Direct Drive 17mm linear regulator driver with 4 7135 chips and microprocessor If you apply the correct voltage, you don't need a driver at all. Lithium-ion batteries conveniently provide a decent voltage without any further modification. This is quite efficient since all of the power from the battery is delivered to the LED. However a fresh li-ion battery starts at 4.2 volts fully charged and will be 3.6 volts when it needs to be recharged. As power is applied to the LED, it will draw a certain amount of current from the battery. This current increases with the voltage. When the voltage is higher, the LED will be very bright and draw a great deal of current. As voltage decreases the light will dim and draw less current. If a constant brightness is desired, a driver that offers some kind of regulation is required. Also, many LEDs are being overdriven by 4.2 volts of a fresh li-ion battery.
next you'll be telling me, all flashlights without constant current regulators will kill the LED....
Next you'll be telling me, my flashlight no longer works because there's no current limiter in place, just a flashlight, LED and the body (ie, the heatsink) and i've used it > 500 hours.
The heatsink prevents it from getting hot enough to self destruct, something this LED string lacks... and i agree, current needs to be limited.
You probably don't agree with that either.... but there's PLENTY of people in the flashlight world who would tell you, you're talking crap when you say you need a constant current driver for ALL LED'S this is simply un freaking true.
And are you now going to claim that i never actually did this test and experimented with temperature ? even though i've had a 5mm LED running for days on end monitoring current and voltage? did it blow up after a week? no..
Did i place the LED in an unknown environment where it could get hot and self destruct? no...
Am i claiming it's safe to run it at it's max current to do this?.. no...
So it's not rubbish, it's fact... do i need to create an Arduino project to monitor the heat in the room and current draw over a range of temperatures and log the data ?
When adequately heatsinked, the temperature won't rise further increasing the current,
That is just rubbish, please try and refrain from making comments on things you do not know about.
I tried with a 10watt left it for days on end in 40c heat, monitoring it's current draw, I've done it, it works fine I have the proof, I'm using the same method as we speak for an ssc p7 driving it at a constant 3.8v which has been pulling a steady 280ma for days on end. .
That is not how you make a meaningful test of things. Perhaps living in 40C heat has affected more than you think. Any component dissipating power will get hotter that the heat sink. It has to, this is the law of thermodynamics. This will form a temperature gradient between the component and the heat sink. This happens no matter what the ambient temperature is.
So yes, providing it's heatsinked, driving an led by voltage is safe to do...
No it is not!!! You over simplify things. You can not make sweeping statements like this. Well of course you can make a statement like this but it is very wrong.
So please don't bring 20ma little leds into the argument.
If you had bothered to read this thread from the start you will have realised that it IS about small LEDs NOT power LEDs. You have got hold of the wrong end of the stick again!
This is about the FORWARD voltage of the LED and if it's safe to do so, yes it is.... if you can control the temperature and a heatsink would do it adequately
it's called "Direct Drive" higher powered LED's have a base in which to transfer the heat, Surface Mount also have this ability and this is surface mounted... if he ran this LED at say 60% of the max current allowing for heat fluctuations, it would be safe.
yes, these are surface mount LEDs but not soldered directly to copper pads which i thought they were, but my argument still stands.... run these 30% below the max forward voltage, to account for heat fluctuations, and it will be fine... but due to their size and lack of heatsink, it is a concern.. i'd probably not attempt it with this string.