Recent purchase from Farnell - Page 1
Forum section: electronics / general

author: uwezi
author_rank: Unknown
timestamp: May 09, 2014, 08:24:36 pm
content: I just quickly wanted to share this week's experience with a purchase from Farnell (Newark).I had ordered 6 each of 1W LED chips in red, green and blue from Multicomp. Yes, I know, normally I would have done this for a significantly lower cost from a more or less trustworthy source on eBay - but this timeI could not wait 2-4 weeks for the deliveryout administrative system does not encourage this way and I did not want to pay (again) from my own pockethttp://www.newark.com/multicomp/703-0144/led-red-high-power-round-1w/dp/94T8882?categoryId=800000005522I made a circuit board, got the chips, soldered them onto the board and tested ...... and to my surprise/disappointment/frustration the "red" chips emitted, yes,yellowlight.Ok, to be fair, the actual semiconductor chip inside the LED is actually redish, but when I buy a red LED I normally expect an LED which emits red light - wouldn't you also?Even more strangely: Farnell does not even sell yellow LEDs from this series...If this had been a wrong delivery from a nameless Chinese seller on eBay, I probably would not even complain, but instead just place a new order, but in the case of an established distributor I think that this should not happen! No, it not even may happen!

author: ConKbot
author_rank: Super Contributor
timestamp: May 09, 2014, 08:32:21 pm
content: Strange, as the image shows a phosphor coated die, like what would be used in a white LED, but the data sheet not only says red, but lists wavelengths, which are red. But the chart for figure 1 is titled "WHITE LED Spectrum VS. WAVELENGTH" but shows a single peak that a red LED would have... what a mess.

author: mariush
author_rank: Super Contributor
timestamp: May 09, 2014, 08:56:29 pm
content: If you read the datasheet, you would notice at the absolute maximum ratings that they say : 5v @ 350mA , maximum 1067mWat 25c.Try lowering the current a bit, you may be pushing them too hard.And yes, ignore the pictures on Farnell or always double check them, they have a tendency to use the same picture for a category/series of products. Always check with the datasheet.

author: guido
author_rank: Regular Contributor
timestamp: May 09, 2014, 10:17:42 pm
content: I once purchased some parts, including a small choke. Got the parts but one; also got a bag with a DB9 to DB25 cable, nicely labled CHOKE RF CONFORMAL COATED 47UHIt is still in the bag.

author: uwezi
author_rank: Unknown
timestamp: May 10, 2014, 10:31:18 am
content: Quote from: mariush on May 09, 2014, 08:56:29 pmBe assured that I did not push them too hard. I tried them with a multimeter on the "diode" setting, as well at different currents between 10 mA and 200 mA. The LEDs emit a single wavelength at around 580-590 nm (haven't measured it yet).I first thought I might have done soemthing to the LEDs during the soldering and tested virgin LEDs out of the bag.As a comparison I then showed my students what happens if you put too much current through a green GaP LED: the emitted color turns from green over yellow to red.

author: amyk
author_rank: Super Contributor
timestamp: May 10, 2014, 12:29:25 pm
content: Quote from: guido on May 09, 2014, 10:17:42 pmWould like to see a picture of that."No, the choke is there - it's embedded inside the cable!"

author: AndyC_772
author_rank: Super Contributor
timestamp: May 11, 2014, 06:10:37 pm
content: I've had the opposite, "yellow" LEDs that actually glow a slightly orange shade of red.