I can't remember where I saw the recommendation, but I bought these LEDs on eBay. I have emailed the seller... no reply. Do these types of LEDs have polarity? Do I need add a resistor to one side vs. the other? (1K according to the decoder manual.)
The listing normally says if they have a resistor included and the red wire is positive.The listing normally has the voltage and current listed. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
The resistor can go in series with either wire and when you hook it up if the LED comes on its correct if not reverse the wires. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
Yes, it doesn't matter what side of the LED you place the resistor on. For consistency, I always put it on the common (-) side but - again, it doesn't matter.
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
Than you for the help. Used the multimeter to figure out positive out of the decoder, then wired in the resistor. Success!
I have found that even using a 1KΩ on the tiny SMD LEDs that they are too bright with the typical 12V source. I keep 1.6KΩ, 2KΩ and 2.2KΩ on hand. Try higher values, there's no need to run them super bright.
Resistor assortments are dirt-cheap at Amazon.
Good Luck, Ed
Positive on the dfecoder is the blue wire, or will be marked with something like F0+ or COM or F+ if it doesn't have wires.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
The only 'polarity' is in the LED (think the 'diode' in light-emitting diode). A resistor is inherently a nonpolar device (it doesn't care which way the current goes through it, it is an equal-opportunity dissipator).
You hook up the LED with the polarity that lights it; and the resistor where it fits most effectively (and won't melt anything if it heats). If you hook it up in reverse with the resistor in circuit 'anywhere', it just won't light -- it is dioding, of course. That does not mean you have let the magic smoke out, it means you reverse the wires.
If in doubt, start with high resistance and go lower. Even very high resistance will likely produce some forward current that produces light when the LED is connected in its forward polarity.
He said he has a multimeter, the lowest ohm range will put a glow in a LED to check for a working LED and polarity. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
gmpullman I have found that even using a 1KΩ on the tiny SMD LEDs that they are too bright with the typical 12V source. I keep 1.6KΩ, 2KΩ and 2.2KΩ on hand. Try higher values, there's no need to run them super bright. Resistor assortments are dirt-cheap at Amazon. Good Luck, Ed
I totally agree with, Ed. I actually used 10KΩ resistors for some 0603 SMT LEDs that I installed in a few brass locomotives recently and they were plenty bright.
tstage gmpullman I have found that even using a 1KΩ on the tiny SMD LEDs that they are too bright with the typical 12V source. I keep 1.6KΩ, 2KΩ and 2.2KΩ on hand. Try higher values, there's no need to run them super bright. Resistor assortments are dirt-cheap at Amazon. Good Luck, Ed I totally agree with, Ed. I actually used 10KΩ resistors for some 0603 SMT LEDs that I installed in a few brass locomotives recently and they were plenty bright. Tom
Rich
Alton Junction
Not all meters can light an LED - the cheapo HF ones I have do not, they run on a single coil cell. My two better handhelds run on sets of AAA and AA batteries - those will light an LED fine in the diode test mode - if the polarity is right.
On those pre-wired LEDs, the red is PROBABLY +, but never assume. A 0V battery and a 1K resistor make for quick testing.
I have about a dozen HF cheapos and I haven’t tried all of them but all the ones I’ve tried have got enough to light a LED. I did replace a battery in one of them a couple of years ago and as I remember it was a 9 volt battery. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
There are a few different models - mine don't have the transistor checker. Buying a new battery cost more than I paid for the meter
Thanks Randy!I was going to check a couple of my HF cheapo meters and the first three I picked up wouldn’t work. One had a dead 9 volt battery, the second one was just dead, a no go even with a new 9 volt battery. The third won’t work on resistance, works on voltage OK.The next 4 worked OK and all would light a warm white LED on the 200Ω scale.Two of them are headed to the county dump.I use a sharpie to mark the new date, the dead as a doornail was dated 2016 the no resistance was dated 2009.No big deal, I had two unopened meters in my closet.All of my HF cheapo meters were freebees with a purchase. EDIT:
I found a crack between the input jacks and the main board on the dead as a doornail meter, saved one from the dump.
Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.