As is well known, I'm a tremendous klutz. If you don't believe me, search my previous threads where I dropped a xp-e2 on a noctigon in a glass of water, or ask my friends and family. In any case, while attempting to install this LD-B4 buck driver: http://intl-outdoor.com/ld4b-24a-17mm-buck-driver-3v16v-p-817.html I somehow knocked the capacitor off nearest to the Led+ lead, and sadly could not find it :(( :
The two solder blobs just southeast of the R10 resistor are where the capacitor used to be.
Is there any way to remedy this without having an identical capacitor? They're not really labeled, I have some similar looking capacitors from another project, but I have no idea what value they are, or what value the capacitor is I knocked off. It looked just like the one between the resistor and the edge of the induction coil in the photo, except larger. I am hoping that this was to control mode memory, and maybe the driver will function except without modes? What would happen if I inserted a random capacitor in its place? Could I bridge it with wire/solder instead? Is there another alternative besides scrapping the driver? Any ideas before I just fire it up and see what happens?
Tried searching the forum and the net for a schematic of the driver that might reveal that capacitor's function, but to no avail. If it makes any difference, this particular one came from mtnelectronics, and the capacitor that is front and center in their photo is the same one I knocked off.
However, the picture on mtn's site does not have the smaller capacitor next to the R100 (not the one I knocked off), but two open solder blobs instead. Can anyone shed a bit of light on this? :D
I did, and his response was quick and helpful: “Yes, that’s salvageable. You need a ~1uF 16V+ 1206 capacitor. It will actually run without that capacitor most of the time, but there will be more output ripple. If you order more let me know in the checkout comments and I’ll throw a capacitor in there for you this time.”
Apparently the driver will work without the cap, it will just increase ripple (something I’ll have to google. He even offered to include another capacitor in my next order! Just another strong recommendation for mtnelectronics.com
mountainair26, now that you're into it, you may aswell ask Richard to include a bigger capacitor, or a couple of pieces. After all, the cost of the capacitor is insignificant, yet its impact will be more noticeable if once you raise the driving current.
Thanks, I might try some I have lying around tonight. Would using a larger capacitor in this spot on the board make output current increase? Speculation welcome
If not, are there any relatively easy/quick mods for this common driver to increase the current? I planned to use it for a red Xp-e2 so 2.4A is plenty in that application, but I like buck drivers in general for efficiency (I think?), so being able to mod it for higher output use with another led would be great.
mountainair26, the bigger capacitor suggestion was intended to reduce ripple, because if you are to increase the driving current, ripple will increase aswell. If the default driving current is 2.4A, a second cap in parallel would do good for up to twice that output figure with regards to ripple.
Increasing the driving current is relatively easy for these drivers. Notice the onboard sensing resistor(s), and calculate the sense voltage. All I can see is an R100, which means 0.24V sense voltage. So, if you want to raise the driving current to 4A, you need an additional 1.6A, which can be achieved by soldering an R150 (0.15Ω) resistor stacked over the R100. Alternatively, two R330s would set it to 3.85͡4͡A. I = V / R.
