My question is fairly simple. I am building an SMD LED board and i am limited in space. So originally i was planning on going with through hole resistors, but have it being i'm very limited on space i'm looking at the option of going the smd resistor route.

Essentially what i need is a 68 ohm 1/4 w through resistor but i want to use an smd resistor. When i type in 68 ohm 1/4 smd in ebay it showed me the 1206 SMD type (here's the link) http://www.ebay.com/itm/50-Value-1206-SMD-Resistor-Kit-0R-10MR-5-5000pcs-/330655035675?pt=LH_DefaultDomain_0&hash=item4cfc93711b *i then got excited and realized that a 68 ohm SMD might not be the same as a 68 ohm 1/4w through hole resistor, so what would be the equivalent to the through hole resistor in a smd resistor type

It has all the ones i require but i want to be sure i'm buying the correct ones. Again i apologize for the such noob question but i want to be sure i buy the correct one before i burn out my LED.

and on a side note. i use an LED calculator (link) http://led.linear1.org/led.wiz

Do you guys think it gives the correct values for and SMD LED as well. Any suggestions i will happily take. I like learning the correct way of all things i've been doing bad.

Thank you in advance

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    \$\begingroup\$ Why would you look for your components on ebay? \$\endgroup\$ – PlasmaHH May 26 '15 at 22:08
  • \$\begingroup\$ The cheapest ones i can find. I know i wasn't too happy with posting the word ebay on here.. \$\endgroup\$ – fgmoren312 May 26 '15 at 22:10
  • \$\begingroup\$ If you can spare the board space, a double-sided copper pour with vias directly under the resistor body can act as a heat sink providing more engineering for your circuit. \$\endgroup\$ – Ignacio Vazquez-Abrams May 26 '15 at 22:18
  • \$\begingroup\$ @fgmoren312: hard to tell without knowing how much you want and if you can use the other ones from that package (btw. I do not like having just a bag of loose smd components, at least a cut reel it should be), and this is really not the right site to discuss shopping things, but you should be able to find that resistor for 4-5c in low, and 0.2-0.5c in larger quantities. \$\endgroup\$ – PlasmaHH May 26 '15 at 22:21
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    \$\begingroup\$ Oh, hell yeah, don't buy loose baggies of SMD resistors, ever. The reel (or partial reel) is worth paying for. And you can get a 5k reel of Panasonic resistors for $23. \$\endgroup\$ – Ignacio Vazquez-Abrams May 26 '15 at 22:26

Resistance is resistance; there is no difference between using a 68ohm TH resistor, a 68ohm SMD resistor, or a 68ohm carbonized strand of cotton, assuming resistance is the only criterion you care about. It isn't, but you've already handled power dissipation by specifying a certain amount and finding an appropriate SMD resistor.


The eBay listing for the 1206 packages clearly lists them as being 1/4 watt:

This is an assorted kit of 5000 components as listed below. They are all bagged and labeled, are all 1206 size. The tolerance is 5% 1/4 W . 100 components of each value.

1/4 W SMT is the same as 1/4 W through-hole as for as power dissipation even though they are physically smaller.


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