I have done several trunk/dome light installs using the cheap LM2596 boards with the equally cheap '10W' 3x3 LED arrays. No extra components, just the original power/ground wiring feeding the board, and all are still working great. If you need a remote dimmer, the onboard pot can be removed and replaced with an offboard pot. There's also a blank spot on the board (right beside the pot) for a 0805 limiting resistor, to set the max voltage available from the main adjuster.
LM2596 boards are great, but don’t put out enough current for what I want to do. Do you know if there is a reasonably priced larger version?
That looks like something I can make work for now, Thanks!
I have no clue what I am looking at, but TI’s LM34 series (LM3421/23) might be what you are looking for.
If I’m not mistaken, the 3421 and 3423 can only provide one amp. I think for now I’ll try a buck supply like drivex suggested with 7135s to limit current until someone can help me design a new driver
it says 5 amp max on the TI website, but IDK if that is real world or not.
If you intend to do current limiting, my opinion is that while adding 7135s after a voltage-controlled buck circuit will work, it’s a big waste of energy and effort.
Buck regulators can either be voltage or current controlled. You should simply get a current controlled one instead. Here is an 10A example. Here is a cheaper, lower powered one at 4.5A. Bear in mind that you don’t want to be pushing the envelope with these, they probably generate a lot of heat when you run them at the highest current they support.
The DC/DC converters have potentiometers to set the voltage/current limits, no 7135s required or possible.
Oops, my mistake! I overlooked that the existing buck suggestion was already CC/CV. Any of those 3 should be capable of driving an MT-G2 at a set current.
If you buy the one I suggested, you can connect the leds directly to it. One trimmer is for voltage limit and the other is for current. You can find out which is the voltage one by running it without a load and trying which trimmer can adjust the output voltage. If you want to use it as a constant current driver, set the voltage to maximum and current trimmer to minimum. Then connect it to the led(s) with amp meter in circuit and adjust the current with the current trimmer.
This goes for any CC/CV driver you purchase. When dealing with the ultra-cheap and badly labeled products, keep an eye out for the number of pots/trimmers onboard: if it doesn’t have at least 2 then it’s probably a constant voltage setup.
Sure. Also if you want to connect more MT-Gs to one driver, wire it in parallel. After setting the current make sure to set the voltage trimmer as low as possible not to limit the current but close to it. Do it just to make sure that if any of those leds fails, the driver won’t damage other leds.
For example - You will connect three leds to it and set the current to 9 A (3 A for each one) if one of the leds failed and the voltage trimmer was set to max, the driver would increase the voltage as high as possible to force 9 A current through those 2 working leds. If you set the maximum output voltage to lets say 7 V, there is almost no chance of damaging the other leds. Is that clear?
(You may also ask why in parallel if you want to use just two MT-Gs? Because the driver needs some voltage reserve for its function and two MT-G leds need whole 12 V)
Anyone have a tips on where to cut in a pwm feed on these types of modules?
If you’re looking for a high current cc driver designed to survive the high voltage spikes from an alternator, there seems to be only one available at this time. Check the link in my first post for “DIWdiver” in my light bar build thread. Contact him directly through the other forum and you’ll receive an extremely detailed response. One or more of these drivers should easily suit your needs, and with the added benefit of thermal management for the emitters & driver plus over voltage protection.
You could also use a boost driver in that situation. I don’t know but I assume that with a maximum of 60v on the input that this sort of driver would also be happy to handle any spikes the alternator might throw out. EDIT: (you might want to purchase from a different seller though. The one I linked has <97% positive feedback. There are many sellers to choose from for a similar 600W boost unit)
Boost is really not needed in this application. You just loose efficiency.
ehhh… high efficiency boost circuits are possible. I’m not sure that the ones I linked are the greatest, but bucking down from 12-14v to 7v is definitely not going to get you into the best range for a buck driver. The higher the output current, the worse it gets - putting a bunch of MT-G2 LEDs in parallel is going to add up.
Compare the data posted on the TaskLED website to get an idea of what I’m talking about. Come to think of it, why haven’t I brought up TaskLED as an option?! Seems like I always do.
The HyperBoost can do 3.2A and 80v. TaskLED says it’s tested through 130W, so 3.2A @ 40v. In an automotive application you’re looking at 85-91% efficiency for this driver when driving between 5 and 1 MT-G2s.
The H6CC can do 6.7A at <Vin. This one takes a little more interpretation due to the presentation of the data, but I’d say we’re looking at ~88% efficiency when driving a pair of MT-G2 in parallel at 6.7A total or maybe 91% efficiency when driving a single MT-G2 at 3A.
Really in any application you want Vin to be relatively close to Vout, but it’s not always practical and you must balance that with keeping current under control… the higher the current the more the losses….
The TaskLED drivers are a little pricier, but they both look like decent options for this project, depending.
I have not found any indication the generic Chinese LM2596 boards aren't completely happy in an automotive environment. I've seen just about every obscure, bizarre failure that can happen to a car and from my experience these oft-mentioned dangerous voltage spikes should cause about as much concern as an attack by a rabid unicorn or a cosmic ray strike.
Comfychair:
I’m not a huge fan of using the 2596 at that high of a current. In my experience with them they are only suited for maybe 2 amps before heat becomes a factor. I’ll eventually be running at least 3 MT-G2s at around 5 amps
Musicmagic:
Looks like I may have misinterpreted that datasheet, the first time I checked them out I was on my phone. Looks like they might be a viable solution. I’ll have to do a bit more reading.
drivex, wight:
I think for now those converters are the best option. I’ll probably end up getting a few different models and designing a slightly modified version with set volatge and current once I finish prototyping my project.
ima4wheelr:
I’d imagine it wouldn’t be too hard to pwm one of those converter boards with a transistor and a little probing around with a scope. I’ll mess around with the boards I get and post my results
flashpilot:
Thats exactly the sort of thing I was looking for. That one probably won’t work for where I want to take this project, but its a step in the right direction. Having that design to reference certainly helps
If anyone wants to take me up on my offer of 502b hosts shoot me a pm with your info and I’ll order them (or whatever else you want thats in that price range). This project should make a little bit of money and I really appreciate the help. I’m going to hold off on giving out any more until I get some boards in hand and make some lumens 
Yes yes, I know. Just letting you know if it's not for something that will cause a crash if it fails (which if it is you probably shouldn't mess with it anyway), the 'automotive grade' requirement is probably not necessary. Plain off the shelf stuff works fine. Make sure it's properly fused and the worst-case failure means it'll just stop working.