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 LED Light testing How-to & Homemade testers
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Author Previous Topic: Have You Had a Quickie Lately? Topic Next Topic: Fine Scale Miniatures, the I.M.DUNN Co.  

desertdrover
Engineer



Posted - 03/19/2018 :  3:45:11 PM  Show Profile  Reply with Quote
There are many questions from Forum members on how do I test an LED. Here are four (4) How-to ways to accomplish this task. Depending on your needs or skills these are some pretty simple ways to get the job done. Starting 1: with a Digital Multimeter, 2: using 9 Volt battery with 1K Ohm resistor in-line homemade tester, 3: using two (2) double A batteries, or 4: a nifty little gadget from Ngineering using a Nine (9) volt battery with a circuit board with installed resistors for testing LEDs.
Starting with the use of a Digital Multimeter, connect the Black test lead to the COM jack and the Red test lead to the Note that the polarity of the Red test lead is +).
Set the meter Function switch to the range (see picture below) and connect the test leads across the diode/LED. If the LED does not light, switch your red and black leads on the LED. When the LED lights whatever black lead clip is on your LED leads will be your (-) Neg. Cathode lead and that is where your resistor will be placed when installing into your Locomotive, Rail Critter, Structures or any LED lighting situation.



Second method using a homemade 9 Volt battery with 1K Ohm resistor in-line homemade tester. Get a set of red and black wires on a 9 volt battery snap on clip, and place an LED holder, or red and black alligator clips, on the other end of the red and black wires. Place a 1K Ohm resistor in-line on the black wire. To test an LED, place the LED into the LED holder, or use your alligator clips, and again if it lights, note what lead the black wire goes to on the LED leads, and that is your (-) Neg. Cathode lead and where your resistor is attached.



Third method using a double A battery case with two (2) double A batteries homemade tester. Attach a set of red and black alligator clips to the battery case red and black wires. (No resistor needed for this tester) Connect your LED to the tester clips and again, if it lights, note what lead the black wire goes to on the LED leads, and that is your (-) Neg. Cathode lead and where your resistor is attached for when you install it into your locomotive decoders White (Forward) or Yellow (Reverse) light leads.



The last LED tester is a device made by Ngineering, Part #N8021, for testing LEDs, nothing more than the same as your homemade second tester using a nine (9) volt battery and resistor. This device already has a resistor installed into a circuit board with nice convenient attachment clips for your LED leads. And same as all the other testers, the black lead shows your (-) Neg. Cathode lead and where your resistor gets attached prior to installation.



Also posed into the DCC, Computers and Electronics for Model Railroads
http://www.railroad-line.com/forum/topic.asp?TOPIC_ID=50357

Country: USA | Posts: 17278

mecrr
Engine Wiper



Posted - 03/20/2018 :  1:56:52 PM  Show Profile  Reply with Quote
I use the Ngineering tester that I purchased from Microlumina a few years back, works like a charm and yes cost more, but no need to assemble, and no wires that get in the way.Its compact size makes for a might nice little unit.
David



A Maine Expatriate living in the valley of Northern California - Modeling in HO.
David Stickney

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jbvb
Fireman

Premium Member


Posted - 03/20/2018 :  11:04:03 PM  Show Profile  Visit jbvb's Homepage  Reply with Quote
Very complete coverage of the subject, Louis.


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desertdrover
Engineer



Posted - 03/21/2018 :  08:42:34 AM  Show Profile  Reply with Quote
quote:
Originally posted by mecrr

I use the Ngineering tester that I purchased from Microlumina a few years back, works like a charm and yes cost more, but no need to assemble, and no wires that get in the way.Its compact size makes for a might nice little unit.
David




quote:
Originally posted by jbvb

Very complete coverage of the subject, Louis.



David, that Ngineering tester is a great little gem. As you can see I've bought one for myself as well. However, I started out many years back using just the 2 double "A" battery tester.

James, thanks for your comment! I still would like to see your PDF on the subject though if you are willing to pass it along to me. I'm always interested in these types of clinics.



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MarcusF
Section Hand

Posted - 03/21/2018 :  08:58:20 AM  Show Profile  Reply with Quote
A very good summary!

NCE has a rather nice LED tester that allows you to try the LED with varying levels of current, plus some extra feature that I can't recall, and can't find the manual (in neither my workshop nor the craptacular NCE website). Unfortunately it's only available with their LED lighting kit, which at $60, is a bit spendy for what it is.
I have a rechargeable 4.8v NiMH battery and some small 3.7v lipo batteries from RC trucks and planes that I use. They have a small connector that the pins from the LED slide easily into.



Edited by - MarcusF on 03/21/2018 08:59:11 AM

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desertdrover
Engineer



Posted - 03/21/2018 :  3:02:03 PM  Show Profile  Reply with Quote
quote:
Originally posted by MarcusF

A very good summary!

NCE has a rather nice LED tester that allows you to try the LED with varying levels of current, plus some extra feature that I can't recall, and can't find the manual (in neither my workshop nor the craptacular NCE website). Unfortunately it's only available with their LED lighting kit, which at $60, is a bit spendy for what it is.
I have a rechargeable 4.8v NiMH battery and some small 3.7v lipo batteries from RC trucks and planes that I use. They have a small connector that the pins from the LED slide easily into.



These NCE testers are great also, but their price is crazy, when all you want is the tester. These testers can be bought for $3.00 other places, and on eBay, made by the same people that make it for NCE. (See picture of NCE tester and generic tester picture shown). This handy device is for testing LED's by plugging in your LED into the correct holes (all of which are marked) and just push the button to see its brightness, illuminant color, etc., for testing LED's (2-150mA)
The top row is for 2 pin LED's with currents ranging from 2mA-30mA
The bottom row is for 4 pin LED's (piranha LED's) with currents ranging from 20mA-150mA





Edited by - desertdrover on 03/21/2018 6:46:24 PM

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Carl B
Fireman

Premium Member

Posted - 03/21/2018 :  7:49:51 PM  Show Profile  Visit Carl B's Homepage  Reply with Quote
Well done Louis.

I own the N8021 LED tester and use it regularly. I can't live without it!



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