Author Topic: Identifying SMLED leads  (Read 609 times)

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Kentuckian

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Identifying SMLED leads
« on: December 12, 2018, 04:56:07 PM »
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Which is the cathode and which is the anode? Or, more directly, which lead do I solder the 1K resistor too? I have tried the Google but I must be asking the wrong way.

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MK

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Re: Identifying SMLED leads
« Reply #1 on: December 12, 2018, 05:04:02 PM »
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You can solder the resistor to either lead.  Most people do it on the cathode side but either lead is fine from the circuit's perspective.

RBrodzinsky

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Re: Identifying SMLED leads
« Reply #2 on: December 12, 2018, 05:45:14 PM »
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As MK says, you can put the resistor on either side. Typically, the arrow points to the cathode, but that isn’t always the case, either (particularly on Red LEDs, and I have never understood why). I always double check myself with my LED tester whenever I start an LED wire soldering session.
Rick Brodzinsky
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Billg

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Re: Identifying SMLED leads
« Reply #3 on: December 12, 2018, 05:45:47 PM »
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I never worry about anodes and cathodes when making up SMD's especially 0402's and 0603's.  I use an LED tester and just remember which color wire went in what hole to light the things.....As MK stated, you can place the resistor on either lead.
Bill W.

wvgca

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Re: Identifying SMLED leads
« Reply #4 on: December 12, 2018, 05:46:13 PM »
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you can solder a resistor to either end, but the led is marked, an arrow, or a smaller bump points to the negative end

Kentuckian

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Re: Identifying SMLED leads
« Reply #5 on: December 12, 2018, 06:09:08 PM »
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Thanks, everyone! I didn’t know led testers existed.
« Last Edit: December 12, 2018, 06:12:24 PM by Kentuckian »
Modeling the C&O in Kentucky.

“Nature does not know extinction; all it knows is transformation. ... Everything science has taught me-and continues to teach me-strengthens my belief in the continuity of our spiritual existence after death. Nothing disappears without a trace.” Wernher von Braun

Steveruger45

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Re: Identifying SMLED leads
« Reply #6 on: December 12, 2018, 06:41:48 PM »
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Yep, The point of the green arrow mark is pointing to the cathode (-ve) side.
Old saying I recall was “ I’m always negative with an arrow pointing at me”.
« Last Edit: December 12, 2018, 06:47:00 PM by Steveruger45 »
Steve
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Re: Identifying SMLED leads
« Reply #7 on: December 12, 2018, 07:24:49 PM »
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The LED and resistors are connected in series, so as others said, the location of the resistor is irrelevant.

You can build your own LED tester. See https://www.therailwire.net/forum/index.php?topic=46039.0
--- Peteski de Snarkski

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Steveruger45

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Re: Identifying SMLED leads
« Reply #8 on: December 12, 2018, 08:08:20 PM »
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Hey Pete, I see you made the tester 40 years ago.  Have you had to change the battery yet? 😀

Also, and I think I mentioned it before is that if you have one of those free with coupon and other purchase digital multimeters from Harbor Freight, like this one, you can test an led with that set on the 0-200 ohms scale.

Also, another plus is, as these cheapo meters tend to breakdown before the battery runs out they are a free supply of batteries to build your led tester😀
« Last Edit: December 12, 2018, 08:56:03 PM by Steveruger45 »
Steve
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eja

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Re: Identifying SMLED leads
« Reply #9 on: December 13, 2018, 12:40:48 AM »
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The LED and resistors are connected in series, so as others said, the location of the resistor is irrelevant.

You can build your own LED tester. See https://www.therailwire.net/forum/index.php?topic=46039.0


Sir, your posts like this are why you are such a valuable asset to this community.

Thanks !

ed

peteski

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Re: Identifying SMLED leads
« Reply #10 on: December 13, 2018, 02:08:47 AM »
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Sir, your posts like this are why you are such a valuable asset to this community.
Thanks !
ed

Thank you Ed!
--- Peteski de Snarkski

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MK

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Re: Identifying SMLED leads
« Reply #11 on: December 13, 2018, 08:28:10 AM »
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Peteski does make things lively on this board!  :)