LED with built in resistor

julianE

Senior Member
I hate to ask such a basic question but have had little luck finding LEDs with built in resistors. I used to buy them from phanderson's site, they came in a package of ten.
Red LEDs with built in 330 ohm resistor. I'm thinking someone must sell them on ebay but so far i can't find them.

Thanks in advance.
 

eggdweather

Senior Member
There's useful table in this link for R values for a given forward voltage (colour of LED) and supply voltage:http://www.ebay.co.uk/itm/50-x-LED-Resistor-for-5v-6v-9v-or-12v-Supply-leds-/291238617739?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item43cf2ca28b
You need to be searching for LED's designed for a given supply voltage e.g. 5v or 12v or whatever. Usually they are constant current drivers in them, example: http://www.ebay.co.uk/itm/Kingbright-5V-3mm-LED-Green-4-Pack-/291210585637?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item43cd80e625
 

erco

Senior Member
I hate to ask such a basic question but have had little luck finding LEDs with built in resistors. I used to buy them from phanderson's site, they came in a package of ten.
Red LEDs with built in 330 ohm resistor. I'm thinking someone must sell them on ebay but so far i can't find them.

Thanks in advance.
See Mouser.com they have Kingbright LEDs w integral resistors.
 

lbenson

Senior Member
Digikey 67-1103-ND, tho the last time I looked, the description didn't say they were "resistorized" (but they are).
 
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Jeremy Harris

Senior Member
The Kingbright ones are very useful. Here they are often described as "5V LEDs". I usually get them here in the UK from Rapid. Handy if board space is tight, as they can be driven directly with no need for a series resistor.
 

julianE

Senior Member
Thanks for all the replies. I checked my old receipts and they were $2.50 for a pack of ten from phanderson, i must have been flush back in the day cause now the price seems high.
Mouser is just a hair over $2 for 10. I will have to wait to build up the order in order to save on shipping. i found one possibility on ebay,

http://www.ebay.com/itm/PBB-New100-LEDs-Red-High-Output-5mm-6V-LIGHT-Super-Bulb-Lamp-Diode-SSY-2292-FQ33-/141546349645?pt=LH_DefaultDomain_0&hash=item20f4d1e44d

These LEDs are super convenient. Thanks for all the help.
 

julianE

Senior Member
I believe that the reference to 6V is the reverse voltage rating.
No mention of inbuilt series resistors.
Looks like I'm out $2.26. Not the clearest of descriptions "6V LIGHT Super Bulb Lamp", would have never guessed they meant reverse voltage. Oh well, live and learn.
 

WHITEKNUCKLES

New Member
What is the modern penalty for Heresy?

On a different forum on a thread for rc navigation lights I was delighted to see posts #3 and #5 on the simplicity of using Picaxe for this purpose.
"rcgolf" described his learning path with Picaxe extolling it's virtues and capabilities and recommending this forum.
He showed a minimalist Picaxe 08M circuit using only wires and 4 LEDs and a 'foamie' video of it working after months of use.
Since that time I have used LEDs direct to Picaxe without resistors for similar risk free projects including a couple that have run all night long for more than 4 years.

I remembered his 'name' and did a Google search.
rcgolf navigation lights

Dave
 

hippy

Technical Support
Staff member
Having found the other forum 'rcgolf' seems to be under the impression that the PICmicro current limits its individual pin outputs to ~20mA.

As I understand it that is not true. There is an interaction such that, as current draw increases the output pin voltage drops, but that is not the same as being current limited.
 

AllyCat

Senior Member
Hi,

No, there is no "current limit" as such. However, the minimum "guaranteed" output currents (in the Microchip base PIC data sheet) are remarkably low (less than 10 mA pull-up for example). So anyone who calculates that (for example) a PICaxe output pin on a 5 volt rail will always deliver 20 mA through a 220 ohm resistor into a transistor base is being very optimistic. ;)

But a current limiting resistor still should be used, because one might be "unlucky" and have a "good" device with a driver stage that can deliver more than 25 mA (the absolute maximum rating) from one of its pins, and thus potentially destroy itself.

Cheers, Alan.
 

julianE

Senior Member
I once mistook a regular LED for one with a built in resistor, the resistor free LED survived but it was rather hot to the touch, i'm fairly certain it would have given up the ghost if I let it shine for a few minutes more.
 

WHITEKNUCKLES

New Member
Greetings julianE.

Can you please tell me if the regular LED that you mention was driven by a Pickaxe output when it was rather hot to the touch?
This would imply a high output from the Picaxe, if so did it survive?

Dave
 

julianE

Senior Member
Yes, I had the LED directly to the picaxe output pin. Steady on, only one output was active. I noticed the LED getting less bright, realizing my error I yanked it out and noticed it was warm. It did survive, the picaxe was running at 5 volts, I suppose if run at 3.3 v it might have been OK. I'll be getting a 100 red LEDs soon cause I didn't read the eBay spec closely :)
 

nekomatic

Member
Has anyone ever found an SMT LED with a built-in resistor or current limiting circuit? That would be a nifty part for space-constrained circuits, especially if hand soldering.
 

srnet

Senior Member
Has anyone ever found an SMT LED with a built-in resistor or current limiting circuit? That would be a nifty part for space-constrained circuits, especially if hand soldering.
You do boards that are so small that there is not room for a 0603 (or smaller) SMT resistor ?
 

nekomatic

Member
No, I don't have a pick and place setup or a reflow oven so if I ever do need to use SMT parts instead of through-hole I want to have as few of them to deal with as possible :)
 

elanman99

Senior Member
What happened to LEDs with built in constant current circuits?

I still have a couple of these (5mm type) that I got from RS some years ago. They are better concept than just a resistor because that work at the same brightness and current over a wide voltage range. I used to use them as the current source (12.5mA) required by equipment but they doubled as the power 'ON' indicator.

I have one in a small testbox that contains nothing other than a battery. I use it with a meter to check the Zener voltage of diodes as its much easier than reading the markings!

Ian
 

eggdweather

Senior Member
I think suppliers/designers have forgotten what a simple and somewhat perfect solution they offer and easy to implement too!
 

srnet

Senior Member
I think suppliers/designers have forgotten what a simple and somewhat perfect solution they offer and easy to implement too!
Start from the assumption that designers and suppliers of semiconductors are actually as clever as the people in these forums, and they do understand what they are doing and there are reasons for why they do it.

So there must be a good reason for not producing combined LEDs\Resistors in SMT, so what could it be ?

Maybe the demand for such a device is so low that no one makes them ?
 

eggdweather

Senior Member
That is most likely to be exactly why they are not available as products and solutions are driven by economics, however there are few if any applications or devices that can drive an LED correctly, thereby requiring a series R to always be used/required!
 
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nekomatic

Member
I assume that with the increasing use of SMT and automated (or offshored) manufacturing, the cost penalty for adding an extra resistor in a commercial design is next to nothing and so there's not enough demand for such a product. Thought it was worth asking though.
 

geezer88

Senior Member
One problem I can see with the LED/resistor as a product is that the resistor would change depending on the voltage to be used.

Maybe a better all in one product would be a LED with built in current source so that the voltage could be anything in a fairly wide range. That solution would require a couple of resistors and a transistor. I do not know if they could be economically added to the LED die.

tom
 

elanman99

Senior Member
One problem I can see with the LED/resistor as a product is that the resistor would change depending on the voltage to be used.

Maybe a better all in one product would be a LED with built in current source so that the voltage could be anything in a fairly wide range. That solution would require a couple of resistors and a transistor. I do not know if they could be economically added to the LED die.

tom
Tom

That is exactly what we were discussing and what the link in message number 25 refers to.

Ian
 
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