Thanks, Dave. As someone who is electronically challenged, I'm really going to appreciate this series.

I am also electronically challenged, so I am looking forward to this series. Thanks for taking the time to put it all together.

A very helpful video. I am looking forward to the next ones. Two things I have heard : 1- Using lower voltage than the LED's maximum will make the light dimmer (as you showed in the video); but it also prolongs their life. 2- If you wire resisters in series, their resistance is added. To get the 800 ohms you wanted, simply use two 400 ohm resisters in series.

Fantastic video Dave..looking forward to the next Elec Trainics basic video.. you made LED Basic easy to understand..

Great video Dave. Thanks for sharing

My first foray into LED lighting was a disaster. Knowing nothing I blew bulb after bulb until it dawned on me I needed to add the resistor. This is a good explanation of that Dave. You will save a lot of frustration with this video. Well done!

That was a great insight into leds Dave, interesting, I learned stuff, that's always good, lol.

Excellent Dave, you done the good job. JerseyBill

Cool walkthrough and review of the various set-ups!

Very nicely done Dave. I'm might learn something ;-)

Good video. One correction, though...the resistor isn't voltage limiting, it's current limiting. If you put your voltmeter on that circuit when you turn it up, you'll see that your voltage is still what you'd expect it to be on the track. Otherwise, any time there's an LED put on the track circuit, it would impact the voltage also going to the train, since it's in parallel with the train.

Great how to do it video Dave

Great series, not knowing this , this will help greatly. Thank you

Great video as usual!

great video, great series idea! This would have been very helpful when I first started lighting my layout. ALOT of trial and error and blown bulbs. Keep up the good work, Dave...

Very educational Dave. Thanks.

Exciting times!

Great video Scott I just bought some of the strip led s for buildings wasnt sure where to cut - thanks for the info look forward to the next one in the seies

Hi Dave, was going to use cheap Christmas lights to light my houses lol , yep hoping to learn more

I think what that little tester will allow you to do is to see how many milliamps are required to give you the brightness you need for your project. As you should already know the voltage you will be using, once you know the current (mA) it's a simple matter of using Ohm's law to calculate the value of resistor to use.

Great intro, Dave. Funny enough, I don't remember my electronics instructor telling me about resistors 'sucking up' the extra voltage but, you made it clear what you meant! You might want tp read uo on Ohms Law (the basis of all electronics). Cheers, Jim L

Great video Dave

The higher the milliamp, the higher the amount of current LEDs can draw. Not all LEDS run at the same voltage and current hence the different range. Running the LED's at a higher current will shorten its life. Flashing LED's have a tiny chip inside them that make the diode flash. If your eyes are good, you can just see the black chip in them. The average LED runs at 2V@20mA LED stands for Light emitting Diode and come in the same family of components as bridge/rectifier Diodes.

I can tell you the secret magic formula to determine a dropping resistor. It is based on Ohm's law: E (Voltage) = I (current - amps) x R (resistance - ohms). The formula is: R = (Vss - Vled) / mA. Vss is the supply voltage minus Vled (LED voltage) (Note: this determines the voltage for the resistor) divided by the milliamp current of the LED. Since current remains the same in a series circuit, the milliamp current will be the same as the resistor current. So, the formula is an equivalent series circuit in Ohm's Law. As far as choosing a resistor, some values may not match the standard resistor values. A person will choose a value closest to the calculated value to the standard value or resistors can be added in series to increase the resistance or in parallel to lower the resistance to closely match the desired value.

Very informative ... nicely explained

A few points: On LEDs there usually is a rate maximum current which you never want to go above. There is also a thing called "test current" which is the one they use to check the brightness. In a lot of cases, you want to run the LED with under 1/2 the test current to make it not too bright for the application. Current ratings are usually stated in mA (milliamps) which is 1/1000th of an Amp. 20mA would be 0.020Amps. Ohm's law is not all that tricky once someone tells you that I is the Amps for reasons. (I will use * for times) V = I*R or I = V/R or R = V/I That last one is the one you will want in most cases. The LED is about 2V of drop. The supply voltage is 12V so there are about 10V to be gotten rid of. We want to run the LED at 10mA (for example) 10mA = 0.01A R = 10V/0.010A = 1000 Ohms For this reason, I* suggest you want some 1000 Ohm resistors. Each LED gets a 1000 ohm in line with it so each one gets the right current. Also: They make "amber" LEDs these look nicely like a flame based light or an old incandescent bulb. Because the needed current is so low, you can have a "wall wart" style power supply as a supply to run the LEDs. This way you can have them on with the power to rails turned off. You can get LEDs in a lot of interesting colors. It is worth looking at the colors and thinking how they will fit in with what you are doing.

When I test my micro LEDs or SMD LEDs I solder cut LED leads to the wires and use the tester. It takes time. I save the leads cut from used LEDs.

Another good one Dave. Those strip lights LEDs and resistor are what we call SMT (surface mount technology). Not sure if you're using an actual bridge rectifier (as we haven't seen the next episode yet) but you can build one from four 1N4001 rectifiers. There is a 700mv (.7 volt) drop across any silicone rectifier. In standard resistors (144 between 1ohm and 1 meg ohm) you have three between 680 ohm and 1K including an 820 ohm. In this case a 1K resistor works fine. Cheers

Ma refers to the current rating higher the ma more current flowing

I popped an LED the other day. I was testing to see which was positive and negative on the rear LED on a new KCS SD70ACe because I’m putting in a sound decoder. I had 3 resistors sitting there to check the light, and what did I do? I hooked it up strait to my tester, without the resistor and blew the damn thing. Dug out the light and board it was on and now I'm retrofitting another micro LED in it's place, with a resistor.

LED’s are current controlled devices, the higher the current the brighter the light. Given a particular voltage choose a resister so that you get the current you want, typically 10-20mA, using Ohms law V=IR. So for 18V supply, for 20mA you need 18/0.02 = 900 Ohms

Any suggestions on where would one get a 68-ohmn resistor? I need to replace one for a model train transformer.

Fortunately you chose a value of resistor that would limit the current flowing through the LED in order it did not blow. Unfortunately your theory was totally wrong. The 5mm LED would have a forward voltage of around 2-2.5 volts and a current flowing through it would be 20mA. If you were connecting to a 12 volt supply then you need to have a voltage drop of 9.5-10 volts across the resistor. To work out the resistance you would use the equation R=V/I (Ohms Law) which in this case R = 10/0.02 therefore R=500. Typically this would be a 470ohm resistor but you could use the next typical value up which would be a 680 ohm. Resistors come in 'Typical values' not all values are available.

Its not a bulb it's an LED. Bulbs get planted in the garden.