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

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

3. 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

4. Common Symbols

5. Common Symbols

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

7. Fundamental Components
Resistor
Capacitor
Diode
LED

8. Key Formulas Voltage = Current x Resistance E = I x R
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

9. Key Formulas

10. 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

11. Resistor Color Code

12. Resistor Common Use ___ Ohms, ___ Watts What value goes here?
14Volt Power Supply
1.5 Volt
15 mA Lamp

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

14. Resistor Common Use Series Circuit
We will use OHM’S LAW and KIRCHOFF’s LAW
to calculate the value of the resistor
835
___ Ohms, ___ Watts
1/4
12.5 V
Ohms
12.5 V
0.015A X
0.1875W
0.015A
12.5 Volts
Voltage Drop
14Volt Power Supply
14 Volts
1.5 Volt
15 mA Lamp
1.5 Volts
14 Volts minus 1.5 Volts equals 12.5 Volts
Series Circuit

15. 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

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

17. What is a DIODE anyway?

18. What is a DIODE anyway?

19. Constant Lighting

20. The Ubiquitous LED 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

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

22. 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)

23. Basic Circuits Series/Parallel Circuit Parallel Circuit IC IC IC I T
= 210mA
This LED is on when
Vs is reversed IC 1 IC 2 IC 3
= 200mA
= 10mA
The Voltage Source is the same across each branch
Each branch has its own Current Flow
The sum of Ic1 and Ic2 or Ic1 and IC3= total current of the circuit

24. Handy – Dandy Tester - + + -

25. 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.

26. 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)

27. Examples

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

29. Power Routing Frogs

30. How It Works

31. How It Works

32. How It Works

33. 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 microFarads (μF)

34. 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 s, CC BY-SA 2.0

35. The Capacitor

36. Basic Capacitor Use Courtesy of Electronics Area
Courtesy of Electronics StackExchange
Courtesy of Electronics Area

37. Open Circuit vs Short Circuit

38. Open Circuit vs Short Circuit

39. Open Circuit vs Short Circuit

40. Recommended Tools Wire Cutters Wire Strippers Needle Nose Pliers
Variable Temp Soldering Iron
Electronic Solder (Kester "44" rosin core, SN63PB37, .015" diameter, part number )
Desoldering Pump (aka “Solder Sucker”)
Two Multimeters
Jumper Lead Kit
Experimenters Breadboard

41. 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

42. How to Measure Motor Current

43. Troubleshooting Dead Track
Good
Good
Rail Joiners
Good
Faulty track section
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.
BAD

44. Electronic Starter Kit

45. 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.
A voltage or current applied to one pair of the transistor's terminals controls the current through another pair of terminals.
Due to its design, the output power can be much higher than the input power, allowing it to act as an amplifier. N P

46. Fundamental Transistor Use
Used as a SWITCH
Used as an AMPLIFIER

47. 3 Light Signal Circuit

48. 3 Light Signal Circuit

49. 3 Light Signal Circuit

50. 3 Light Signal Circuit

51. Recommended Reading

52. THANK YOU for attending !
Questions?
THANK YOU for attending !