Need help with LED votlage - Page 1
Forum section: electronics / projects

author: poisonedshroomz
author_rank: Contributor
timestamp: November 15, 2015, 11:27:03 pm
content: Hi, I am trying to figure out the voltage and or current of this 2w LED for a another project I am working on.Any help is appreciated. I have attached pictures and followed the traces to draw out a schematic... which is probably wrong lol.The last resistor I couldn't work out its value not sure of the coloursalso I'm kind of a Novice at this so try and dumb it down a little bit if you can lol.thanks.

author: Srbel
author_rank: Frequent Contributor
timestamp: November 16, 2015, 07:55:30 am
content: 220V?

author: hayatepilot
author_rank: Frequent Contributor
timestamp: November 16, 2015, 08:07:28 am
content: Can't you just measure the LED voltage?Greetings

author: mij59
author_rank: Frequent Contributor
timestamp: November 16, 2015, 08:30:17 am
content: Its probably a 1W led, the 2W refers to to total power of the unit.BTW in your schematic is a capacitor missing, its parallel on R1.

author: Psi
author_rank: Super Contributor
timestamp: November 16, 2015, 08:35:26 am
content: 3.2V 350mA LEDs are quite common.Add in driver efficiency and some wiggle room and that's probably about right.

author: Srbel
author_rank: Frequent Contributor
timestamp: November 16, 2015, 08:40:16 am
content: Quote from: mij59 on November 16, 2015, 08:30:17 amThan it's not an 220V LED array. Ignore this:Quote from: Srbel on November 16, 2015, 07:55:30 am

author: poisonedshroomz
author_rank: Contributor
timestamp: November 16, 2015, 08:59:17 am
content: I don't think I missed anything on the schematic... Someone mentioned to me it could be a 50v led? I have another one I have taken apart and tried to power the led with no success using AA batteries.Sent from my SM-G900F

author: IanB
author_rank: Super Contributor
timestamp: November 16, 2015, 09:17:06 am
content: Quote from: poisonedshroomz on November 16, 2015, 08:59:17 amAll white LED chips operate on about 3.2 V and use from 10 mA for small ones up to a few hundred mA for big ones. Note that the big ones must be attached to a heat sink or they will be quickly be damaged.Sometimes many LED chips are placed in series (and parallel) in a single package and this makes them require a higher operating voltage, but they are still multiples of 3.2 V internally.The LED in your picture looks like it has four dies, so it may be a 2x2 arrangement and then it would need 6.4 V to drive it. You could try it with a 9 V battery and a 47 ohm series resistor and see if it lights up. If it does light up, measure the voltage across it with a meter. This would give you an idea of its normal operating voltage.Since the package claims 2 W and all such labels are optimistic, consider it to be a 1 W LED. If you measure the operating voltage and divide that into 1 W it will give you a typical operating current.

author: onlooker
author_rank: Frequent Contributor
timestamp: November 16, 2015, 01:36:01 pm
content: QuoteThe board showed C1 and C2 while the drawing had only one C. The yellow block may be the other C that is parallel to R1, otherwise R1 will be too high.If R2 is indeed 1k, the LED can only be a high voltage string (maybe even more than 50V).What is the role of R3?2W rating for the LED can still be true, but, the die needs to be at near room temperature. Since maintaining such temperature is impossible for power LED in real use, the wattage is derated (go by datasheet). eBay seller/mfg may intentionally confuse the LED rating with the real usage rating.

author: djQUAN
author_rank: Frequent Contributor
timestamp: November 16, 2015, 02:10:04 pm
content: Looks like a Seoul Semiconductor LED[sample image]but with four chips in series rather than in parallel.The paralleled version is specced at 3.3V forward voltage so that LED would need about 13.2V. You'd need to figure out the current limit where it doesn't get too hot.

author: poisonedshroomz
author_rank: Contributor
timestamp: November 19, 2015, 09:52:01 pm
content: Yeah, I thought maybe r1 and r3 were dropping down the voltage instead of a transformer and r2 was acting as a current limiter? Cap just for smoothing.Sent from my SM-G900F

author: poisonedshroomz
author_rank: Contributor
timestamp: November 19, 2015, 09:54:26 pm
content: It's out of a Philips bulb incase that makes any difference. Closest one I could find to it on their site was a 3w rated bulb.Sent from my SM-G900F

author: poisonedshroomz
author_rank: Contributor
timestamp: November 19, 2015, 09:57:52 pm
content: Might just conquer my fears and attach it to a plug and measure the voltage. Will likely need a step up circuit to run it from a battery though any recommendations on a small efficient one? If there is such a thing lolSent from my SM-G900F

author: KL27x
author_rank: Super Contributor
timestamp: November 20, 2015, 04:20:03 am
content: QuoteI use a little 12V alkaline "car alarm remote" battery with a 2k series resistor on a bit of protoboard for measuring LED/diode voltage drop (and verifying color/brightness/anode). It plugs into a socket I put in one of my (low voltage-only) DMMs and/or into a tweezer probe for SMD work. Set to DC voltage test and plug in the battery. Much easier to use this way without needing four hands.As I wrote this, I had to look up. Yep, it's still there. Maybe one day someone will design a DMM to take one of these tiny batteries for a high voltage diode check for LEDs and zeners. It would last for 10 years!

author: poisonedshroomz
author_rank: Contributor
timestamp: November 20, 2015, 09:36:04 am
content: I have tried a 9v not got a 12v. Will need to pick one up.Sent from my SM-G900F

author: djQUAN
author_rank: Frequent Contributor
timestamp: November 20, 2015, 11:14:05 am
content: See my comment above^you may need more than 12V for it to light up. Wire two 9V batteries in series then add a current limiting resistor.

author: poisonedshroomz
author_rank: Contributor
timestamp: November 20, 2015, 11:18:43 am
content: Yeah its on my list of things to buy, along with some resistors though I maybe able to salvage them from old stuff.Sent from my SM-G900F

author: IanB
author_rank: Super Contributor
timestamp: November 20, 2015, 05:16:00 pm
content: Quote from: poisonedshroomz on November 20, 2015, 09:36:04 amTry two 9 V batteries in series...QuoteWhy do we need to know that?

author: poisonedshroomz
author_rank: Contributor
timestamp: November 20, 2015, 05:51:20 pm
content: QuoteWhy do we need to know that?Because i sent it using tapatalk and I haven't really set it up yet.... happy now?

author: poisonedshroomz
author_rank: Contributor
timestamp: November 20, 2015, 10:53:40 pm
content: Ok so I just connected it to the mains (the full one I have, not the dismantled one)and measure the voltage across the led. It's 207v?!?! I didn't know they made any like that. I'm not to sure how to get the amps setting to work on the dmm every amp setting I put it on, it just jumps to 1 on the left side of the screen. Anyone know?Put down the crack pipe son!

author: crispy_tofu
author_rank: Super Contributor
timestamp: November 21, 2015, 09:49:21 am
content: Quote from: poisonedshroomz on November 20, 2015, 10:53:40 pmHave you put the probes in the right jacks? Also, has the fuse blown?Quote from: poisonedshroomz on November 20, 2015, 10:53:40 pmUhhhhh

author: poisonedshroomz
author_rank: Contributor
timestamp: November 21, 2015, 09:56:07 am
content: Yeah, I put the probes on the positive and negative side on the led itself... just checked again and it hit 210v there is only a 1a fuse in the plug and the 1a fuse on the board looks ok.Put down the crack pipe son!

author: poisonedshroomz
author_rank: Contributor
timestamp: November 21, 2015, 09:59:44 am
content: Got a picturePut down the crack pipe son!

author: poisonedshroomz
author_rank: Contributor
timestamp: November 23, 2015, 05:58:47 pm
content: Anyone know how I can run this from a battery? 210v @ 9.5mah is it possible?"Put down the crack pipe son!"