Look at the R300 resistor, and the one next to it?
LED current formula is 100/R in mA.
So R300 (0.3ohm) = 100/0.3 = 333mA (1watt).
There might be one next to it.
If that one is also R300, then total LED current is 666mA (2watt).
There is a bridge rectifier on the board (D1-4) that must be bypassed if you want to dim the board.
Just connect LED supply directly to the cap.
Dim pin is pin8. The pin on the corner of the chip near the word "OUT".
Can connect directly to an Arduino output (PWM) pin.
Share grounds.
Leo..
Ok well, this nice new discovery helps me alot. I was impressed what that awesome board on #10. I am too impatient to design my own constant-current power supplies, then wait another 6 weeks to have the parts - pushing my ceiling project way longer than I want. With these affordable pre-made driver boards that I can modify makes it easier for me. I am also trying to design my headlights, fog and flood-lights for my 4x4 and knowing how to drive these currents (and save money) is important to me.
I am not familiar with surface mount components, everything I make is DIP. I can see:
(R2) "R300" and (R1) "R200"
There are (5) diodes? labeled (D1-D5) "SS24".
(C1) capacitor? I can not read value - is off/brown khaki color
On the reverse side of the module, is:
(L1) "560" coil
A GREEN/GOLD 220-uf 35v capacitor 105c.
Does GREEN/GOLD usually mean a higher quality LOW-ESR capacitor?
Are the resistors rated for 1/4 watt - or do I need to buy MORE resistors again, since my rack of 100 drawers for resistors isn't big enough?
300 & 200 resistors, so that means my module is setup for 3 watts. The eBay listing claims "10 WATTS". OMG, I am going to demand my $.78 back I've been robbed (lol)!
For the DIMMING: You say I need to bypass these 4 diodes (D1-4). My module has 5 diodes. I already put a 10k ohm resistor between chip ground & that DIM-8 pin, and it caused the LED to turn off - without undoing any of the diodes.
If there is an R300 and R200 on the module, then current is (100/0.3)+(100/0.2)=333+500=833mA.
About 2.5watt per LED in the string. Ok for 3watt LEDs.
Calculate a LED Vf (working voltage) of ~3.3volt, and a minimum of 2volt for the regulator.
Then on a 12volt supply, (one to) three LEDs can be used in series (=7.5watt total).
And on a 24volt supply, (four to) six LEDs can be used in series (=15watt total).
The SS24 has a rating of 2Amp/40volt.
The four with the same orientation is the bridge rectifier.
Just heat them up with the soldering iron for 3-4 seconds per side, and they will fall of quickly.
The supply connects to the 220u/35volt cap.
Low ESR cap because of the ~500kHz switching frequency.
Leave the current sense resistors, unless you want to lower LED current.
They swipe off as easy as the diodes. Don't use force!
The bridge is there because this module is designed for transformer based (AC) halogen light > LED replacement.
The bridge rectifier drops ~1volt. Not enough voltage left for the module with 3LEDs on a 12volt DC supply.
Not sharing supply ground with Arduino ground could introduce other problems, so remove.
Leo..
Ok, I removed the 4 diodes like you said. I shorted two leads from my +12v line IN to the + line on the capacitor, and GND line in, to the - line on capacitor. Plug everything in, and it works - perfect. My meter reads .834a, EXACTLY as you calculated.
Thanks alot! Now hopefully I can get some decent lights in this room, I've only dragged this project out for about 2 months.
If I want to make this circuit myself, I had a question about the coil on there. For that COIL, can I
just use ANY "56uh" inductor, or must I order special ones of that too? There is a "560" printed on the surface mount coil on my sample board. The data sheet uses a 68uh coil in the example.
These coils are affordable, but they do not look anything like the un-shielded coil on the board:
Coil saturation current needs to be at least ~30% higher than LED current.
That excudes the first link, and probably also the second one.
The third magnetically shielded 12*12mm coil is perfect for LED currents up to ~1Amp.
Easy so solder short wires to those coils to make them 'through hole'.
For LED currents of ~600mA, you 'should' use a 47uH coil (see PT4115 datasheet, page 12).
I have used the "47uH 10x10 shielded" variety for 0.66A (2watt/LED).
Leo..
I am a newbie when it comes to working with coils, and calculations. A "561" on the marking appears to be "560uh" and a "560" marking is "56uh". How are you calculating the math of 600ma current to get "47uh"?
(50) shielded 68uh costs me $7.00. (50) shielded 56uh coils appear to be more rare and costly.
If more is better, I guess the 68uh coils would be more useful for something else besides specifically 10 watts on this LED driver, yes?
Just like resistors. The first two digits, followed by the number of zeroes.
"680" = 68 with zero zeroes.
Datasheet table page 12.
Values are not that critical, unless you want highest efficiency possible.
But for that you also want the best possible match between supply voltage and # of LEDs in a string.
The link shows the non-shielded variety (used on most cheap LED driver boards).
Use 68uH for <= 1watt/LED (333mA), and 47uH for 1-2watt/LED (666mA).
47uH might be still ok for 3watt LEDs (1Amp).
Leo..
Ok so, I put everything together, and my system appears to work. Everything tests O.K., except (2) of my recessed LED light fixtures return a ground or positive on continuity test. So I go into my spare-parts box, and pull out 2 of the COB led fixtures labeled "6 watts". The COB LED recessed ceiling fixtures are definitely nicer - but I only have 2.
So I go hook them up, and am presented with more problems. The COB LED's are too dim! I check my hardware, it's not that. I hook up the 120v-to-LED convert box that came with it, the LED works. I test voltage while LED is on, 15.86 volts.... I guess this is the forward voltage ?
Are you running the COB led lights ? What voltage are you running them at?
The default LED string length for COB lights seems to be going to 10 (Vf ~33-36volt).
Mains power lighting could be anything.
I try to use 6-string downlights (~18-19volt), to use with a 24volt supply. Not easy to find though.
Sometimes you can split the LED strings in half, and use the two strings in parallel.
Done that with a bunch of 60-LED (12watt) downlights.
Sometimes you they get it wrong.
Ordered some 6watt (advertised) downlights from China, and they were 3watt (measured).
Went straight in the bin.
Leo..