High power leds and led strips

outro: is it possible, some easy way, to limit the current other than changing the resistor?

Simple answer, no.

But you could go for the "remove R330" option to make it a 500mA module.

outro: Also, I am not quite sure how to use this? It has only GND + Vcc?

It certainly has not! It has two wires labeled "Led out" which go to the led. And at the other end it has two pad's for the supply voltage. It has a bridge rectifier on it so polarity doesn't matter.

outro: How can I control it with an Arduino?

Told you that already ;)

septillion: I think all these three are based on the PT4115 chip which is a very popular chip. Although most modules don't break the pin out (aka, don't add a solder pad) the chip does support dimming via PWM. Just solder a wire directly to the chip and it's a very easy driver.

It's pin 8 of the chip aka the one next to the word "OUT". You can connect this pin to an Arduino pin. And of course the led GND and the Arduino GND need to be connected.

outro:
I googled a more accurate picture:

And does the “crazy” heat come from the PWM?

The “crazy heat” comes from ignorant fools (like whoever made that schematic) persisting in using THE WRONG KIND OF MOSFET for their design. For an IRF540, the RDS(on) is only provided for 10V VGS, which gives you a hint of what kind of gate voltage this was designed for. They don’t even provide graphs for gate voltages less than 4.5V.

A quick test in the datasheet is not the Gate Threshold Voltage (VGS), but the Static Drain-Source On-Resistance (RDS(on)) spec. You can get a rough idea of what kind of gate voltages a MOSFET was designed to be used for by what gate voltages this spec is provided for.

For example, even though the FQP30N06L (attached) does not state anywhere in the description that it is a logic level MOSFET, it provides an RDS(on) for both 10V and 5V. So this would be a suitable MOSFET to consider for a 5V system, but 3.3V would be pushing it.

On a more extreme end, the DMG6968 (attached) provides RDS(on) specs for 4.5V, 2.5V, and even 1.8V gate voltages. This would be an excellent FET to use for moderate currents in a low voltage system.

DMG6968 - N-Channel MOSFET.pdf (184 KB)

FQP30N06L - N-Channel Logic-Level MOSFET.pdf (677 KB)

@Jiggy-Ninja, thank you for your explanation, I didn’t know about this DMG6968, have to take a better look at it !
@septillion
I think I will solve my problem(s) with buying the following item(s):
http://www.ebay.com/itm/272502198541?var=571562633572

http://www.ebay.com/itm/401089836411?var=670618877036

I wanted to consult from you though, what do you think? Do the prices seem high & should I just roll with the 500ma? I did a small test, 700ma vs 500ma , the change is not that big, or I don’t notice it.

Attached pictures
(pic: 887 in 500ma)

IMG_3357.JPG

If you take a careful look at that driver board, you will see that it has a PWM input near VIN+. You don't need to switch power with a MOSFET.

Perception of brightness is highly nonlinear. Changes in intensity are much more noticeable when at brightness than high. It's the same as our perception of loudness.

I would indeed say 12 pound is on the high side for 10.

And if you use a module with a PWM capable chip you don’t need a external mosfet :slight_smile:

And yeah, I would go for 500mA now. Like Jiggy-Ninja said, our eyes are not linear and even a LED is not linear all the way. So yeah, the gain isn’t that big. And two extra pro’s for the 500mA: your leds will life longer and will require significant less heatsink :slight_smile:

Thanks for the answers, decided to skip buying those (for now at least!)
My last dumb question is, after desoldering the resistor, do I have to connect the removed part?

What do you mean by "connect the removed part"? Do you mean, bridge the solder pads? Then NO, then you'll blow the led. Like I said, it has two parallel resistors, just remove the one and done!

septillion: What do you mean by "connect the removed part"? Do you mean, bridge the solder pads? Then NO, then you'll blow the led. Like I said, it has two parallel resistors, just remove the one and done!

Exactly what I meant , thanks for correcting me !

Jiggy-Ninja: If you take a careful look at that driver board, you will see that it has a PWM input near VIN+. You don't need to switch power with a MOSFET.

Perception of brightness is highly nonlinear. Changes in intensity are much more noticeable when at brightness than high. It's the same as our perception of loudness.

I started working on the board now, and I can't find the PWM input near VIN+ ? Are you referring to my 900mA driver?

I think for the PWM I need to solder pin 8 of the IC near the outs?

outro: I started working on the board now, and I can't find the PWM input near VIN+ ? Are you referring to my 900mA driver?

He wasn't ;) The other module you showed had the pin broken out. The one you have don't.

outro: I think for the PWM I need to solder pin 8 of the IC near the outs?

Exactly! See reply #20 ;)

septillion:
He wasn’t :wink: The other module you showed had the pin broken out. The one you have don’t.
Exactly! See reply #20 :wink:

Alright, I’m almost there!
This is very amazing.

I had some trouble getting the R300 off, (see images) but I managed.
I hope I didn’t manage the board (quite a lot of heat…)

See pictures for reference :slight_smile:

  • I was able to get it off easily by adding a lot more solder and then using the ‘solder sucker’ to get it off

Adding more solder to remove something is the easiest way most of the time ;) Especially if you have solder with lead and they used (horrible) lead-free. And the extra solder help transferring the heat to the component quicker so it's easier to remove it quick. So good job! :) And luckily you don't need to reuse the resistor or the pads and the board can handle a bit of abuse ;)

Hmm, more volts = less amperage? 6.3V = 380mA 10.0V = 230mA 12.0V = 190mA

Did I miss something

( But it works ! :D Finally ! )

I have no idea how you connected what and what you measure...

Sorry, crystal ball still out for repair... ;)

septillion:
I have no idea how you connected what and what you measure…

Sorry, crystal ball still out for repair… :wink:

Bottom wires of picture: Vin and Ground
Mini breadboard: High power led ground/vin

Ahhhhh, input voltage and input current, then yes! The converter is efficient!

And the laws of power state that P = U x I. So if you want the same power to the led you need less current for a higher voltage. That's why a socket has 230V on it, not just 1.

6,3V x 380mA = 2,4W 10,0V = 230mA = 2,3W 12,0V = 190mA = 2,3W

All pretty much the same. Not 100% but that's because the converter is pretty efficient but it's not 100% efficient and the efficiency depends a bit on the voltage. But it looks like the converter is more efficient on higher voltages.

septillion: Ahhhhh, input voltage and input current, then yes! The converter is efficient!

And the laws of power state that P = U x I. So if you want the same power to the led you need less current for a higher voltage. That's why a socket has 230V on it, not just 1.

6,3V x 380mA = 2,4W 10,0V = 230mA = 2,3W 12,0V = 190mA = 2,3W

All pretty much the same. Not 100% but that's because the converter is pretty efficient but it's not 100% efficient and the efficiency depends a bit on the voltage. But it looks like the converter is more efficient on higher voltages.

Ah, so the brightness will stay the same even if the current (draw?) is smaller? Weird

Also, I think it heats less with more voltage?

It's not weird. :D The current to the led is constant. But so is the voltage over the led. Which results in a constant power. And the power is what determines the brightness ;)

Looks like the regulator is more efficient at higher voltages so less heat there. For the led it's all constant so that still needs a beefy heat sink for that 2,3W.

septillion:
It’s not weird. :smiley: The current to the led is constant. But so is the voltage over the led. Which results in a constant power. And the power is what determines the brightness :wink:

Looks like the regulator is more efficient at higher voltages so less heat there. For the led it’s all constant so that still needs a beefy heat sink for that 2,3W.

This is wonderful, I just got the ‘fade’ example to work.
This is really amazing, I have been learning and planning and building and ordering stuff for like 4 months (of course doing other things in between :D), but it’s coming all together now!

Although, how beefy are we talking about?
They will be mounted inside of this glass balls (somehow) for the desk lamp (2 different balls)

Don't know exactly how big. But 2,5W of heat is not insignificant.

Most of the time I just try stuff and test if the temperature is alright. A led is terrible at heat so things must stay touchable.

Got stuck with the project (wires :D) and starting again!

Thinner cables mean, 2 wires less.

So a question arises: can I use common ground? Instead of using 6 wires per led, I could use 4?