kit – Tools and resources EVERY model railroader should have BONUS – 3 Light Signal Circuit

Common Symbols

More Symbols K = Kilo or x 1000, i. e. 1000 Ohms = 1 K Ohms M = Mega or x 1, 000, i. e, 2, 000 Ohms = 2 M Ohms ꭥ = Symbol for Ohms, i. e. , 500 Ohms = 500 ꭥ μ = micro = 1/1, 000 as in 100 microfarads = 100 μF

Fundamental Components Resistor Capacitor Diode LED

Key Formulas There are two basic electronic formulas to know/commit to memory (or at least write down!) Voltage = Current x Resistance E = I x R Power = Voltage x Current P= E x I

Key Formulas

What is a RESISTOR? In Model Railroad Electronics resistors are used: to reduce current flow (i. e. , lamps and LEDs) adjust signal and/or voltage levels bias active elements (control the turn-on of transistors, integrated circuits, detectors, etc. ) Come in a variety of resistance values, rated in Ohms and power capacities, rated in Watts Schematic Symbol for Resistor

Resistor Color Code

Resistor Common Use ___ Ohms, ___ Watts 14 Volt Power Supply What value goes here? 1. 5 Volt 15 m. A Lamp

Resistor Common Use ___ Ohms, ___ Watts What value goes here? 14 Volt Kirchhoff's voltage law (2 nd Law) states that the sum of all voltages 1. 5 Volt Power around any closed loop in a circuit must equal zero 15 m. A Lamp Supply Series Circuit

Resistor Common Use We will use OHM’S LAW and KIRCHOFF’s LAW to calculate the value of the resistor 12. 5 V 0. 015 A 833. 333 Ohms 14 Volt Power Supply 1/4 835 ___ Ohms, ___ Watts 12. 5 V X 0. 015 A 0. 1875 W 12. 5 Volts Voltage Drop 14 Volts Series Circuit 1. 5 Volts 14 Volts minus 1. 5 Volts equals 12. 5 Volts 1. 5 Volt 15 m. A Lamp

What is a DIODE anyway? A diode is the baseline fundamental semiconductor Current flows in one direction only Typical diodes have a Voltage Drop of 0. 7 Volts Primary Component in: Power Supplies Detection Circuits Constant Lighting

What is a DIODE anyway? PARTS OF A DIODE ANODE CATHODE A K DIRECTION OF CURRENT FLOW Current flows AGAINST the arrow

What is a DIODE anyway?

Constant Lighting http: //www. circuitous. ca/x. Const. Light. html

The Ubiquitous LED = Light Emitting Diode Symbol similar to standard diode Advantages: Draws very low current Little or no heat dissipation Comes in a myriad of sizes Useful in scales from Z-Scale up! Extremely long lasting Key advancement in Model RR lighting

The Ubiquitous LED SMD – Surface Mount LEDs 3 mm LEDs 5 mm LEDs

Basic Circuits Series Circuit Current flowing through each component is the same as the total (IT) The sum of all the voltage drops equals the Source Voltage (Vs)

Basic Circuits Series/Parallel Circuit I T = 210 m. A This LED is on when Vs is reversed IC 1 = 200 m. A IC 2 = 10 m. A IC 3 = 10 m. A The Voltage Source is the same across each branch Each branch has its own Current Flow The sum of Ic 1 and Ic 2 or Ic 1 and IC 3= total current of the circuit

Handy – Dandy Tester +- -+

Circuitron Tortoise™ • • The most popular switch machine in Model Railroading Two SPDT switches are built-in Motor’s DC resistance is 600 Ohms – low current draw. Can be controlled in various ways including DC panel switches or DCC stationary decoders.

Circuitron Tortoise™ The SPDT switches can be used for: • Signal System Control • Switch Position Status. • Powered Frog Routing – (one of the highest uses of the SPDT)

Examples

Examples Why / how does this wiring of LEDs and the Tortoise ™ work?

Power Routing Frogs

How It Works

The Capacitor A capacitor is two plates separated by a dielectric (old school definition). Stores energy in a static electric field (similar to a very short term battery) Electrolytic and non-electrolytic types Polarized and non-polarized types Draws current while charging. Supplies current when discharging. Smooths out power in DC power supplies (reduces AC ripple by “filtering out” the variation in current. Unit of Measure = Farad or micro. Farads (μF)

The Capacitor Allows AC current to pass through it Prevents DC current from passing through it Se By Eric Schrader from San Francisco, CA, United States - 12739 s, CC BY-SA 2. 0

The Capacitor

Basic Capacitor Use Courtesy of Electronics Stack. Exchange https: //electronics. stackexchange. com/questions/175098/where-exactly-doesthe-ground-line-go-in-an-ac-dc-power-supply Courtesy of Electronics Area https: //electronicsarea. com/basic-power-supply-block-diagram/

Open Circuit vs Short Circuit

Recommended Tools Wire Cutters Wire Strippers Needle Nose Pliers Variable Temp Soldering Iron Electronic Solder (Kester "44" rosin core, SN 63 PB 37, . 015" diameter, part number 24 -6337 -0007 ) Desoldering Pump (aka “Solder Sucker”) Two Multimeters Jumper Lead Kit Experimenters Breadboard

Why TWO Meters? In some cases, you may need to measure Current (I) and Voltage (E) simultaneously Meter Requirements: • Measure DC Voltage /Current • Measure AC Voltage / Current • Measure Resistance

How to Measure Motor Current

Troubleshooting Dead Track Good Rail Joiners Good Faulty track section BAD RECOMMENDED : to find the faulty connection(s) keep the locomotive in the bad section and with power applied to the working track sections, measure the VOLTAGE across the rail joiners. The bad connection will show a voltage, the good ones will not.

Electronic Starter Kit

What is a Transistor? A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power. Made of semiconductor material usually with at least three terminals for connection to an external circuit. N A voltage or current applied to one pair of the transistor's terminals controls the current through another pair of terminals. P Due to its design, the output power can be much higher than the input power, allowing it to act as an N amplifier.

Fundamental Transistor Used as a SWITCH Used as an AMPLIFIER

3 Light Signal Circuit